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:godmode: Ultimate list of Linux bash commands # Ultimate list of Linux bash commands_Bash is the Unix command-line interface (CLI). Also called the terminal, the command line, or the shell. It's a command language that allows us to work with files on our computers in a way that's far more efficient and powerful than using a GUI (graphical user interface)_ A to Z command list 📚 > **Note** > Use `Ctrl+f` to search in browsers🔎 Table #### │ [A](#-a) │ [B](#-b) │ [C](#-c) │ [D](#-d) │ [E](#-e) │ [F](#-f) │ [G](#-g) │ [H](#-h) │ [I](#-i) │ [J](#-j) │ [K](#-k) │ [L](#-l) │ [M](#-m) │ [N](#-n) │ [O](#-o) │ [P](#-p) │ [Q](#-q) │ [R](#-r) │ [S](#-s) │ [T](#-t) │ [U](#-u) │ [V](#-v) │ [W](#-w) │ [X](#-x) │ [Y](#-y) │ [Z](#-z) │ A Command Description accept Accept or Reject jobs to a destination, such as a printer. access Check a user’s RWX permission for a file. aclocal GNU autoconf tool. aconnect ALSA sequencer connection manager. acpi Show information about the Advanced Configuration and Power Interface. acpi_available Check if ACPI functionality exists on the system. acpid Informs user-space programs about ACPI events. addr2line Used to convert addresses into file names and line numbers. addresses Formats for internet mail addresses. agetty An alternative Linux Getty. alias Create an alias for Linux commands. alsactl Access advanced controls for ALSA soundcard driver. amidi Perform read/write operation for ALSA RawMIDI ports. amixer Access CLI-based mixer for ALSA soundcard driver. anacron Used to run commands periodically. aplay Sound recorder and player for CLI. aplaymidi CLI utility used to play MIDI files. apm Show Advanced Power Management (APM) hardware info on older systems. apmd Used to handle events reported by APM BIOS drivers. apropos Shows the list of all man pages containing a specific keyword. apt Advanced Package Tool, a package management system for Debian and derivatives. apt-get Command-line utility to install/remove/update packages based on APT system. aptitude Another utility to add/remove/upgrade packages based on the APT system. ar A utility to create/modify/extract from archives. arch Display print machine hardware name. arecord Just like aplay, it’s a sound recorder and player for ALSA soundcard driver. arecordmidi Record standard MIDI files. arp Used to make changes to the system’s ARP cache. as A portable GNU assembler. aspell An interactive spell checker utility. at Used to schedule command execution at specified date & time, reading commands from an input file. atd Used to execute jobs queued by the at command. atq List a user’s pending jobs for the at command. atrm Delete jobs queued by the at command. audiosend Used to send an audio recording as an email. aumix An audio mixer utility. autoconf Generate configuration scripts from a TEMPLATE-FILE and send the output to standard output. autoheader Create a template header for configure. automake Creates GNU standards-compliant Makefiles from template files. autoreconf Update generated configuration files. autoscan Generate a preliminary configure.in file. autoupdate Update a configure.in file to newer autoconf. awk Used to find and replace text in a file(s). [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) B Command Description badblocks Search a disk partition for bad sectors. banner Used to print characters as a poster. basename Used to display filenames with directory or suffix. bash GNU Bourne-Again Shell. batch Used to run commands entered on a standard input. bc Access the GNU bc calculator utility. bg Send processes to the background. biff Notify about incoming mail and sender’s name on a system running comsat server. bind Used to attach a name to a socket. bison A GNU parser generator, compatible with yacc. break Used to exit from a loop (eg: for, while, select). builtin Used to run shell builtin commands, make custom functions for commands extending their functionality. bzcmp Used to call the cmp program forbzip2 compressed files. bzdiff Used to call the diff program for bzip2 compressed files. bzgrep Used to call grep for bzip2 compressed files. bzip2 A block-sorting file compressor used to shrink given files. bzless Used to apply ‘less’ (show info one page at a time) to bzip2 compressed files. bzmore Used to apply ‘more’ (an inferior version of less) to bzip2 compressed files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) C Command Description cal Show calendar. cardctl Used to control PCMCIA sockets and select configuration schemes. cardmgr Keeps an eye on the added/removes sockets for PCMCIA devices. case Execute a command conditionally by matching a pattern. cat Used to concatenate files and print them on the screen. cc GNU C and C++ compiler. cd Used to change directory. cdda2wav Used to rip a CD-ROM and make WAV file. cdparanoia Record audio from CD more reliably using data-verification algorithms. cdrdao Used to write all the content specified to a file to a CD all at once. cdrecord Used to record data or audio compact discs. cfdisk Show or change the disk partition table. chage Used to change user password information. chattr Used to change file attributes. chdir Used to change active working directory. chfn Used to change real user name and information. chgrp Used to change group ownership for file. chkconfig Manage execution of runlevel services. chmod Change access permission for a file(s). chown Change the owner or group for a file. chpasswd Update password in a batch. chroot Run a command with root directory. chrt Alter process attributed in real-time. chsh Switch login shell. chvt Change foreground virtual terminal. cksum Perform a CRC checksum for files. clear Used to clear the terminal window. cmp Compare two files (byte by byte). col Filter reverse (and half-reverse) line feeds from the input. colcrt Filter nroff output for CRT previewing. colrm Remove columns from the lines of a file. column A utility that formats its input into columns. comm Used to compare two sorted files line by line. command Used to execute a command with arguments ignoring shell function named command. compress Used to compress one or more file(s) and replacing the originals ones. continue Resume the next iteration of a loop. cp Copy contents of one file to another. cpio Copy files from and to archives. cpp GNU C language processor. cron A daemon to execute scheduled commands. crond Same work as cron. crontab Manage crontab files (containing schedules commands) for users. csplit Split a file into sections on the basis of context lines. ctags Make a list of functions and macro names defined in a programming source file. cupsd A scheduler for CUPS. curl Used to transfer data from or to a server using supported protocols. cut Used to remove sections from each line of a file(s). cvs Concurrent Versions System. Used to track file versions, allow storage/retrieval of previous versions, and enables multiple users to work on the same file. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) D Command Description date Show system date and time. dc Desk calculator utility. dd Used to convert and copy a file, create disk clone, write disk headers, etc. ddrescue Used to recover data from a crashed partition. deallocvt Deallocates kernel memory for unused virtual consoles. debugfs File system debugger for ext2/ext3/ext4 declare Used to declare variables and assign attributes. depmod Generate modules.dep and map files. devdump Interactively displays the contents of device or file system ISO. df Show disk usage. diff Used to compare files line by line. diff3 Compare three files line by line. dig Domain Information Groper, a DNS lookup utility. dir List the contents of a directory. dircolors Set colors for ‘ls’ by altering the LS_COLORS environment variable. dirname Display pathname after removing the last slash and characters thereafter. dirs Show the list of remembered directories. disable Restrict access to a printer. dlpsh Interactive Desktop Link Protocol (DLP) shell for PalmOS. dmesg Examine and control the kernel ring buffer. dnsdomainname Show the DNS domain name of the system. dnssec-keygen Generate encrypted Secure DNS keys for a given domain name. dnssec-makekeyset Produce domain key set from one or more DNS security keys generated by dnssec-keygen. dnssec-signkey Sign a secure DNS keyset with key signatures specified in the list of key-identifiers. dnssec-signzone Sign a secure DNS zonefile with the signatures in the specified list of key-identifiers. doexec Used to run an executable with an arbitrary argv list provided. domainname Show or set the name of current NIS (Network Information Services) domain. dosfsck Check and repair MS-DOS file systems. du Show disk usage summary for a file(s). dump Backup utility for ext2/ext3 file systems. dumpe2fs Dump ext2/ext3/ext4 file systems. dumpkeys Show information about the keyboard driver’s current translation tables. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) E Command Description e2fsck Used to check ext2/ext3/ext4 file systems. e2image Store important ext2/ext3/ext4 filesystem metadata to a file. e2label Show or change the label on an ext2/ext3/ext4 filesystem. echo Send input string(s) to standard output i.e. display text on the screen. ed GNU Ed – a line-oriented text editor. edquota Used to edit filesystem quotas using a text editor, such as vi. egrep Search and display text matching a pattern. eject Eject removable media. elvtune Used to set latency in the elevator algorithm used to schedule I/O activities for specified block devices. emacs Emacs text editor command line utility. enable Used to enable/disable shell builtin commands. env Run a command in a modified environment. Show/set/delete environment variables. envsubst Substitute environment variable values in shell format strings. esd Start the Enlightenment Sound Daemon (EsounD or esd). Enables multiple applications to access the same audio device simultaneously. esd-config Manage EsounD configuration. esdcat Use EsounD to send audio data from a specified file. esdctl EsounD control program. esddsp Used to reroute non-esd audio data to esd and control all the audio using esd. esdmon Used to copy the sound being sent to a device. Also, send it to a secondary device. esdplay Use EsounD system to play a file. esdrec Use EsounD to record audio to a specified file. esdsample Sample audio using esd. etags Used to create a list of functions and macros from a programming source file. These etags are used by emacs. For vi, use ctags. ethtool Used to query and control network driver and hardware settings. eval Used to evaluate multiple commands or arguments are once. ex Interactive command exec An interactive line-based text editor. exit Exit from the terminal. expand Convert tabs into spaces in a given file and show the output. expect An extension to the Tcl script, it’s used to automate interaction with other applications based on their expected output. export Used to set an environment variable. expr Evaluate expressions and display them on standard output. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) F Command Description factor Display prime factors of specified integer numbers. false Do nothing, unsuccessfully. Exit with a status code indicating failure. fc-cache Make font information cache after scanning the directories. fc-list Show the list of available fonts. fdformat Do a low-level format on a floppy disk. fdisk Make changes to the disk partition table. fetchmail Fetch mail from mail servers and forward it to the local mail delivery system. fg Used to send a job to the foreground. fgconsole Display the number of the current virtual console. fgrep Display lines from a file(s) that match a specified string. A variant of grep. file Determine file type for a file. find Do a file search in a directory hierarchy. finger Display user data including the information listed in .plan and .project in each user’s home directory. fingerd Provides a network interface for the finger program. flex Generate programs that perform pattern-matching on text. fmt Used to convert text to a specified width by filling lines and removing new lines, displaying the output. fold Wrap input line to fit in a specified width. for Expand words and run commands for each one in the resultant list. formail Used to filter standard input into mailbox format. format Used to format disks. free Show free and used system memory. fsck Check and repair a Linux file system ftp File transfer protocol user interface. ftpd FTP server process. function Used to define function macros. fuser Find and kill a process accessing a file. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) G Command Description g++ Run the g++ compiler. gawk Used for pattern scanning and language processing. A GNU implementation of AWK language. gcc A C and C++ compiler by GNU. gdb A utility to debug programs and know about where it crashes. getent Shows entries from Name Service Switch Libraries for specified keys. getkeycodes Displays the kernel scancode-to-keycode mapping table. getopts A utility to parse positional parameters. gpasswd Allows an administrator to change group passwords. gpg Enables encryption and signing services as per the OpenPGP standard. gpgsplit Used to split an OpenPGP message into packets. gpgv Used to verify OpenPGP signatures. gpm It enables cut and paste functionality and a mouse server for the Linux console. gprof Shows call graph profile data. grep Searches input files for a given pattern and displays the relevant lines. groff Serves as the front-end of the groff document formatting system. groffer Displays groff files and man pages. groupadd Used to add a new user group. groupdel Used to remove a user group. groupmod Used to modify a group definition. groups Showthe group(s) to which a user belongs. grpck Verifies the integrity of group files. grpconv Creates agshadow file from a group or an already existing gshadow. gs Invokes Ghostscript, and interpreter and previewer for Adobe’s PostScript and PDF languages. gunzip A utility to compress/expand files. gzexe Used compress executable files in place and have them automatically uncompress and run at a later stage. gzip A utility to compress/expand files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) H Command Description halt Command used to half the machine. hash Shows the path for the commands executed in the shell. hdparm Show/configure parameters for SATA/IDE devices. head Shows first 10 lines from each specified file. help Display’s help for a built-in command. hexdump Shows specified file output in hexadecimal, octal, decimal, or ASCII format. history Shows the command history. host A utility to perform DNS lookups. hostid Shows host’s numeric ID in hexadecimal format. hostname Display/set the hostname of the system. htdigest Manage the user authentication file used by the Apache web server. htop An interactive process viewer for the command line. hwclock Show or configure the system’s hardware clock. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) I Command Description iconv Convert text file from one encoding to another. id Show user and group information for a specified user. if Execute a command conditionally. ifconfig Used to configure network interfaces. ifdown Stops a network interface. ifup Starts a network interface. imapd An IMAP (Interactive Mail Access Protocol) server daemon. import Capture an X server screen and saves it as an image. inetd Extended internet services daemon, it starts the programs that provide internet services. info Used to read the documentation in Info format. init Systemd system and service manager. insmod A program that inserts a module into the Linux kernel. install Used to copy files to specified locations and set attributions during the install process. iostat Shows statistics for CPU, I/O devices, partitions, network filesystems. ip Display/manipulate routing, devices, policy, routing and tunnels. ipcrm Used to remove System V interprocess communication (IPC) objects and associated data structures. ipcs Show information on IPC facilities for which calling process has read access. iptables Administration tool for IPv4 packet filtering and NAT. iptables-restore Used to restore IP tables from data specified in the input or a file. iptables-save Used to dump IP table contents to standard output. isodump A utility that shows the content iso9660 images to verify the integrity of directory contents. isoinfo A utility to perform directory like listings of iso9660 images. isosize Show the length of an iso9660 filesystem contained in a specified file. isovfy Verifies the integrity of an iso9660 image. ispell A CLI-based spell-check utility. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) J Command Description jobs Show the list of active jobs and their status. join For each pair of input lines, join them using a command field and display on standard output. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) K Command Description kbd_mode Set a keyboard mode. Without arguments, shows the current keyboard mode. kbdrate Reset keyboard repeat rate and delay time. kill Send a kill (termination) signal to one more processes. killall Kills a process(es) running a specified command. killall5 A SystemV killall command. Kills all the processes excluding the ones which it depends on. klogd Control and prioritize the kernel messages to be displayed on the console, and log them through syslogd. kudzu Used to detect new and enhanced hardware by comparing it with existing database. Only for RHEL and derivatives. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) L Command Description last Shows a list of recent logins on the system by fetching data from /var/log/wtmp file. lastb Shows the list of bad login attempts by fetching data from /var/log/btmp file. lastlog Displays information about the most recent login of all users or a specified user. ld The Unix linker, it combines archives and object files. It then puts them into one output file, resolving external references. ldconfig Configure dynamic linker run-time bindings. ldd Shows shared object dependencies. less Displays contents of a fileone page at a time. It’s advanced than more command. lesskey Used to specify key bindings for less command. let Used to perform integer artithmetic on shell variables. lftp An FTP utility with extra features. lftpget Uses lftop to retrieve HTTP, FTP, and other protocol URLs supported by lftp. link Create links between two files. Similar to ln command. ln Create links between files. Links can be hard (two names for the same file) or soft (a shortcut of the first file). loadkeys Load keyboard translation tables. local Used to create function variables. locale Shows information about current or all locales. locate Used to find files by their name. lockfile Create semaphore file(s) which can be used to limit access to a file. logger Make entries in the system log. login Create a new session on the system. logname Shows the login name of the current user. logout Performs the logout operation by making changes to the utmp and wtmp files. logrotate Used for automatic rotation, compression, removal, and mailing of system log files. look Shows any lines in a file containing a given string in the beginning. losetup Set up and control loop devices. lpadmin Used to configure printer and class queues provided by CUPS (Common UNIX Printing System). lpc Line printer control program, it provides limited control over CUPS printer and class queues. lpinfo Shows the list of available devices and drivers known to the CUPS server. lpmove Move on or more printing jobs to a new destination. lpq Shows current print queue status for a specified printer. lpr Used to submit files for printing. lprint Used to print a file. lprintd Used to abort a print job. lprintq List the print queue. lprm Cancel print jobs. lpstat Displays status information about current classes, jobs, and printers. ls Shows the list of files in the current directory. lsattr Shows file attributes on a Linux ext2 file system. lsblk Lists information about all available or the specified block devices. lsmod Show the status of modules in the Linux kernel. lsof List open files. lspci List all PCI devices. lsusb List USB devices. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) M Command Description m4 Macro processor. mail Utility to compose, receive, send, forward, and reply to emails. mailq Shows to list all emails queued for delivery (sendmail queue). mailstats Shows current mail statistics. mailto Used to send mail with multimedia content in MIME format. make Utility to maintain groups of programs, recompile them if needed. makedbm Creates an NIS (Network Information Services) database map. makemap Creates database maps used by the keyed map lookups in sendmail. man Shows manual pages for Linux commands. manpath Determine search path for manual pages. mattrib Used to change MS-DOS file attribute flags. mbadblocks Checks MD-DOS filesystems for bad blocks. mcat Dump raw disk image. mcd Used to change MS-DOS directory. mcopy Used to copy MS-DOS files from or to Unix. md5sum Used to check MD5 checksum for a file. mdel, mdeltree Used to delete MS-DOS file. mdeltree recursively deletes MS-DOS directory and its contents. mdir Used to display an MS-DOS directory. mdu Used to display the amount of space occupied by an MS-DOS directory. merge Three-way file merge. Includes all changes from file2 and file3 to file1. mesg Allow/disallow osends to sedn write messages to your terminal. metamail For sending and showing rich text or multimedia email using MIME typing metadata. metasend An interface for sending non-text mail. mformat Used to add an MS-DOS filesystem to a low-level formatted floppy disk. mimencode Translate to/from MIME multimedia mail encoding formats. minfo Display parameters of an MS-DOS filesystem. mkdir Used to create directories. mkdosfs Used to create an MS-DOS filesystem under Linux. mke2fs Used create an ext2/ext3/ext4 filesystem. mkfifo Used to create named pipes (FIFOs) with the given names. mkfs Used to build a Linux filesystem on a hard disk partition. mkfs.ext3 Same as mke2fs, create an ext3 Linux filesystem. mkisofs Used to create an ISO9660/JOLIET/HFS hybrid filesystem. mklost+found Create a lost+found directory on a mounted ext2 filesystem. mkmanifest Makes alist of file names and their DOS 8.3 equivalent. mknod Create a FIFO, block (buffered) special file, character (unbuffered) special file with the specified name. mkraid Used to setup RAID device arrays. mkswap Set up a Linux swap area. mktemp Create a temporary file or directory. mlabel Make an MD-DOS volume label. mmd Make an MS-DOS subdirectory. mmount Mount an MS-DOS disk. mmove Move or rename an MS-DOS file or subdirectory. mmv Mass move and rename files. modinfo Show information about a Linux kernel module. modprobe Add or remove modules from the Linux kernel. more Display content of a file page-by-page. most Browse or page through a text file. mount Mount a filesystem. mountd NFS mount daemon. mpartition Partition an MS-DOS disk. mpg123 Command-line mp3 player. mpg321 Similar to mpg123. mrd Remove an MS-DOS subdirectory. mren Rename an existing MS-DOS file. mshowfat Show FTA clusters allocated to a file. mt Control magnetic tape drive operation. mtools Utilities to access MS-DOS disks. mtoolstest Tests and displays the mtools configuration files. mtr A network diagnostic tool. mtype Display contents of an MS-DOS file. mv Move/rename files or directories. mzip Change protection mode and eject disk on Zip/Jaz drive. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) N Command Description named Internet domain name server. namei Follow a pathname until a terminal point is found. nameif Name network interfaces based on MAC addresses. nc Netcat utility. Arbitrary TCP and UDP connections and listens. netstat Show network information. newaliases Rebuilds mail alias database. newgrp Log-in to a new group. newusers Update/create new users in batch. nfsd Special filesystem for controlling Linux NFS server. nfsstat List NFS statistics. nice Run a program with modified scheduling priority. nl Show numbered line while displaying the contents of a file. nm List symbols from object files. nohup Run a command immune to hangups. notify-send A program to send desktop notifications. nslookup Used performs DNS queries. Read this article for more info. nsupdate Dynamic DNS update utility. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) O Command Description objcopy Copy and translate object files. objdump Display information from object files. od Dump files in octal and other formats. op Operator access, allows system administrators to grant users access to certain root operations that require superuser privileges. open Open a file using its default application. openvt Start a program on a new virtual terminal (VT). [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) P Command Description passwd Change user password. paste Merge lines of files. Write to standard output, TAB-separated lines consisting of sequentially corresponding lines from each file. patch Apply a patchfile (containing differences listing by diff program) to an original file. pathchk Check if file names are valid or portable. perl Perl 5 language interpreter. pgrep List process IDs matching the specified criteria among all the running processes. pidof Find process ID of a running program. ping Send ICMP ECHO_REQUEST to network hosts. pinky Lightweight finger. pkill Send kill signal to processes based on name and other attributes. pmap Report memory map of a process. popd Removes directory on the head of the directory stack and takes you to the new directory on the head. portmap Converts RPC program numbers to IP port numbers. poweroff Shuts down the machine. pppd Point-to-point protocol daemon. pr Convert (column or paginate) text files for printing. praliases Prints the current system mail aliases. printcap Printer capability database. printenv Show values of all or specified environment variables. printf Show arguments formatted according to a specified format. ps Report a snapshot of the current processes. ptx Produce a permuted index of file contents. pushd Appends a given directory name to the head of the stack and then cd to the given directory. pv Monitor progress of data through a pipe. pwck Verify integrity of password files. pwconv Creates shadow from passwd and an optionally existing shadow. pwd Show current directory. python [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Q Command Description quota Shows disk usage, and space limits for a user or group. Without arguments, only shows user quotas. quotacheck Used to scan a file system for disk usage. quotactl Make changes to disk quotas. quotaoff Enable enforcement of filesystem quotas. quotaon Disable enforcement of filesystem quotas. quotastats Shows the report of quota system statistics gathered from the kernel. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) R Command Description raidstart Start/stop RAID devices. ram RAM disk device used to access the RAM disk in raw mode. ramsize Show usage information for the RAM disk. ranlib Generate index to the contents of an archive and store it in the archive. rar Create and manage RAR file in Linux. rarpd Respond to Reverse Address Resolution Protocol (RARP) requests. rcp Remote copy command to copy files between remote computers. rdate Set system date and time by fetching information from a remote machine. rdev Set or query RAM disk size, image root device, or video mode. rdist Remote file distribution client, maintains identical file copies over multiple hosts. rdistd Start the rdist server. read Read from a file descriptor. readarray Read lines from a file into an array variable. readcd Read/write compact disks. readelf Shows information about ELF (Executable and Linkable format) files. readlink Display value of a symbolic link or canonical file name. readonly Mark functions and variables as read-only. reboot Restart the machine. reject Accept/reject print jobs sent to a specified destination. remsync Synchronize remote files over email. rename Rename one or more files. renice Change priority of active processes. repquota Report disk usage and quotas for a specified filesystem. reset Reinitialize the terminal. resize2fs Used to resize ext2/ext3/ext4 file systems. restore Restore files from a backup created using dump. return Exit a shell function. rev Show contents of a file, reversing the order of characters in every line. rexec Remote execution client for exec server. rexecd Remote execution server. richtext View “richtext” on an ACSII terminal. rlogin Used to connect a local host system with a remote host. rlogind Acts as the server for rlogin.It facilitates remote login, and authentication based on privileged port numbers from trusted hosts. rm Removes specified files and directories (not by default). rmail Handle remote mail received via uucp. rmdir Used to remove empty directories. rmmod A program to remove modules from Linux kernel. rndc Name server control utility. Send command to a BIND DNS server over a TCP connection. rootflags Show/set flags for the kernel image. route Show/change IP routing table. routed A daemon, invoked at boot time, to manage internet routing tables. rpcgen An RPC protocol compiler. Parse a file written in the RPC language. rpcinfo Shows RPC information. Makes an RPC call to an RPC server and reports the findings. rpm A package manager for Linux distributions. Originally developed for RedHat Linux. rsh Remote shell. Connects to a specified host and executes commands. rshd A daemon that acts as a server for rsh and rcp commands. rsync A versitile to for copying files remotely and locally. runlevel Shows previous and current SysV runlevel. rup Remote status display. Shows current system status for all or specified hosts on the local network. ruptime Shows uptime and login details of the machines on the local network. rusers Shows the list of the users logged-in to the host or on all machines on the local network. rusersd The rsuerd daemon acts as a server that responds to the queries from rsuers command. rwall Sends messages to all users on the local network. rwho Reports who is logged-in to the hosts on the local network. rwhod Acts as a server for rwho and ruptime commands. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) S Command Description sane-find-scanner Find SCSI and USB scanner and determine their device files. scanadf Retrieve multiple images from a scanner equipped with an automatic document feeder (ADF). scanimage Read images from image acquisition devices (scanner or camera) and display on standard output in PNM (Portable aNyMap) format. scp Copy files between hosts on a network securely using SSH. screen A window manager that enables multiple pseudo-terminals with the help of ANSI/VT100 terminal emulation. script Used to make a typescript of everything displayed on the screen during a terminal session. sdiff Shows two files side-by-side and highlights the differences. sed Stream editor for filtering and transforming text (from a file or a pipe input). select Synchronous I/O multiplexing. sendmail It’s a mail router or an MTA (Mail Transfer Agent). sendmail support can send a mail to one or more recipients using necessary protocols. sensors Shows the current readings of all sensor chips. seq Displays an incremental sequence of numbers from first to last. set Used to manipulate shell variables and functions. setfdprm Sets floppy disk parameters as provided by the user. setkeycodes Load kernel scancode-to-keycode mapping table entries. setleds Show/change LED light settings of the keyboard. setmetamode Define keyboard meta key handling. Without arguments, shows current meta key mode. setquota Set disk quotas for users and groups. setsid Run a program in a new session. setterm Set terminal attributes. sftp Secure File Transfer program. sh Command interpreter (shell) utility. sha1sum Compute and check 160-bit SHA1 checksum to verify file integrity. shift Shift positional parameters. shopt Shell options. showkey Examines codes sent by the keyboard displays them in printable form. showmount Shows information about NFS server mount on the host. shred Overwrite a file to hide its content (optionally delete it), making it harder to recover it. shutdown Power-off the machine. size Lists section size and the total size of a specified file. skill Send a signal to processes. slabtop Show kernel slab cache information in real-time. slattach Attack a network interface to a serial line. sleep Suspend execution for a specified amount of time (in seconds). slocate Display matches by searching filename databases. Takes ownership and file permission into consideration. snice Reset priority for processes. sort Sort lines of text files. source Run commands from a specified file. split Split a file into pieces of fixed size. ss Display socket statistics, similar to netstat. ssh An SSH client for logging in to a remote machine. It provides encrypted communication between the hosts. ssh-add Adds private key identities to the authentication agent. ssh-agent It holds private keys used for public key authentication. ssh-keygen It generates, manages, converts authentication keys for ssh. ssh-keyscan Gather ssh public keys. sshd Server for the ssh program. stat Display file or filesystem status. statd A daemon that listens for reboot notifications from other hosts, and manages the list of hosts to be notified when the local system reboots. strace Trace system calls and signals. strfile Create a random access file for storing strings. strings Search a specified file and prints any printable strings with at least four characters and followed by an unprintable character. strip Discard symbols from object files. stty Change and print terminal line settings. su Change user ID or become superuser. sudo Execute a command as superuser. sum Checksum and count the block in a file. suspend Suspend the execution of the current shell. swapoff Disable devices for paging and swapping. swapon Enable devices for paging and swapping. symlink Create a symbolic link to a file. sync Synchronize cached writes to persistent storage. sysctl Configure kernel parameters at runtime. sysklogd Linux system logging utilities. Provides syslogd and klogd functionalities. syslogd Read and log system messages to the system console and log files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) T Command Description tac Concatenate and print files in reverse order. Opposite of cat command. tail Show the last 10 lines of each specified file(s). tailf Follow the growth of a log file. (Deprecated command) talk A two-way screen-oriented communication utility that allows two user to exchange messages simultaneously. talkd A remote user communication server for talk . tar GNU version of the tar archiving utility. Used to store and extract multiple files from a single archive. taskset Set/retrieve a process’s CPU affinity. tcpd Access control utility for internet services. tcpdump Dump traffic on network. Displays a description of the contents of packets on a network interface that match the boolean expression. tcpslice Extract pieces of tcpdump files or merge them. tee Read from standard input and write to standard output and files. telinit Change SysV runlevel. telnet Telnet protocol user interface. Used to interact with another host using telnet. telnetd A server for the telnet protocol. test Check file type and compare values. tftp User interface to the internet TFTP (Trivial File Transfer Protocol). tftpd TFTP server. time Run programs and summarize system resource usage. timeout Execute a command with a time limit. times Shows accumulated user and system times for the shell and it’s child processes. tload Shows a graph of the current system load average to the specified tty. tmpwatch Recursively remove files and directories which haven’t been accessed for the specified period of time. top Displays real-time view of processes running on the system. touch Change file access and modification times. tput Modify terminal-dependent capabilities, color, etc. tr Translate, squeeze, or delete characters from standard input and display on standard output. tracepath Traces path to a network host discovering MTU (Maximum Transmission Unit) along this path. traceroute Traces the route taken by the packets to reach the network host. trap Trap function responds to hardware signals. It defines and creates handlers to run when the shell receives signals. troff The troff processor of the groff text formatting system. TRUE Exit with a status code indicating success. tset Initialize terminal. tsort Perform topological sort. tty Display the filename of the terminal connected to standard input. tune2fs Adjust tuneable filesystem parameters on ext2/ext3/ext4 filesystems. tunelp Set various parameters for the line printer devices. type Write a description for a command type. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) U Command Description ul Underline text. ulimit Get and set user limits for the calling process. umask Set file mode creation mask. umount Unmount specified file systems. unalias Remove alias definitions for specified alias names. uname Show system information. uncompress Uncompress the files compressed with the compress command. unexpand Convert spaces to tabs for a specified file. unicode_start Put keyboard and console in Unicode mode. unicode_stop Revert keyboard and console from Unicode mode. uniq Report or omit repeating lines. units Convert units from one scalar to another. unrar Extract files from a RAR archive. unset Remove variable or function names. unshar Unpack shell archive scripts. until Execute command until a given condition is true. uptime Tell how long the system has been running. useradd Create a new user or update default user information. userdel Delete a user account and related files. usermod Modify a user account. users Show the list of active users on the machine. usleep Suspend execution for microsecond intervals. uudecode Decode a binary file. uuencode Encode a binary file. uuidgen Created a new UUID (Universally Unique Identifier) table. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) V Command Description vdir Same as ls -l -b . Verbosely list directory contents. vi A text editor utility. vidmode Set the video mode for a kernel image. Displays current mode value without arguments. Alternative: rdev -v vim Vi Improved, a text-based editor which is a successor to vi. vmstat Shows information about processes, memory, paging, block IO, traps, disks, and CPU activity. volname Returns volume name for a device formatted with an ISO-9660 filesystem. For example, CD-ROM. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) W Command Description w Show who is logged-on and what they’re doing. wait Waits for a specified process ID(s) to terminate and returns the termination status. wall Display a message on the terminals all the users who are currently logged-in. warnquota Send mail to the users who’ve exceeded their disk quota soft limit. watch Runs commands repeatedly until interrupted and shows their output and errors. wc Print newline, word, and byte count for each of the specified files. wget A non-interactive file download utility. whatis Display one line manual page descriptions. whereis Locate the binary, source, and man page files for a command. which For a given command, lists the pathnames for the files which would be executed when the command runs. while Conditionally execute commands (while loop). who Shows who is logged on. whoami Displays the username tied to the current effective user ID. whois Looks for an object in a WHOIS database write Display a message on other user’s terminal. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) X Command Description xargs Runs a command using initial arguments and then reads remaining arguments from standard input. xdg-open Used to open a file or URL in an application preferred by the user. xinetd Extended internet services daemon. Works similar to inetd. xz Compress/ Decompress .xz and .lzma files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Y Command Description yacc Yet Another Compiler Compiler, a GNU Project parser generator. yes Repeatedly output a line with a specified string(s) until killed. ypbind A daemon that helps client processes to connect to an NIS server. ypcat Shows the NIS map (or database) for the specified MapName parameter. ypinit Sets up NIS maps on an NIS server. ypmatch Shows values for specified keys from an NIS map. yppasswd Change NIS login password. yppasswdd Acts as a server for the yppasswd command. Receives and executes requests. yppoll Shows the ID number or version of NIS map currently used on the NIS server. yppush Forces slave NIS servers to copy updated NIS maps. ypserv A daemon activated at system startup. It looks for information in local NIS maps. ypset Point a client (running ypbind) to a specific server (running ypserv). yptest Calls various functions to check the configuration of NIS services. ypwhich Shows the hostname for NIS server or master server for a given map. ypxfr Transfers NIS server map from server to a local host. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Z Command Description zcat Used to compress/uncompress files. Similar to gzip zcmp Compare compressed files. zdiff Compare compressed files line by line. zdump Displays time for the timezone mentioned. zforce Adds .gz extension to all gzipped files. zgrep Performs grep on compressed files. zic Creates time conversion information files using the specified input files. zip A file compression and packaging utility. zless Displays information of a compressed file (using less command) on the terminal one screen at a time. zmore Displays output of a compressed file (using more command) on the terminal one page at a time. znew Recompress .z files to .gz. files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Quick cheat sheet 📝 >**Note** > Examples like `-a|--all` option flags means, single `-` used for _short_ option(-a) **or**| double `--` used for _long_ option(--all). Both was added for educational purpose.### Contents- [Command Information](#command-information)- [Command History](#command-history)- [Navigating Directories](#navigating-directories)- [Creating Directories](#creating-directories)- [Moving Directories](#moving-directories)- [Deleting Directories](#deleting-directories)- [Creating Files](#creating-files)- [Standard Output, Error and Input](#standard-output-standard-error-and-standard-input)- [Moving Files](#moving-files)- [Deleting Files](#deleting-files)- [Reading Files](#reading-files)- [File Permissions](#file-permissions)- [Finding Files](#finding-files)- [Find in Files](#find-in-files)- [Replace in Files](#replace-in-files)- [Symbolic Links](#symbolic-links)- [Compressing Files](#compressing-files)- [Decompressing Files](#decompressing-files)- [Packages](#packages)- [Disk Usage](#disk-usage)- [Memory Usage](#memory-usage)- [Shutdown and Reboot](#shutdown-and-reboot)- [Identifying Processes](#identifying-processes)- [Process Priority](#process-priority)- [Killing Processes](#killing-processes)- [Date & Time](#date--time)- [Scheduled Tasks](#scheduled-tasks)- [User Mangement](#user-management)- [HTTP Requests](#http-requests)- [Network Troubleshooting](#network-troubleshooting)- [DNS](#dns)- [Hardware](#hardware)- [System Information](#system-information)- [Terminal Multiplexers](#terminal-multiplexers)- [Secure Shell Protocol (SSH)](#secure-shell-protocol-ssh)- [Secure Copy](#secure-copy)- [Bash Profile](#bash-profile)- [Bash Script](#bash-script)### Command Information```bashman chmod # Display page manual of a commandman -f|--whatis chmod # Display short description about a commandman -k|--apropos permission # Display all related commands from a specific keywordchmod --help # Display usage options of a command```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Command History```bashhistory # View all previous commandshistory | grep foo # View the commands using a specific wordhistory | grep -E|--extended-regexp -i|--ignore-case 'foo1|foo2|foo3' # View the commands using more than 1 specific word(case sensitive)history | head -n|--lines 3 # View the first 3 executed commandshistory 3 # View the last 3 executed commandshistory -d 99 # Clear a command from a specific line history -c # Clears all history commands!! # Run the last command executedtouch foo.sh # <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<┐chmod +x !$ # !$ is the last argument of the last command i.e. foo.sh <<<<┘```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Navigating Directories```bashpwd # Print current directory pathls # List directoriesls -a|--all # List directories including hiddenls -l # List directories in long formls -l -h|--human-readable # List directories in long form with human readable sizesls -t # List directories by modification time, newest firststat foo.txt # List size, created and modified timestamps for a filestat foo # List size, created and modified timestamps for a directorytree # List directory and file treetree -a # List directory and file tree including hiddentree -d # List directory treecd foo # Go to foo sub-directorycd # Go to home directorycd ~ # Go to home directorycd - # Go to last directorypushd foo # Go to foo sub-directory and add previous directory to stackpopd # Go back to directory in stack saved by `pushd````[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Creating Directories ```bashmkdir foo # Create a directorymkdir foo bar # Create multiple directoriesmkdir -p|--parents foo/bar # Create nested directorymkdir -p|--parents {foo,bar}/baz # Create multiple nested directoriesmktemp -d|--directory # Create a temporary directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Moving Directories```bashcp -R|--recursive foo bar # Copy directorymv foo bar # Move directoryrsync -z|--compress -v|--verbose /foo /bar # Copy directory, overwrites destinationrsync --ignore-existing -a|--archive-a|--archive -z|--compress -v|--verbose /foo /bar # Copy directory, without overwriting destinationrsync -avz /foo username@hostname:/bar # Copy local directory to remote directoryrsync -avz username@hostname:/foo /bar # Copy remote directory to local directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Deleting Directories```bashrmdir foo # Delete non-empty directoryrm -r|--recursive foo # Delete directory including contentsrm -r|--recursive -f|--force foo # Delete directory including contents, ignore nonexistent files and never prompt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Creating Files```bashtouch foo.txt # Create file or update existing files modified timestamptouch foo.txt bar.txt # Create multiple filestouch {foo,bar}.txt # Create multiple filestouch test{1..3} # Create test1, test2 and test3 filestouch test{a..c} # Create testa, testb and testc filesmktemp # Create a temporary file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Standard Output, Standard Error and Standard Input```bashecho "foo" > bar.txt # Overwrite file with contentecho "foo" >> bar.txt # Append to file with contentls exists 1> stdout.txt # Redirect the standard output to a filels noexist 2> stderror.txt # Redirect the standard error output to a filels > out.txt 2>&1 # Redirect standard output and error to a filels > /dev/null # Discard standard output and errorread foo # Read from standard input and write to the variable foo```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Moving Files```bashcp foo.txt bar.txt # Copy filemv foo.txt bar.txt # Move filersync -z|--compress -v|--verbose /foo.txt /bar # Copy file quickly if not changedrsync -z|--compress -v|--verbose /foo.txt /bar.txt # Copy and rename file quickly if not changed```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Deleting Files```bashrm foo.txt # Delete filerm -f|--force foo.txt # Delete file, ignore nonexistent files and never prompt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Reading Files```bashcat foo.txt # Print all contentsless foo.txt # Print some contents at a time (g - go to top of file, SHIFT+g, go to bottom of file, /foo to search for 'foo')head foo.txt # Print top 10 lines of filetail foo.txt # Print bottom 10 lines of filetail -f foo.txt # Print bottom 10 lines of file updating with new dataopen foo.txt # Open file in the default editorwc foo.txt # List number of lines words and characters in the file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## File Permissions| # | Permission | rwx | Binary || - | - | - | - || 7 | read, write and execute | rwx | 111 || 6 | read and write | rw- | 110 || 5 | read and execute | r-x | 101 || 4 | read only | r-- | 100 || 3 | write and execute | -wx | 011 || 2 | write only | -w- | 010 || 1 | execute only | --x | 001 || 0 | none | --- | 000 |For a directory, execute means you can enter a directory.| User | Group | Others | Description || - | - | - | - || 6 | 4 | 4 | User can read and write, everyone else can read (Default file permissions) || 7 | 5 | 5 | User can read, write and execute, everyone else can read and execute (Default directory permissions) |- u - User- g - Group- o - Others- a - All of the above```bashls -l /foo.sh # List file permissionschmod +100 foo.sh # Add 1 to the user permissionchmod -100 foo.sh # Subtract 1 from the user permissionchmod u+x foo.sh # Give the user execute permissionchmod g+x foo.sh # Give the group execute permissionchmod u-x,g-x foo.sh # Take away the user and group execute permissionchmod u+x,g+x,o+x foo.sh # Give everybody execute permissionchmod a+x foo.sh # Give everybody execute permissionchmod +x foo.sh # Give everybody execute permission```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Finding FilesFind binary files for a command.```bashtype -a wget # Display all locations of executablewhich -a wget # Display all locations of executables whereis wget # Find the binary, source, and manual page files````locate` uses an index and is fast.```bashupdatedb # Update the indexlocate foo.txt # Find a filelocate --ignore-case # Find a file and ignore caselocate f*.txt # Find a text file starting with 'f'````find` doesn't use an index and is slow.```bashfind /path -name foo.txt # Find a filefind /path -iname foo.txt # Find a file with case insensitive searchfind /path -name "*.txt" # Find all text filesfind /path -name foo.txt -delete # Find a file and delete itfind /path -name "*.png" -exec pngquant {} # Find all .png files and execute pngquant on itfind /path -type f -name foo.txt # Find a filefind /path -type d -name foo # Find a directoryfind /path -type l -name foo.txt # Find a symbolic linkfind /path -type f -mtime +30 # Find files that haven't been modified in 30 daysfind /path -type f -mtime +30 -delete # Delete files that haven't been modified in 30 days```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Find in Files```bashgrep 'foo' /bar.txt # Search for 'foo' in file 'bar.txt'grep 'foo' /bar -r|--recursive # Search for 'foo' in directory 'bar'grep 'foo' /bar -R|--dereference-recursive # Search for 'foo' in directory 'bar' and follow symbolic linksgrep 'foo' /bar -l|--files-with-matches # Show only files that matchgrep 'foo' /bar -L|--files-without-match # Show only files that don't matchgrep 'Foo' /bar -i|--ignore-case # Case insensitive searchgrep 'foo' /bar -x|--line-regexp # Match the entire linegrep 'foo' /bar -C|--context 1 # Add N line of context above and below each search resultgrep 'foo' /bar -v|--invert-match # Show only lines that don't matchgrep 'foo' /bar -c|--count # Count the number lines that matchgrep 'foo' /bar -n|--line-number # Add line numbersgrep 'foo' /bar --colour # Add colour to outputgrep 'foo\|bar' /baz -R # Search for 'foo' or 'bar' in directory 'baz'grep --extended-regexp|-E 'foo|bar' /baz -R # Use regular expressionsgrep -E 'foo|bar' /baz -R # Use regular expressions```### Replace in Files```bashsed 's/fox/bear/g' foo.txt # Replace fox with bear in foo.txt and output to consolesed 's/fox/bear/gi' foo.txt # Replace fox (case insensitive) with bear in foo.txt and output to consolesed 's/red fox/blue bear/g' foo.txt # Replace red with blue and fox with bear in foo.txt and output to consolesed 's/fox/bear/g' foo.txt > bar.txt # Replace fox with bear in foo.txt and save in bar.txtsed 's/fox/bear/g' foo.txt -i|--in-place # Replace fox with bear and overwrite foo.txt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Symbolic Links```bashln -s|--symbolic foo bar # Create a link 'bar' to the 'foo' folderln -s|--symbolic -f|--force foo bar # Overwrite an existing symbolic link 'bar'ls -l # Show where symbolic links are pointing```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Compressing Files### zipCompresses one or more files into *.zip files.```bashzip foo.zip /bar.txt # Compress bar.txt into foo.zipzip foo.zip /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.zipzip foo.zip /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.zipzip -r|--recurse-paths foo.zip /bar # Compress directory bar into foo.zip```### gzipCompresses a single file into *.gz files.```bashgzip /bar.txt foo.gz # Compress bar.txt into foo.gz and then delete bar.txtgzip -k|--keep /bar.txt foo.gz # Compress bar.txt into foo.gz```### tar -cCompresses (optionally) and combines one or more files into a single *.tar, *.tar.gz, *.tpz or *.tgz file.```bashtar -c|--create -z|--gzip -f|--file=foo.tgz /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.tgztar -c|--create -z|--gzip -f|--file=foo.tgz /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.tgztar -c|--create -z|--gzip -f|--file=foo.tgz /bar # Compress directory bar into foo.tgz```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Decompressing Files### unzip```bashunzip foo.zip # Unzip foo.zip into current directory```### gunzip```bashgunzip foo.gz # Unzip foo.gz into current directory and delete foo.gzgunzip -k|--keep foo.gz # Unzip foo.gz into current directory```### tar -x```bashtar -x|--extract -z|--gzip -f|--file=foo.tar.gz # Un-compress foo.tar.gz into current directorytar -x|--extract -f|--file=foo.tar # Un-combine foo.tar into current directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Packages```bashapt update # Refreshes repository indexapt search wget # Search for a packageapt show wget # List information about the wget packageapt list --all-versions wget # List all versions of the packageapt install wget # Install the latest version of the wget packageapt install wget=1.2.3 # Install a specific version of the wget packageapt remove wget # Removes the wget packageapt upgrade # Upgrades all upgradable packagesapt clean # Clears out the local repository of downloaded package filesdpkg -i|--install package_name.deb # Install deb filerpm -i|--install package_name.rpm # Install rpm file ```### Install package source code```bashtar zxvf sourcecode.tar.gzcd sourcecode./configuremakemake install```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Disk Usage```bashdf # List disks, size, used and available spacedf -h|--human-readable # List disks, size, used and available space in a human readable formatdu # List current directory, subdirectories and file sizesdu /foo/bar # List specified directory, subdirectories and file sizesdu -h|--human-readable # List current directory, subdirectories and file sizes in a human readable formatdu -d|--max-depth # List current directory, subdirectories and file sizes within the max depthdu -d 0 # List current directory size```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Memory Usage```bashfree # Show memory usagefree -h|--human # Show human readable memory usagefree -h|--human --si # Show human readable memory usage in power of 1000 instead of 1024free -s|--seconds 5 # Show memory usage and update continuously every five seconds```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Shutdown and Reboot```bashshutdown # Shutdown in 1 minuteshutdown now # Immediately shut downshutdown +5 # Shutdown in 5 minutesshutdown -r|--reboot # Reboot in 1 minuteshutdown -r|--reboot now # Immediately rebootshutdown -r|--reboot +5 # Reboot in 5 minutesshutdown -c # Cancel a shutdown or rebootreboot # Reboot nowreboot -f # Force a reboot```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Identifying Processes```bashtop # List all processes interactivelyhtop # List all processes interactivelyps ax # List all processespidof foo # Return the PID of all foo processesCTRL+Z # Suspend a process running in the foregroundbg # Resume a suspended process and run in the backgroundfg # Bring the last background process to the foregroundfg 1 # Bring the background process with the PID to the foregroundsleep 30 & # Sleep for 30 seconds and move the process into the backgroundjobs # List all background jobsjobs -p # List all background jobs with their PIDlsof # List all open files and the process using themlsof -itcp:4000 # Return the process listening on port 4000```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Process PriorityProcess priorities go from -20 (highest) to 19 (lowest).```bashnice -n -20 foo # Change process priority by namerenice 20 PID # Change process priority by PIDps -o ni PID # Return the process priority of PID```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Killing Processes```bashCTRL+C # Kill a process running in the foregroundkill PID # Shut down process by PID gracefully. Sends TERM signal.kill -9 PID # Force shut down of process by PID. Sends SIGKILL signal.pkill foo # Shut down process by name gracefully. Sends TERM signal.pkill -9 foo # force shut down process by name. Sends SIGKILL signal.killall foo # Kill all process with the specified name gracefully.```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Date & Time```bashdate # Print the date and timedate --iso-8601 # Print the ISO8601 datedate --iso-8601=ns # Print the ISO8601 date and timedate -s "02 DEC 2020 12:02:02" # Manually change date and timedpkg-reconfigure tzdata # Change date/timezoneuptime # Print how long the system has been runningtime tree # Print amount of time to tree takes to execute```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Scheduled Tasks```pre * * * * *Minute, Hour, Day of month, Month, Day of the week``````bashcrontab -l # List cron tabcrontab -e # Edit cron tab in Vimcrontab /path/crontab # Load cron tab from a filecrontab -l > /path/crontab # Save cron tab to a file* * * * * foo # Run foo every minute*/15 * * * * foo # Run foo every 15 minutes0 * * * * foo # Run foo every hour15 6 * * * foo # Run foo daily at 6:15 AM44 4 * * 5 foo # Run foo every Friday at 4:44 AM0 0 1 * * foo # Run foo at midnight on the first of the month0 0 1 1 * foo # Run foo at midnight on the first of the yearat -l # List scheduled tasksat -c 1 # Show task with ID 1at -r 1 # Remove task with ID 1at now + 2 minutes # Create a task in Vim to execute in 2 minutesat 12:34 PM next month # Create a task in Vim to execute at 12:34 PM next monthat tomorrow # Create a task in Vim to execute tomorrow```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## User Management```bashadduser username # To add a new userpasswd -l|--lock username # To change the password of a useruserdel username # To remove useruserdel -r|--remove username # To remove user with home directory and mail spoolusermod -a|--append -G|--groups GROUPNAME USERNAME # To add a user to a groupdeluser USER GROUPNAME # To remove a user from a grouplast # Shows information of all the users logged inlast username # Gives information of a particular user```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## HTTP Requests```bashcurl https://example.com # Return response bodycurl -i|--include https://example.com # Include status code and HTTP headerscurl -L|--location https://example.com # Follow redirectscurl -O|--remote-name foo.txt https://example.com # Output to a text filecurl -H|--header "User-Agent: Foo" https://example.com # Add a HTTP headercurl -X|--request POST -H "Content-Type: application/json" -d|--data '{"foo":"bar"}' https://example.com # POST JSONcurl -X POST -H --data-urlencode foo="bar" http://example.com # POST URL Form Encodedwget https://example.com/file.txt # Download a file to the current directorywget -O|--output-document foo.txt https://example.com/file.txt # Output to a file with the specified name```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Network Troubleshooting```bashping example.com # Send multiple ping requests using the ICMP protocolping -c 10 -i 5 example.com # Make 10 attempts, 5 seconds apartip addr # List IP addresses on the systemip route show # Show IP addresses to routercurl ifconfig.me # Obtain external IP addressnetstat -i|--interfaces # List all network interfaces and in/out usagenetstat -l|--listening # List all open portstraceroute example.com # List all servers the network traffic goes throughmtr -w|--report-wide example.com # Continually list all servers the network traffic goes throughmtr -r|--report -w|--report-wide -c|--report-cycles 100 example.com # Output a report that lists network traffic 100 timesnmap 0.0.0.0 # Scan for the 1000 most common open ports on localhostnmap 0.0.0.0 -p1-65535 # Scan for open ports on localhost between 1 and 65535nmap 192.168.4.3 # Scan for the 1000 most common open ports on a remote IP addressnmap -sP 192.168.1.1/24 # Discover all machines on the network by ping'ing them```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## DNS```bashdig example.com # Show query information of domain A recordsdig -4 example.com # Show IPv4 A recordsdig -6 example.com # Show IPv6 AAA recordsdig example.com @nameserver # Show query of a specific nameserverdig example.com -p 123 # Show query of a specific port numbercat /etc/resolv.conf # Nameservers filecat /etc/systemd/resolved.conf # DNS resolver config file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Hardware```bashlsusb # List USB deviceslspci # List PCI hardwarelshw # List all hardware```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## System Information```uname -s # Print kernel nameuname -r # Print kernel releaseuname -m # Print Architectureuname -o # Print Operating System```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Terminal MultiplexersStart multiple terminal sessions. Active sessions persist reboots. `tmux` is more modern than `screen`.```bashtmux # Start a new session (CTRL-b + d to detach)tmux ls # List all sessionstmux attach -t 0 # Reattach to a sessionscreen # Start a new session (CTRL-a + d to detach)screen -ls # List all sessionsscreen -R 31166 # Reattach to a sessionexit # Exit a session```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Secure Shell Protocol (SSH)```bashssh hostname # Connect to hostname using your current user name over the default SSH port 22ssh -i foo.pem hostname # Connect to hostname using the identity filessh user@hostname # Connect to hostname using the user over the default SSH port 22ssh user@hostname -p 8765 # Connect to hostname using the user over a custom portssh ssh://user@hostname:8765 # Connect to hostname using the user over a custom port```Set default user and port in `~/.ssh/config`, so you can just enter the name next time:```bash$ cat ~/.ssh/configHost name User foo Hostname 127.0.0.1 Port 8765$ ssh name```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Secure Copy```bashscp foo.txt ubuntu@hostname:/home/ubuntu # Copy foo.txt into the specified remote directoryscp ubuntu@hostname:/home/ubuntu/foo.txt /C:\Users\Admin # Copy foo.txt from the specified remote directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Bash Profile- bash - `.bashrc`- zsh - `.zshrc````bash# Always run ls after cdfunction cd { builtin cd "$@" && ls}# Prompt user before overwriting any filesalias cp='cp --interactive'alias mv='mv --interactive'alias rm='rm --interactive'# Always show disk usage in a human readable formatalias df='df -h'alias du='du -h'```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Bash Script### Variables```bash#!/bin/bashfoo=123 # Initialize variable foo with 123declare -i foo=123 # Initialize an integer foo with 123declare -r foo=123 # Initialize readonly variable foo with 123echo $foo # Print variable fooecho ${foo}_'bar' # Print variable foo followed by _barecho ${foo:-'default'} # Print variable foo if it exists otherwise print defaultexport foo # Make foo available to child processesunset foo # Make foo unavailable to child processes and current session```### Environment Variables```bash#!/bin/bashset # List all environment variablesecho $PATH # Print PATH environment variableexport FOO=Bar # Set an environment variable```### Functions```bash#!/bin/bashgreet() { local world="World" echo "$1 $world" return "$1 $world"}greet "Hello"greeting=$(greet "Hello")```### Exit Codes```bash#!/bin/bashexit 0 # Exit the script successfullyexit 1 # Exit the script unsuccessfullyecho $? # Print the last exit code```### Conditional Statements#### Boolean Operators- `$foo` - Is true- `!$foo` - Is false#### Numeric Operators- `-eq` - Equals- `-ne` - Not equals- `-gt` - Greater than- `-ge` - Greater than or equal to- `-lt` - Less than- `-le` - Less than or equal to- `-e` foo.txt - Check file exists- `-z` foo - Check if variable exists#### String Operators- `=` - Equals- `==` - Equals- `-z` - Is null- `-n` - Is not null- `<` - Is less than in ASCII alphabetical order- `>` - Is greater than in ASCII alphabetical order#### If Statements```bash#!/bin/bash[[if [[$foo = 'bar']]; then echo 'one'elif [[$foo = 'bar']] || [[$foo = 'baz']]; then echo 'two'elif [[$foo = 'ban']] && [[$USER = 'bat']]; then echo 'three'else echo 'four'fi]]```#### Inline If Statements```bash#!/bin/bash[[ $USER = 'rehan' ]] && echo 'yes' || echo 'no'```#### While Loops```bash#!/bin/bash[declare -i countercounter=10while [$counter -gt 2]; do echo The counter is $counter counter=counter-1done]```#### For Loops```bash#!/bin/bashfor i in {0..10..2} do echo "Index: $i" donefor filename in file1 file2 file3 do echo "Content: " >> $filename donefor filename in *; do echo "Content: " >> $filename done```#### Case Statements```bash#!/bin/bashecho "What's the weather like tomorrow?"read weathercase $weather in sunny | warm ) echo "Nice weather: " $weather ;; cloudy | cool ) echo "Not bad weather: " $weather ;; rainy | cold ) echo "Terrible weather: " $weather ;; * ) echo "Don't understand" ;;esac```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents) Special characters 🔣 Char. Description ~ Home directory [tilde]. The current user's home directory location. - Previous directory [dash]. Go back to previous directories. / Filename path separator [forward slash]. Separates the components of a filename. \ Escape [backslash]. A quoting mechanism for single characters. \X escapes the character X. It preserves the literal value of the next character that follows, with the exception of newline. │ Pipe. It passes the output (stdout) of a previous command to the input (stdin) of the next one, or to the shell. This is a method of chaining commands together. || The OR logical operator causes a return of 0 (success) if either of the linked test conditions is true. && The AND logical operator causes a return of 0 (success) only if both the linked test conditions are true. >, >>, < Redirect a command's output or input into a file. >| Force redirection (even if the noclobber option is set). This will forcibly overwrite an existing file. & Run job in background[and]. A command followed by an & will run in the background. # Comment [number sign]. Lines in files beginning with a # (with the exception of #!) are comments and will not be executed. "" Double quotes protects the text inside them from being split into multiple words or arguments, yet allow substitutions to occur, meaning most other special characters is usually prevented. ' ' Single quotes protects the text inside them so that it has a literal meaning. This is a stronger form of quoting than " ". " " Whitespace. This is a tab, newline, vertical tab, form feed, carriage return, or space. Bash uses whitespace to determine where words begin and end. ; Command separator [semicolon]. Used to separate multiple commands that are on the same line. : Null command [colon]. This is the shell equivalent of a "NOP" (no op, a do-nothing operation). It may be considered a synonym for the shell builtin true. ! Reverse (or negate) [exclamation]. The ! operator inverts the exit status of the command to which it is applied. It also inverts the meaning of a test operator. * Wild card [asterisk]. The * character serves as a "wild card" for filename expansion in globbing . By itself, it matches every filename in a given directory. ? Wild card[qestion mark]. The ? character serves as a single-character "wild card" for filename expansion in globbing, as well as representing one character in an extended regular expression. { } Inline group [curly brackets]. Commands inside the curly braces are treated as if they were one command. It is convenient to use these when Bash syntax requires only one command and a function doesn't feel warranted. ( ) Subshell group [bracket].Commands within are executed in a subshell (a new process) Used much like a sandbox, if a command causes side effects (like changing variables), it will have no effect on the current shell. [ ] Test expression between [ ]. Is part of the shell builtin test. [[ ]] Test expression between [[ ]]. More flexible than the single-bracket [ ] test. (( )) Integer expansion. Expand and evaluate integer expression. ;; Terminator in a case option [double semicolon]. ,, , Lowercase conversion in parameter substitution. ^, ^^ Uppercase conversion in parameter substitution. Keyboard controls ⌨️ | Key | Function || :--: | :-- || Ctrl+a | Moves cursor to beginning of text in line || Ctrl+e | Moves cursor to end of text in line || Ctrl+b | Moves cursor backward one character position || Ctrl+f | Moves cursor forward one character position || Ctrl+p | Fetch previous command from history buffer || Ctrl+n | Fetch next command from history buffer || Ctrl+r | Reverse search commands in history buffer || Ctrl+u | Erase a line of input from cursor right to left of line || Ctrl+k | Erase a line of input from cursor left to right of line || Ctrl+w | Erases backwards to first non-alphanumeric character or space || Ctrl+y | Fetch back command previously erased || Ctrl+t | Reverses the position of the character the cursor is on with the previous character || Ctrl+z | Pauses a foreground job || Ctrl+c | Break/Terminate a foreground job || Ctrl+o | Accept the current line for execution and fetch the next command || Ctrl+l | Clear screen (command line needs to be empty) || Ctrl+s | Suspend || Ctrl+q | Resume || Ctrl+d | Log out from a shell (similar to exit) | Online Cheat Sheet :feelsgood: for quick references of commands and codes cheat.sh Terminal: ```bashcurl cht.sh/keyword or curl cheat.sh/keyword``` Browser: https://cht.sh/ keyword or https://cheat.sh/ keyword Offline usage Install cheat script manually: ```bash Install globally(all users): curl -s https://cht.sh/:cht.sh | sudo tee /usr/local/bin/cht.sh && sudo chmod +x /usr/local/bin/cht.sh Run script: cht.sh ``` To restore the repository download the bundle wget https://archive.org/download/github.com-trinib-Linux-Bash-Commands_-_2022-11-08_01-19-56/trinib-Linux-Bash-Commands_-_2022-11-08_01-19-56.bundle and run: git clone trinib-Linux-Bash-Commands_-_2022-11-08_01-19-56.bundle Source: https://github.com/trinib/Linux-Bash-Commands Uploader: trinib Upload date: 2022-11-08

:godmode: Ultimate list of Linux bash commands # Ultimate list of Linux bash commands_Bash is the [Unix](https://www.google.com/search?q=What+is+UNIX+explain%3F&client=firefox-b-d&sxsrf=ALiCzsZmYtgn9ctD5vHAqgVFkM5tZ514pw%3A1667926333803&ei=PYlqY6XIMNmNwbkPqeK3qAo&ved=0ahUKEwjl2ozlhZ_7AhXZRjABHSnxDaUQ4dUDCA4&uact=5&oq=What+is+UNIX+explain%3F&gs_lcp=Cgxnd3Mtd2l6LXNlcnAQAzIFCAAQgAQyBQgAEIAEMgUIABCABDIGCAAQFhAeMgYIABAWEB4yBggAEBYQHjIFCAAQhgMyBQgAEIYDMgUIABCGAzIFCAAQhgM6CggAEEcQ1gQQsAM6BwgAELADEENKBAhNGAFKBAhBGABKBAhGGABQnAFYnAFgvwNoAXABeACAAa0BiAGtAZIBAzAuMZgBAKABAqABAcgBCsABAQ&sclient=gws-wiz-serp) command-line interface (CLI). Also called the terminal, the command line, or the shell. It's a command language that allows us to work with files on our computers in a way that's far more efficient and powerful than using a GUI (graphical user interface)_ A to Z command list 📚 > **Note** > Use `Ctrl+f` to search in browsers🔎 Table #### │ [A](#-a) │ [B](#-b) │ [C](#-c) │ [D](#-d) │ [E](#-e) │ [F](#-f) │ [G](#-g) │ [H](#-h) │ [I](#-i) │ [J](#-j) │ [K](#-k) │ [L](#-l) │ [M](#-m) │ [N](#-n) │ [O](#-o) │ [P](#-p) │ [Q](#-q) │ [R](#-r) │ [S](#-s) │ [T](#-t) │ [U](#-u) │ [V](#-v) │ [W](#-w) │ [X](#-x) │ [Y](#-y) │ [Z](#-z) │ A Command Description accept Accept or Reject jobs to a destination, such as a printer. access Check a user’s RWX permission for a file. aclocal GNU autoconf tool. aconnect ALSA sequencer connection manager. acpi Show information about the Advanced Configuration and Power Interface. acpi_available Check if ACPI functionality exists on the system. acpid Informs user-space programs about ACPI events. addr2line Used to convert addresses into file names and line numbers. addresses Formats for internet mail addresses. agetty An alternative Linux Getty. alias Create an alias for Linux commands. alsactl Access advanced controls for ALSA soundcard driver. amidi Perform read/write operation for ALSA RawMIDI ports. amixer Access CLI-based mixer for ALSA soundcard driver. anacron Used to run commands periodically. aplay Sound recorder and player for CLI. aplaymidi CLI utility used to play MIDI files. apm Show Advanced Power Management (APM) hardware info on older systems. apmd Used to handle events reported by APM BIOS drivers. apropos Shows the list of all man pages containing a specific keyword. apt Advanced Package Tool, a package management system for Debian and derivatives. apt-get Command-line utility to install/remove/update packages based on APT system. aptitude Another utility to add/remove/upgrade packages based on the APT system. ar A utility to create/modify/extract from archives. arch Display print machine hardware name. arecord Just like aplay, it’s a sound recorder and player for ALSA soundcard driver. arecordmidi Record standard MIDI files. arp Used to make changes to the system’s ARP cache. as A portable GNU assembler. aspell An interactive spell checker utility. at Used to schedule command execution at specified date & time, reading commands from an input file. atd Used to execute jobs queued by the at command. atq List a user’s pending jobs for the at command. atrm Delete jobs queued by the at command. audiosend Used to send an audio recording as an email. aumix An audio mixer utility. autoconf Generate configuration scripts from a TEMPLATE-FILE and send the output to standard output. autoheader Create a template header for configure. automake Creates GNU standards-compliant Makefiles from template files. autoreconf Update generated configuration files. autoscan Generate a preliminary configure.in file. autoupdate Update a configure.in file to newer autoconf. awk Used to find and replace text in a file(s). [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) B Command Description badblocks Search a disk partition for bad sectors. banner Used to print characters as a poster. basename Used to display filenames with directory or suffix. bash GNU Bourne-Again Shell. batch Used to run commands entered on a standard input. bc Access the GNU bc calculator utility. bg Send processes to the background. biff Notify about incoming mail and sender’s name on a system running comsat server. bind Used to attach a name to a socket. bison A GNU parser generator, compatible with yacc. break Used to exit from a loop (eg: for, while, select). builtin Used to run shell builtin commands, make custom functions for commands extending their functionality. bzcmp Used to call the cmp program forbzip2 compressed files. bzdiff Used to call the diff program for bzip2 compressed files. bzgrep Used to call grep for bzip2 compressed files. bzip2 A block-sorting file compressor used to shrink given files. bzless Used to apply ‘less’ (show info one page at a time) to bzip2 compressed files. bzmore Used to apply ‘more’ (an inferior version of less) to bzip2 compressed files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) C Command Description cal Show calendar. cardctl Used to control PCMCIA sockets and select configuration schemes. cardmgr Keeps an eye on the added/removes sockets for PCMCIA devices. case Execute a command conditionally by matching a pattern. cat Used to concatenate files and print them on the screen. cc GNU C and C++ compiler. cd Used to change directory. cdda2wav Used to rip a CD-ROM and make WAV file. cdparanoia Record audio from CD more reliably using data-verification algorithms. cdrdao Used to write all the content specified to a file to a CD all at once. cdrecord Used to record data or audio compact discs. cfdisk Show or change the disk partition table. chage Used to change user password information. chattr Used to change file attributes. chdir Used to change active working directory. chfn Used to change real user name and information. chgrp Used to change group ownership for file. chkconfig Manage execution of runlevel services. chmod Change access permission for a file(s). chown Change the owner or group for a file. chpasswd Update password in a batch. chroot Run a command with root directory. chrt Alter process attributed in real-time. chsh Switch login shell. chvt Change foreground virtual terminal. cksum Perform a CRC checksum for files. clear Used to clear the terminal window. cmp Compare two files (byte by byte). col Filter reverse (and half-reverse) line feeds from the input. colcrt Filter nroff output for CRT previewing. colrm Remove columns from the lines of a file. column A utility that formats its input into columns. comm Used to compare two sorted files line by line. command Used to execute a command with arguments ignoring shell function named command. compress Used to compress one or more file(s) and replacing the originals ones. continue Resume the next iteration of a loop. cp Copy contents of one file to another. cpio Copy files from and to archives. cpp GNU C language processor. cron A daemon to execute scheduled commands. crond Same work as cron. crontab Manage crontab files (containing schedules commands) for users. csplit Split a file into sections on the basis of context lines. ctags Make a list of functions and macro names defined in a programming source file. cupsd A scheduler for CUPS. curl Used to transfer data from or to a server using supported protocols. cut Used to remove sections from each line of a file(s). cvs Concurrent Versions System. Used to track file versions, allow storage/retrieval of previous versions, and enables multiple users to work on the same file. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) D Command Description date Show system date and time. dc Desk calculator utility. dd Used to convert and copy a file, create disk clone, write disk headers, etc. ddrescue Used to recover data from a crashed partition. deallocvt Deallocates kernel memory for unused virtual consoles. debugfs File system debugger for ext2/ext3/ext4 declare Used to declare variables and assign attributes. depmod Generate modules.dep and map files. devdump Interactively displays the contents of device or file system ISO. df Show disk usage. diff Used to compare files line by line. diff3 Compare three files line by line. dig Domain Information Groper, a DNS lookup utility. dir List the contents of a directory. dircolors Set colors for ‘ls’ by altering the LS_COLORS environment variable. dirname Display pathname after removing the last slash and characters thereafter. dirs Show the list of remembered directories. disable Restrict access to a printer. dlpsh Interactive Desktop Link Protocol (DLP) shell for PalmOS. dmesg Examine and control the kernel ring buffer. dnsdomainname Show the DNS domain name of the system. dnssec-keygen Generate encrypted Secure DNS keys for a given domain name. dnssec-makekeyset Produce domain key set from one or more DNS security keys generated by dnssec-keygen. dnssec-signkey Sign a secure DNS keyset with key signatures specified in the list of key-identifiers. dnssec-signzone Sign a secure DNS zonefile with the signatures in the specified list of key-identifiers. doexec Used to run an executable with an arbitrary argv list provided. domainname Show or set the name of current NIS (Network Information Services) domain. dosfsck Check and repair MS-DOS file systems. du Show disk usage summary for a file(s). dump Backup utility for ext2/ext3 file systems. dumpe2fs Dump ext2/ext3/ext4 file systems. dumpkeys Show information about the keyboard driver’s current translation tables. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) E Command Description e2fsck Used to check ext2/ext3/ext4 file systems. e2image Store important ext2/ext3/ext4 filesystem metadata to a file. e2label Show or change the label on an ext2/ext3/ext4 filesystem. echo Send input string(s) to standard output i.e. display text on the screen. ed GNU Ed – a line-oriented text editor. edquota Used to edit filesystem quotas using a text editor, such as vi. egrep Search and display text matching a pattern. eject Eject removable media. elvtune Used to set latency in the elevator algorithm used to schedule I/O activities for specified block devices. emacs Emacs text editor command line utility. enable Used to enable/disable shell builtin commands. env Run a command in a modified environment. Show/set/delete environment variables. envsubst Substitute environment variable values in shell format strings. esd Start the Enlightenment Sound Daemon (EsounD or esd). Enables multiple applications to access the same audio device simultaneously. esd-config Manage EsounD configuration. esdcat Use EsounD to send audio data from a specified file. esdctl EsounD control program. esddsp Used to reroute non-esd audio data to esd and control all the audio using esd. esdmon Used to copy the sound being sent to a device. Also, send it to a secondary device. esdplay Use EsounD system to play a file. esdrec Use EsounD to record audio to a specified file. esdsample Sample audio using esd. etags Used to create a list of functions and macros from a programming source file. These etags are used by emacs. For vi, use ctags. ethtool Used to query and control network driver and hardware settings. eval Used to evaluate multiple commands or arguments are once. ex Interactive command exec An interactive line-based text editor. exit Exit from the terminal. expand Convert tabs into spaces in a given file and show the output. expect An extension to the Tcl script, it’s used to automate interaction with other applications based on their expected output. export Used to set an environment variable. expr Evaluate expressions and display them on standard output. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) F Command Description factor Display prime factors of specified integer numbers. false Do nothing, unsuccessfully. Exit with a status code indicating failure. fc-cache Make font information cache after scanning the directories. fc-list Show the list of available fonts. fdformat Do a low-level format on a floppy disk. fdisk Make changes to the disk partition table. fetchmail Fetch mail from mail servers and forward it to the local mail delivery system. fg Used to send a job to the foreground. fgconsole Display the number of the current virtual console. fgrep Display lines from a file(s) that match a specified string. A variant of grep. file Determine file type for a file. find Do a file search in a directory hierarchy. finger Display user data including the information listed in .plan and .project in each user’s home directory. fingerd Provides a network interface for the finger program. flex Generate programs that perform pattern-matching on text. fmt Used to convert text to a specified width by filling lines and removing new lines, displaying the output. fold Wrap input line to fit in a specified width. for Expand words and run commands for each one in the resultant list. formail Used to filter standard input into mailbox format. format Used to format disks. free Show free and used system memory. fsck Check and repair a Linux file system ftp File transfer protocol user interface. ftpd FTP server process. function Used to define function macros. fuser Find and kill a process accessing a file. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) G Command Description g++ Run the g++ compiler. gawk Used for pattern scanning and language processing. A GNU implementation of AWK language. gcc A C and C++ compiler by GNU. gdb A utility to debug programs and know about where it crashes. getent Shows entries from Name Service Switch Libraries for specified keys. getkeycodes Displays the kernel scancode-to-keycode mapping table. getopts A utility to parse positional parameters. gpasswd Allows an administrator to change group passwords. gpg Enables encryption and signing services as per the OpenPGP standard. gpgsplit Used to split an OpenPGP message into packets. gpgv Used to verify OpenPGP signatures. gpm It enables cut and paste functionality and a mouse server for the Linux console. gprof Shows call graph profile data. grep Searches input files for a given pattern and displays the relevant lines. groff Serves as the front-end of the groff document formatting system. groffer Displays groff files and man pages. groupadd Used to add a new user group. groupdel Used to remove a user group. groupmod Used to modify a group definition. groups Showthe group(s) to which a user belongs. grpck Verifies the integrity of group files. grpconv Creates agshadow file from a group or an already existing gshadow. gs Invokes Ghostscript, and interpreter and previewer for Adobe’s PostScript and PDF languages. gunzip A utility to compress/expand files. gzexe Used compress executable files in place and have them automatically uncompress and run at a later stage. gzip A utility to compress/expand files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) H Command Description halt Command used to half the machine. hash Shows the path for the commands executed in the shell. hdparm Show/configure parameters for SATA/IDE devices. head Shows first 10 lines from each specified file. help Display’s help for a built-in command. hexdump Shows specified file output in hexadecimal, octal, decimal, or ASCII format. history Shows the command history. host A utility to perform DNS lookups. hostid Shows host’s numeric ID in hexadecimal format. hostname Display/set the hostname of the system. htdigest Manage the user authentication file used by the Apache web server. htop An interactive process viewer for the command line. hwclock Show or configure the system’s hardware clock. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) I Command Description iconv Convert text file from one encoding to another. id Show user and group information for a specified user. if Execute a command conditionally. ifconfig Used to configure network interfaces. ifdown Stops a network interface. ifup Starts a network interface. imapd An IMAP (Interactive Mail Access Protocol) server daemon. import Capture an X server screen and saves it as an image. inetd Extended internet services daemon, it starts the programs that provide internet services. info Used to read the documentation in Info format. init Systemd system and service manager. insmod A program that inserts a module into the Linux kernel. install Used to copy files to specified locations and set attributions during the install process. iostat Shows statistics for CPU, I/O devices, partitions, network filesystems. ip Display/manipulate routing, devices, policy, routing and tunnels. ipcrm Used to remove System V interprocess communication (IPC) objects and associated data structures. ipcs Show information on IPC facilities for which calling process has read access. iptables Administration tool for IPv4 packet filtering and NAT. iptables-restore Used to restore IP tables from data specified in the input or a file. iptables-save Used to dump IP table contents to standard output. isodump A utility that shows the content iso9660 images to verify the integrity of directory contents. isoinfo A utility to perform directory like listings of iso9660 images. isosize Show the length of an iso9660 filesystem contained in a specified file. isovfy Verifies the integrity of an iso9660 image. ispell A CLI-based spell-check utility. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) J Command Description jobs Show the list of active jobs and their status. join For each pair of input lines, join them using a command field and display on standard output. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) K Command Description kbd_mode Set a keyboard mode. Without arguments, shows the current keyboard mode. kbdrate Reset keyboard repeat rate and delay time. kill Send a kill (termination) signal to one more processes. killall Kills a process(es) running a specified command. killall5 A SystemV killall command. Kills all the processes excluding the ones which it depends on. klogd Control and prioritize the kernel messages to be displayed on the console, and log them through syslogd. kudzu Used to detect new and enhanced hardware by comparing it with existing database. Only for RHEL and derivatives. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) L Command Description last Shows a list of recent logins on the system by fetching data from /var/log/wtmp file. lastb Shows the list of bad login attempts by fetching data from /var/log/btmp file. lastlog Displays information about the most recent login of all users or a specified user. ld The Unix linker, it combines archives and object files. It then puts them into one output file, resolving external references. ldconfig Configure dynamic linker run-time bindings. ldd Shows shared object dependencies. less Displays contents of a fileone page at a time. It’s advanced than more command. lesskey Used to specify key bindings for less command. let Used to perform integer artithmetic on shell variables. lftp An FTP utility with extra features. lftpget Uses lftop to retrieve HTTP, FTP, and other protocol URLs supported by lftp. link Create links between two files. Similar to ln command. ln Create links between files. Links can be hard (two names for the same file) or soft (a shortcut of the first file). loadkeys Load keyboard translation tables. local Used to create function variables. locale Shows information about current or all locales. locate Used to find files by their name. lockfile Create semaphore file(s) which can be used to limit access to a file. logger Make entries in the system log. login Create a new session on the system. logname Shows the login name of the current user. logout Performs the logout operation by making changes to the utmp and wtmp files. logrotate Used for automatic rotation, compression, removal, and mailing of system log files. look Shows any lines in a file containing a given string in the beginning. losetup Set up and control loop devices. lpadmin Used to configure printer and class queues provided by CUPS (Common UNIX Printing System). lpc Line printer control program, it provides limited control over CUPS printer and class queues. lpinfo Shows the list of available devices and drivers known to the CUPS server. lpmove Move on or more printing jobs to a new destination. lpq Shows current print queue status for a specified printer. lpr Used to submit files for printing. lprint Used to print a file. lprintd Used to abort a print job. lprintq List the print queue. lprm Cancel print jobs. lpstat Displays status information about current classes, jobs, and printers. ls Shows the list of files in the current directory. lsattr Shows file attributes on a Linux ext2 file system. lsblk Lists information about all available or the specified block devices. lsmod Show the status of modules in the Linux kernel. lsof List open files. lspci List all PCI devices. lsusb List USB devices. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) M Command Description m4 Macro processor. mail Utility to compose, receive, send, forward, and reply to emails. mailq Shows to list all emails queued for delivery (sendmail queue). mailstats Shows current mail statistics. mailto Used to send mail with multimedia content in MIME format. make Utility to maintain groups of programs, recompile them if needed. makedbm Creates an NIS (Network Information Services) database map. makemap Creates database maps used by the keyed map lookups in sendmail. man Shows manual pages for Linux commands. manpath Determine search path for manual pages. mattrib Used to change MS-DOS file attribute flags. mbadblocks Checks MD-DOS filesystems for bad blocks. mcat Dump raw disk image. mcd Used to change MS-DOS directory. mcopy Used to copy MS-DOS files from or to Unix. md5sum Used to check MD5 checksum for a file. mdel, mdeltree Used to delete MS-DOS file. mdeltree recursively deletes MS-DOS directory and its contents. mdir Used to display an MS-DOS directory. mdu Used to display the amount of space occupied by an MS-DOS directory. merge Three-way file merge. Includes all changes from file2 and file3 to file1. mesg Allow/disallow osends to sedn write messages to your terminal. metamail For sending and showing rich text or multimedia email using MIME typing metadata. metasend An interface for sending non-text mail. mformat Used to add an MS-DOS filesystem to a low-level formatted floppy disk. mimencode Translate to/from MIME multimedia mail encoding formats. minfo Display parameters of an MS-DOS filesystem. mkdir Used to create directories. mkdosfs Used to create an MS-DOS filesystem under Linux. mke2fs Used create an ext2/ext3/ext4 filesystem. mkfifo Used to create named pipes (FIFOs) with the given names. mkfs Used to build a Linux filesystem on a hard disk partition. mkfs.ext3 Same as mke2fs, create an ext3 Linux filesystem. mkisofs Used to create an ISO9660/JOLIET/HFS hybrid filesystem. mklost+found Create a lost+found directory on a mounted ext2 filesystem. mkmanifest Makes alist of file names and their DOS 8.3 equivalent. mknod Create a FIFO, block (buffered) special file, character (unbuffered) special file with the specified name. mkraid Used to setup RAID device arrays. mkswap Set up a Linux swap area. mktemp Create a temporary file or directory. mlabel Make an MD-DOS volume label. mmd Make an MS-DOS subdirectory. mmount Mount an MS-DOS disk. mmove Move or rename an MS-DOS file or subdirectory. mmv Mass move and rename files. modinfo Show information about a Linux kernel module. modprobe Add or remove modules from the Linux kernel. more Display content of a file page-by-page. most Browse or page through a text file. mount Mount a filesystem. mountd NFS mount daemon. mpartition Partition an MS-DOS disk. mpg123 Command-line mp3 player. mpg321 Similar to mpg123. mrd Remove an MS-DOS subdirectory. mren Rename an existing MS-DOS file. mshowfat Show FTA clusters allocated to a file. mt Control magnetic tape drive operation. mtools Utilities to access MS-DOS disks. mtoolstest Tests and displays the mtools configuration files. mtr A network diagnostic tool. mtype Display contents of an MS-DOS file. mv Move/rename files or directories. mzip Change protection mode and eject disk on Zip/Jaz drive. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) N Command Description named Internet domain name server. namei Follow a pathname until a terminal point is found. nameif Name network interfaces based on MAC addresses. nc Netcat utility. Arbitrary TCP and UDP connections and listens. netstat Show network information. newaliases Rebuilds mail alias database. newgrp Log-in to a new group. newusers Update/create new users in batch. nfsd Special filesystem for controlling Linux NFS server. nfsstat List NFS statistics. nice Run a program with modified scheduling priority. nl Show numbered line while displaying the contents of a file. nm List symbols from object files. nohup Run a command immune to hangups. notify-send A program to send desktop notifications. nslookup Used performs DNS queries. Read this article for more info. nsupdate Dynamic DNS update utility. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) O Command Description objcopy Copy and translate object files. objdump Display information from object files. od Dump files in octal and other formats. op Operator access, allows system administrators to grant users access to certain root operations that require superuser privileges. open Open a file using its default application. openvt Start a program on a new virtual terminal (VT). [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) P Command Description passwd Change user password. paste Merge lines of files. Write to standard output, TAB-separated lines consisting of sequentially corresponding lines from each file. patch Apply a patchfile (containing differences listing by diff program) to an original file. pathchk Check if file names are valid or portable. perl Perl 5 language interpreter. pgrep List process IDs matching the specified criteria among all the running processes. pidof Find process ID of a running program. ping Send ICMP ECHO_REQUEST to network hosts. pinky Lightweight finger. pkill Send kill signal to processes based on name and other attributes. pmap Report memory map of a process. popd Removes directory on the head of the directory stack and takes you to the new directory on the head. portmap Converts RPC program numbers to IP port numbers. poweroff Shuts down the machine. pppd Point-to-point protocol daemon. pr Convert (column or paginate) text files for printing. praliases Prints the current system mail aliases. printcap Printer capability database. printenv Show values of all or specified environment variables. printf Show arguments formatted according to a specified format. ps Report a snapshot of the current processes. ptx Produce a permuted index of file contents. pushd Appends a given directory name to the head of the stack and then cd to the given directory. pv Monitor progress of data through a pipe. pwck Verify integrity of password files. pwconv Creates shadow from passwd and an optionally existing shadow. pwd Show current directory. python [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Q Command Description quota Shows disk usage, and space limits for a user or group. Without arguments, only shows user quotas. quotacheck Used to scan a file system for disk usage. quotactl Make changes to disk quotas. quotaoff Enable enforcement of filesystem quotas. quotaon Disable enforcement of filesystem quotas. quotastats Shows the report of quota system statistics gathered from the kernel. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) R Command Description raidstart Start/stop RAID devices. ram RAM disk device used to access the RAM disk in raw mode. ramsize Show usage information for the RAM disk. ranlib Generate index to the contents of an archive and store it in the archive. rar Create and manage RAR file in Linux. rarpd Respond to Reverse Address Resolution Protocol (RARP) requests. rcp Remote copy command to copy files between remote computers. rdate Set system date and time by fetching information from a remote machine. rdev Set or query RAM disk size, image root device, or video mode. rdist Remote file distribution client, maintains identical file copies over multiple hosts. rdistd Start the rdist server. read Read from a file descriptor. readarray Read lines from a file into an array variable. readcd Read/write compact disks. readelf Shows information about ELF (Executable and Linkable format) files. readlink Display value of a symbolic link or canonical file name. readonly Mark functions and variables as read-only. reboot Restart the machine. reject Accept/reject print jobs sent to a specified destination. remsync Synchronize remote files over email. rename Rename one or more files. renice Change priority of active processes. repquota Report disk usage and quotas for a specified filesystem. reset Reinitialize the terminal. resize2fs Used to resize ext2/ext3/ext4 file systems. restore Restore files from a backup created using dump. return Exit a shell function. rev Show contents of a file, reversing the order of characters in every line. rexec Remote execution client for exec server. rexecd Remote execution server. richtext View “richtext” on an ACSII terminal. rlogin Used to connect a local host system with a remote host. rlogind Acts as the server for rlogin.It facilitates remote login, and authentication based on privileged port numbers from trusted hosts. rm Removes specified files and directories (not by default). rmail Handle remote mail received via uucp. rmdir Used to remove empty directories. rmmod A program to remove modules from Linux kernel. rndc Name server control utility. Send command to a BIND DNS server over a TCP connection. rootflags Show/set flags for the kernel image. route Show/change IP routing table. routed A daemon, invoked at boot time, to manage internet routing tables. rpcgen An RPC protocol compiler. Parse a file written in the RPC language. rpcinfo Shows RPC information. Makes an RPC call to an RPC server and reports the findings. rpm A package manager for Linux distributions. Originally developed for RedHat Linux. rsh Remote shell. Connects to a specified host and executes commands. rshd A daemon that acts as a server for rsh and rcp commands. rsync A versitile to for copying files remotely and locally. runlevel Shows previous and current SysV runlevel. rup Remote status display. Shows current system status for all or specified hosts on the local network. ruptime Shows uptime and login details of the machines on the local network. rusers Shows the list of the users logged-in to the host or on all machines on the local network. rusersd The rsuerd daemon acts as a server that responds to the queries from rsuers command. rwall Sends messages to all users on the local network. rwho Reports who is logged-in to the hosts on the local network. rwhod Acts as a server for rwho and ruptime commands. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) S Command Description sane-find-scanner Find SCSI and USB scanner and determine their device files. scanadf Retrieve multiple images from a scanner equipped with an automatic document feeder (ADF). scanimage Read images from image acquisition devices (scanner or camera) and display on standard output in PNM (Portable aNyMap) format. scp Copy files between hosts on a network securely using SSH. screen A window manager that enables multiple pseudo-terminals with the help of ANSI/VT100 terminal emulation. script Used to make a typescript of everything displayed on the screen during a terminal session. sdiff Shows two files side-by-side and highlights the differences. sed Stream editor for filtering and transforming text (from a file or a pipe input). select Synchronous I/O multiplexing. sendmail It’s a mail router or an MTA (Mail Transfer Agent). sendmail support can send a mail to one or more recipients using necessary protocols. sensors Shows the current readings of all sensor chips. seq Displays an incremental sequence of numbers from first to last. set Used to manipulate shell variables and functions. setfdprm Sets floppy disk parameters as provided by the user. setkeycodes Load kernel scancode-to-keycode mapping table entries. setleds Show/change LED light settings of the keyboard. setmetamode Define keyboard meta key handling. Without arguments, shows current meta key mode. setquota Set disk quotas for users and groups. setsid Run a program in a new session. setterm Set terminal attributes. sftp Secure File Transfer program. sh Command interpreter (shell) utility. sha1sum Compute and check 160-bit SHA1 checksum to verify file integrity. shift Shift positional parameters. shopt Shell options. showkey Examines codes sent by the keyboard displays them in printable form. showmount Shows information about NFS server mount on the host. shred Overwrite a file to hide its content (optionally delete it), making it harder to recover it. shutdown Power-off the machine. size Lists section size and the total size of a specified file. skill Send a signal to processes. slabtop Show kernel slab cache information in real-time. slattach Attack a network interface to a serial line. sleep Suspend execution for a specified amount of time (in seconds). slocate Display matches by searching filename databases. Takes ownership and file permission into consideration. snice Reset priority for processes. sort Sort lines of text files. source Run commands from a specified file. split Split a file into pieces of fixed size. ss Display socket statistics, similar to netstat. ssh An SSH client for logging in to a remote machine. It provides encrypted communication between the hosts. ssh-add Adds private key identities to the authentication agent. ssh-agent It holds private keys used for public key authentication. ssh-keygen It generates, manages, converts authentication keys for ssh. ssh-keyscan Gather ssh public keys. sshd Server for the ssh program. stat Display file or filesystem status. statd A daemon that listens for reboot notifications from other hosts, and manages the list of hosts to be notified when the local system reboots. strace Trace system calls and signals. strfile Create a random access file for storing strings. strings Search a specified file and prints any printable strings with at least four characters and followed by an unprintable character. strip Discard symbols from object files. stty Change and print terminal line settings. su Change user ID or become superuser. sudo Execute a command as superuser. sum Checksum and count the block in a file. suspend Suspend the execution of the current shell. swapoff Disable devices for paging and swapping. swapon Enable devices for paging and swapping. symlink Create a symbolic link to a file. sync Synchronize cached writes to persistent storage. sysctl Configure kernel parameters at runtime. sysklogd Linux system logging utilities. Provides syslogd and klogd functionalities. syslogd Read and log system messages to the system console and log files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) T Command Description tac Concatenate and print files in reverse order. Opposite of cat command. tail Show the last 10 lines of each specified file(s). tailf Follow the growth of a log file. (Deprecated command) talk A two-way screen-oriented communication utility that allows two user to exchange messages simultaneously. talkd A remote user communication server for talk . tar GNU version of the tar archiving utility. Used to store and extract multiple files from a single archive. taskset Set/retrieve a process’s CPU affinity. tcpd Access control utility for internet services. tcpdump Dump traffic on network. Displays a description of the contents of packets on a network interface that match the boolean expression. tcpslice Extract pieces of tcpdump files or merge them. tee Read from standard input and write to standard output and files. telinit Change SysV runlevel. telnet Telnet protocol user interface. Used to interact with another host using telnet. telnetd A server for the telnet protocol. test Check file type and compare values. tftp User interface to the internet TFTP (Trivial File Transfer Protocol). tftpd TFTP server. time Run programs and summarize system resource usage. timeout Execute a command with a time limit. times Shows accumulated user and system times for the shell and it’s child processes. tload Shows a graph of the current system load average to the specified tty. tmpwatch Recursively remove files and directories which haven’t been accessed for the specified period of time. top Displays real-time view of processes running on the system. touch Change file access and modification times. tput Modify terminal-dependent capabilities, color, etc. tr Translate, squeeze, or delete characters from standard input and display on standard output. tracepath Traces path to a network host discovering MTU (Maximum Transmission Unit) along this path. traceroute Traces the route taken by the packets to reach the network host. trap Trap function responds to hardware signals. It defines and creates handlers to run when the shell receives signals. troff The troff processor of the groff text formatting system. TRUE Exit with a status code indicating success. tset Initialize terminal. tsort Perform topological sort. tty Display the filename of the terminal connected to standard input. tune2fs Adjust tuneable filesystem parameters on ext2/ext3/ext4 filesystems. tunelp Set various parameters for the line printer devices. type Write a description for a command type. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) U Command Description ul Underline text. ulimit Get and set user limits for the calling process. umask Set file mode creation mask. umount Unmount specified file systems. unalias Remove alias definitions for specified alias names. uname Show system information. uncompress Uncompress the files compressed with the compress command. unexpand Convert spaces to tabs for a specified file. unicode_start Put keyboard and console in Unicode mode. unicode_stop Revert keyboard and console from Unicode mode. uniq Report or omit repeating lines. units Convert units from one scalar to another. unrar Extract files from a RAR archive. unset Remove variable or function names. unshar Unpack shell archive scripts. until Execute command until a given condition is true. uptime Tell how long the system has been running. useradd Create a new user or update default user information. userdel Delete a user account and related files. usermod Modify a user account. users Show the list of active users on the machine. usleep Suspend execution for microsecond intervals. uudecode Decode a binary file. uuencode Encode a binary file. uuidgen Created a new UUID (Universally Unique Identifier) table. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) V Command Description vdir Same as ls -l -b . Verbosely list directory contents. vi A text editor utility. vidmode Set the video mode for a kernel image. Displays current mode value without arguments. Alternative: rdev -v vim Vi Improved, a text-based editor which is a successor to vi. vmstat Shows information about processes, memory, paging, block IO, traps, disks, and CPU activity. volname Returns volume name for a device formatted with an ISO-9660 filesystem. For example, CD-ROM. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) W Command Description w Show who is logged-on and what they’re doing. wait Waits for a specified process ID(s) to terminate and returns the termination status. wall Display a message on the terminals all the users who are currently logged-in. warnquota Send mail to the users who’ve exceeded their disk quota soft limit. watch Runs commands repeatedly until interrupted and shows their output and errors. wc Print newline, word, and byte count for each of the specified files. wget A non-interactive file download utility. whatis Display one line manual page descriptions. whereis Locate the binary, source, and man page files for a command. which For a given command, lists the pathnames for the files which would be executed when the command runs. while Conditionally execute commands (while loop). who Shows who is logged on. whoami Displays the username tied to the current effective user ID. whois Looks for an object in a WHOIS database write Display a message on other user’s terminal. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) X Command Description xargs Runs a command using initial arguments and then reads remaining arguments from standard input. xdg-open Used to open a file or URL in an application preferred by the user. xinetd Extended internet services daemon. Works similar to inetd. xz Compress/ Decompress .xz and .lzma files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Y Command Description yacc Yet Another Compiler Compiler, a GNU Project parser generator. yes Repeatedly output a line with a specified string(s) until killed. ypbind A daemon that helps client processes to connect to an NIS server. ypcat Shows the NIS map (or database) for the specified MapName parameter. ypinit Sets up NIS maps on an NIS server. ypmatch Shows values for specified keys from an NIS map. yppasswd Change NIS login password. yppasswdd Acts as a server for the yppasswd command. Receives and executes requests. yppoll Shows the ID number or version of NIS map currently used on the NIS server. yppush Forces slave NIS servers to copy updated NIS maps. ypserv A daemon activated at system startup. It looks for information in local NIS maps. ypset Point a client (running ypbind) to a specific server (running ypserv). yptest Calls various functions to check the configuration of NIS services. ypwhich Shows the hostname for NIS server or master server for a given map. ypxfr Transfers NIS server map from server to a local host. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Z Command Description zcat Used to compress/uncompress files. Similar to gzip zcmp Compare compressed files. zdiff Compare compressed files line by line. zdump Displays time for the timezone mentioned. zforce Adds .gz extension to all gzipped files. zgrep Performs grep on compressed files. zic Creates time conversion information files using the specified input files. zip A file compression and packaging utility. zless Displays information of a compressed file (using less command) on the terminal one screen at a time. zmore Displays output of a compressed file (using more command) on the terminal one page at a time. znew Recompress .z files to .gz. files. Credits: fossbytes.com [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Quick cheat sheet 📝 >**Note** > Examples like `-a|--all` option flags means, single `-` used for _short_ option(-a) **or**| double `--` used for _long_ option(--all). Both was added for educational purpose.### Contents- [Command Information](#command-information)- [Command History](#command-history)- [Navigating Directories](#navigating-directories)- [Creating Directories](#creating-directories)- [Moving Directories](#moving-directories)- [Deleting Directories](#deleting-directories)- [Creating Files](#creating-files)- [Standard Output, Error and Input](#standard-output-standard-error-and-standard-input)- [Moving Files](#moving-files)- [Deleting Files](#deleting-files)- [Reading Files](#reading-files)- [File Permissions](#file-permissions)- [Finding Files](#finding-files)- [Find in Files](#find-in-files)- [Replace in Files](#replace-in-files)- [Symbolic Links](#symbolic-links)- [Compressing Files](#compressing-files)- [Decompressing Files](#decompressing-files)- [Packages](#packages)- [Disk Usage](#disk-usage)- [Memory Usage](#memory-usage)- [Shutdown and Reboot](#shutdown-and-reboot)- [Identifying Processes](#identifying-processes)- [Process Priority](#process-priority)- [Killing Processes](#killing-processes)- [Date & Time](#date--time)- [Scheduled Tasks](#scheduled-tasks)- [User Mangement](#user-management)- [HTTP Requests](#http-requests)- [Network Troubleshooting](#network-troubleshooting)- [DNS](#dns)- [Hardware](#hardware)- [System Information](#system-information)- [Terminal Multiplexers](#terminal-multiplexers)- [Secure Shell Protocol (SSH)](#secure-shell-protocol-ssh)- [Secure Copy](#secure-copy)- [Bash Profile](#bash-profile)- [Bash Script](#bash-script)### Command Information```bashman chmod # Display page manual of a commandman -f|--whatis chmod # Display short description about a commandman -k|--apropos permission # Display all related commands from a specific keywordchmod --help # Display usage options of a command```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Command History```bashhistory # View all previous commandshistory | grep foo # View the commands using a specific wordhistory | grep -E|--extended-regexp -i|--ignore-case 'foo1|foo2|foo3' # View the commands using more than 1 specific word(case sensitive)history | head -n|--lines 3 # View the first 3 executed commandshistory 3 # View the last 3 executed commandshistory -d 99 # Clear a command from a specific line history -c # Clears all history commands!! # Run the last command executedtouch foo.sh # <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<┐chmod +x !$ # !$ is the last argument of the last command i.e. foo.sh <<<<┘```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Navigating Directories```bashpwd # Print current directory pathls # List directoriesls -a|--all # List directories including hiddenls -l # List directories in long formls -l -h|--human-readable # List directories in long form with human readable sizesls -t # List directories by modification time, newest firststat foo.txt # List size, created and modified timestamps for a filestat foo # List size, created and modified timestamps for a directorytree # List directory and file treetree -a # List directory and file tree including hiddentree -d # List directory treecd foo # Go to foo sub-directorycd # Go to home directorycd ~ # Go to home directorycd - # Go to last directorypushd foo # Go to foo sub-directory and add previous directory to stackpopd # Go back to directory in stack saved by `pushd````[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Creating Directories ```bashmkdir foo # Create a directorymkdir foo bar # Create multiple directoriesmkdir -p|--parents foo/bar # Create nested directorymkdir -p|--parents {foo,bar}/baz # Create multiple nested directoriesmktemp -d|--directory # Create a temporary directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Moving Directories```bashcp -R|--recursive foo bar # Copy directorymv foo bar # Move directoryrsync -z|--compress -v|--verbose /foo /bar # Copy directory, overwrites destinationrsync --ignore-existing -a|--archive-a|--archive -z|--compress -v|--verbose /foo /bar # Copy directory, without overwriting destinationrsync -avz /foo username@hostname:/bar # Copy local directory to remote directoryrsync -avz username@hostname:/foo /bar # Copy remote directory to local directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Deleting Directories```bashrmdir foo # Delete non-empty directoryrm -r|--recursive foo # Delete directory including contentsrm -r|--recursive -f|--force foo # Delete directory including contents, ignore nonexistent files and never prompt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Creating Files```bashtouch foo.txt # Create file or update existing files modified timestamptouch foo.txt bar.txt # Create multiple filestouch {foo,bar}.txt # Create multiple filestouch test{1..3} # Create test1, test2 and test3 filestouch test{a..c} # Create testa, testb and testc filesmktemp # Create a temporary file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Standard Output, Standard Error and Standard Input```bashecho "foo" > bar.txt # Overwrite file with contentecho "foo" >> bar.txt # Append to file with contentls exists 1> stdout.txt # Redirect the standard output to a filels noexist 2> stderror.txt # Redirect the standard error output to a filels > out.txt 2>&1 # Redirect standard output and error to a filels > /dev/null # Discard standard output and errorread foo # Read from standard input and write to the variable foo```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Moving Files```bashcp foo.txt bar.txt # Copy filemv foo.txt bar.txt # Move filersync -z|--compress -v|--verbose /foo.txt /bar # Copy file quickly if not changedrsync -z|--compress -v|--verbose /foo.txt /bar.txt # Copy and rename file quickly if not changed```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Deleting Files```bashrm foo.txt # Delete filerm -f|--force foo.txt # Delete file, ignore nonexistent files and never prompt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Reading Files```bashcat foo.txt # Print all contentsless foo.txt # Print some contents at a time (g - go to top of file, SHIFT+g, go to bottom of file, /foo to search for 'foo')head foo.txt # Print top 10 lines of filetail foo.txt # Print bottom 10 lines of filetail -f foo.txt # Print bottom 10 lines of file updating with new dataopen foo.txt # Open file in the default editorwc foo.txt # List number of lines words and characters in the file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## File Permissions| # | Permission | rwx | Binary || - | - | - | - || 7 | read, write and execute | rwx | 111 || 6 | read and write | rw- | 110 || 5 | read and execute | r-x | 101 || 4 | read only | r-- | 100 || 3 | write and execute | -wx | 011 || 2 | write only | -w- | 010 || 1 | execute only | --x | 001 || 0 | none | --- | 000 |For a directory, execute means you can enter a directory.| User | Group | Others | Description || - | - | - | - || 6 | 4 | 4 | User can read and write, everyone else can read (Default file permissions) || 7 | 5 | 5 | User can read, write and execute, everyone else can read and execute (Default directory permissions) |- u - User- g - Group- o - Others- a - All of the above```bashls -l /foo.sh # List file permissionschmod +100 foo.sh # Add 1 to the user permissionchmod -100 foo.sh # Subtract 1 from the user permissionchmod u+x foo.sh # Give the user execute permissionchmod g+x foo.sh # Give the group execute permissionchmod u-x,g-x foo.sh # Take away the user and group execute permissionchmod u+x,g+x,o+x foo.sh # Give everybody execute permissionchmod a+x foo.sh # Give everybody execute permissionchmod +x foo.sh # Give everybody execute permission```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Finding FilesFind binary files for a command.```bashtype -a wget # Display all locations of executablewhich -a wget # Display all locations of executables whereis wget # Find the binary, source, and manual page files````locate` uses an index and is fast.```bashupdatedb # Update the indexlocate foo.txt # Find a filelocate --ignore-case # Find a file and ignore caselocate f*.txt # Find a text file starting with 'f'````find` doesn't use an index and is slow.```bashfind /path -name foo.txt # Find a filefind /path -iname foo.txt # Find a file with case insensitive searchfind /path -name "*.txt" # Find all text filesfind /path -name foo.txt -delete # Find a file and delete itfind /path -name "*.png" -exec pngquant {} # Find all .png files and execute pngquant on itfind /path -type f -name foo.txt # Find a filefind /path -type d -name foo # Find a directoryfind /path -type l -name foo.txt # Find a symbolic linkfind /path -type f -mtime +30 # Find files that haven't been modified in 30 daysfind /path -type f -mtime +30 -delete # Delete files that haven't been modified in 30 days```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Find in Files```bashgrep 'foo' /bar.txt # Search for 'foo' in file 'bar.txt'grep 'foo' /bar -r|--recursive # Search for 'foo' in directory 'bar'grep 'foo' /bar -R|--dereference-recursive # Search for 'foo' in directory 'bar' and follow symbolic linksgrep 'foo' /bar -l|--files-with-matches # Show only files that matchgrep 'foo' /bar -L|--files-without-match # Show only files that don't matchgrep 'Foo' /bar -i|--ignore-case # Case insensitive searchgrep 'foo' /bar -x|--line-regexp # Match the entire linegrep 'foo' /bar -C|--context 1 # Add N line of context above and below each search resultgrep 'foo' /bar -v|--invert-match # Show only lines that don't matchgrep 'foo' /bar -c|--count # Count the number lines that matchgrep 'foo' /bar -n|--line-number # Add line numbersgrep 'foo' /bar --colour # Add colour to outputgrep 'foo\|bar' /baz -R # Search for 'foo' or 'bar' in directory 'baz'grep --extended-regexp|-E 'foo|bar' /baz -R # Use regular expressionsgrep -E 'foo|bar' /baz -R # Use regular expressions```### Replace in Files```bashsed 's/fox/bear/g' foo.txt # Replace fox with bear in foo.txt and output to consolesed 's/fox/bear/gi' foo.txt # Replace fox (case insensitive) with bear in foo.txt and output to consolesed 's/red fox/blue bear/g' foo.txt # Replace red with blue and fox with bear in foo.txt and output to consolesed 's/fox/bear/g' foo.txt > bar.txt # Replace fox with bear in foo.txt and save in bar.txtsed 's/fox/bear/g' foo.txt -i|--in-place # Replace fox with bear and overwrite foo.txt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Symbolic Links```bashln -s|--symbolic foo bar # Create a link 'bar' to the 'foo' folderln -s|--symbolic -f|--force foo bar # Overwrite an existing symbolic link 'bar'ls -l # Show where symbolic links are pointing```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Compressing Files### zipCompresses one or more files into *.zip files.```bashzip foo.zip /bar.txt # Compress bar.txt into foo.zipzip foo.zip /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.zipzip foo.zip /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.zipzip -r|--recurse-paths foo.zip /bar # Compress directory bar into foo.zip```### gzipCompresses a single file into *.gz files.```bashgzip /bar.txt foo.gz # Compress bar.txt into foo.gz and then delete bar.txtgzip -k|--keep /bar.txt foo.gz # Compress bar.txt into foo.gz```### tar -cCompresses (optionally) and combines one or more files into a single *.tar, *.tar.gz, *.tpz or *.tgz file.```bashtar -c|--create -z|--gzip -f|--file=foo.tgz /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.tgztar -c|--create -z|--gzip -f|--file=foo.tgz /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.tgztar -c|--create -z|--gzip -f|--file=foo.tgz /bar # Compress directory bar into foo.tgz```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Decompressing Files### unzip```bashunzip foo.zip # Unzip foo.zip into current directory```### gunzip```bashgunzip foo.gz # Unzip foo.gz into current directory and delete foo.gzgunzip -k|--keep foo.gz # Unzip foo.gz into current directory```### tar -x```bashtar -x|--extract -z|--gzip -f|--file=foo.tar.gz # Un-compress foo.tar.gz into current directorytar -x|--extract -f|--file=foo.tar # Un-combine foo.tar into current directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Packages```bashapt update # Refreshes repository indexapt search wget # Search for a packageapt show wget # List information about the wget packageapt list --all-versions wget # List all versions of the packageapt install wget # Install the latest version of the wget packageapt install wget=1.2.3 # Install a specific version of the wget packageapt remove wget # Removes the wget packageapt upgrade # Upgrades all upgradable packagesapt clean # Clears out the local repository of downloaded package filesdpkg -i|--install package_name.deb # Install deb filerpm -i|--install package_name.rpm # Install rpm file ```### Install package source code```bashtar zxvf sourcecode.tar.gzcd sourcecode./configuremakemake install```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Disk Usage```bashdf # List disks, size, used and available spacedf -h|--human-readable # List disks, size, used and available space in a human readable formatdu # List current directory, subdirectories and file sizesdu /foo/bar # List specified directory, subdirectories and file sizesdu -h|--human-readable # List current directory, subdirectories and file sizes in a human readable formatdu -d|--max-depth # List current directory, subdirectories and file sizes within the max depthdu -d 0 # List current directory size```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Memory Usage```bashfree # Show memory usagefree -h|--human # Show human readable memory usagefree -h|--human --si # Show human readable memory usage in power of 1000 instead of 1024free -s|--seconds 5 # Show memory usage and update continuously every five seconds```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Shutdown and Reboot```bashshutdown # Shutdown in 1 minuteshutdown now # Immediately shut downshutdown +5 # Shutdown in 5 minutesshutdown -r|--reboot # Reboot in 1 minuteshutdown -r|--reboot now # Immediately rebootshutdown -r|--reboot +5 # Reboot in 5 minutesshutdown -c # Cancel a shutdown or rebootreboot # Reboot nowreboot -f # Force a reboot```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Identifying Processes```bashtop # List all processes interactivelyhtop # List all processes interactivelyps ax # List all processespidof foo # Return the PID of all foo processesCTRL+Z # Suspend a process running in the foregroundbg # Resume a suspended process and run in the backgroundfg # Bring the last background process to the foregroundfg 1 # Bring the background process with the PID to the foregroundsleep 30 & # Sleep for 30 seconds and move the process into the backgroundjobs # List all background jobsjobs -p # List all background jobs with their PIDlsof # List all open files and the process using themlsof -itcp:4000 # Return the process listening on port 4000```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Process PriorityProcess priorities go from -20 (highest) to 19 (lowest).```bashnice -n -20 foo # Change process priority by namerenice 20 PID # Change process priority by PIDps -o ni PID # Return the process priority of PID```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Killing Processes```bashCTRL+C # Kill a process running in the foregroundkill PID # Shut down process by PID gracefully. Sends TERM signal.kill -9 PID # Force shut down of process by PID. Sends SIGKILL signal.pkill foo # Shut down process by name gracefully. Sends TERM signal.pkill -9 foo # force shut down process by name. Sends SIGKILL signal.killall foo # Kill all process with the specified name gracefully.```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Date & Time```bashdate # Print the date and timedate --iso-8601 # Print the ISO8601 datedate --iso-8601=ns # Print the ISO8601 date and timedate -s "02 DEC 2020 12:02:02" # Manually change date and timedpkg-reconfigure tzdata # Change date/timezoneuptime # Print how long the system has been runningtime tree # Print amount of time to tree takes to execute```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Scheduled Tasks```pre * * * * *Minute, Hour, Day of month, Month, Day of the week``````bashcrontab -l # List cron tabcrontab -e # Edit cron tab in Vimcrontab /path/crontab # Load cron tab from a filecrontab -l > /path/crontab # Save cron tab to a file* * * * * foo # Run foo every minute*/15 * * * * foo # Run foo every 15 minutes0 * * * * foo # Run foo every hour15 6 * * * foo # Run foo daily at 6:15 AM44 4 * * 5 foo # Run foo every Friday at 4:44 AM0 0 1 * * foo # Run foo at midnight on the first of the month0 0 1 1 * foo # Run foo at midnight on the first of the yearat -l # List scheduled tasksat -c 1 # Show task with ID 1at -r 1 # Remove task with ID 1at now + 2 minutes # Create a task in Vim to execute in 2 minutesat 12:34 PM next month # Create a task in Vim to execute at 12:34 PM next monthat tomorrow # Create a task in Vim to execute tomorrow```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## User Management```bashadduser username # To add a new userpasswd -l|--lock username # To change the password of a useruserdel username # To remove useruserdel -r|--remove username # To remove user with home directory and mail spoolusermod -a|--append -G|--groups GROUPNAME USERNAME # To add a user to a groupdeluser USER GROUPNAME # To remove a user from a grouplast # Shows information of all the users logged inlast username # Gives information of a particular user```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## HTTP Requests```bashcurl https://example.com # Return response bodycurl -i|--include https://example.com # Include status code and HTTP headerscurl -L|--location https://example.com # Follow redirectscurl -O|--remote-name foo.txt https://example.com # Output to a text filecurl -H|--header "User-Agent: Foo" https://example.com # Add a HTTP headercurl -X|--request POST -H "Content-Type: application/json" -d|--data '{"foo":"bar"}' https://example.com # POST JSONcurl -X POST -H --data-urlencode foo="bar" http://example.com # POST URL Form Encodedwget https://example.com/file.txt # Download a file to the current directorywget -O|--output-document foo.txt https://example.com/file.txt # Output to a file with the specified name```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Network Troubleshooting```bashping example.com # Send multiple ping requests using the ICMP protocolping -c 10 -i 5 example.com # Make 10 attempts, 5 seconds apartip addr # List IP addresses on the systemip route show # Show IP addresses to routercurl ifconfig.me # Obtain external IP addressnetstat -i|--interfaces # List all network interfaces and in/out usagenetstat -l|--listening # List all open portstraceroute example.com # List all servers the network traffic goes throughmtr -w|--report-wide example.com # Continually list all servers the network traffic goes throughmtr -r|--report -w|--report-wide -c|--report-cycles 100 example.com # Output a report that lists network traffic 100 timesnmap 0.0.0.0 # Scan for the 1000 most common open ports on localhostnmap 0.0.0.0 -p1-65535 # Scan for open ports on localhost between 1 and 65535nmap 192.168.4.3 # Scan for the 1000 most common open ports on a remote IP addressnmap -sP 192.168.1.1/24 # Discover all machines on the network by ping'ing them```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## DNS```bashdig example.com # Show query information of domain A recordsdig -4 example.com # Show IPv4 A recordsdig -6 example.com # Show IPv6 AAA recordsdig example.com @nameserver # Show query of a specific nameserverdig example.com -p 123 # Show query of a specific port numbercat /etc/resolv.conf # Nameservers filecat /etc/systemd/resolved.conf # DNS resolver config file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Hardware```bashlsusb # List USB deviceslspci # List PCI hardwarelshw # List all hardware```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## System Information```uname -s # Print kernel nameuname -r # Print kernel releaseuname -m # Print Architectureuname -o # Print Operating System```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Terminal MultiplexersStart multiple terminal sessions. Active sessions persist reboots. `tmux` is more modern than `screen`.```bashtmux # Start a new session (CTRL-b + d to detach)tmux ls # List all sessionstmux attach -t 0 # Reattach to a sessionscreen # Start a new session (CTRL-a + d to detach)screen -ls # List all sessionsscreen -R 31166 # Reattach to a sessionexit # Exit a session```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Secure Shell Protocol (SSH)```bashssh hostname # Connect to hostname using your current user name over the default SSH port 22ssh -i foo.pem hostname # Connect to hostname using the identity filessh user@hostname # Connect to hostname using the user over the default SSH port 22ssh user@hostname -p 8765 # Connect to hostname using the user over a custom portssh ssh://user@hostname:8765 # Connect to hostname using the user over a custom port```Set default user and port in `~/.ssh/config`, so you can just enter the name next time:```bash$ cat ~/.ssh/configHost name User foo Hostname 127.0.0.1 Port 8765$ ssh name```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Secure Copy```bashscp foo.txt ubuntu@hostname:/home/ubuntu # Copy foo.txt into the specified remote directoryscp ubuntu@hostname:/home/ubuntu/foo.txt /C:\Users\Admin # Copy foo.txt from the specified remote directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Bash Profile- bash - `.bashrc`- zsh - `.zshrc````bash# Always run ls after cdfunction cd { builtin cd "$@" && ls}# Prompt user before overwriting any filesalias cp='cp --interactive'alias mv='mv --interactive'alias rm='rm --interactive'# Always show disk usage in a human readable formatalias df='df -h'alias du='du -h'```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Bash Script### Variables```bash#!/bin/bashfoo=123 # Initialize variable foo with 123declare -i foo=123 # Initialize an integer foo with 123declare -r foo=123 # Initialize readonly variable foo with 123echo $foo # Print variable fooecho ${foo}_'bar' # Print variable foo followed by _barecho ${foo:-'default'} # Print variable foo if it exists otherwise print defaultexport foo # Make foo available to child processesunset foo # Make foo unavailable to child processes and current session```### Environment Variables```bash#!/bin/bashset # List all environment variablesecho $PATH # Print PATH environment variableexport FOO=Bar # Set an environment variable```### Functions```bash#!/bin/bashgreet() { local world="World" echo "$1 $world" return "$1 $world"}greet "Hello"greeting=$(greet "Hello")```### Exit Codes```bash#!/bin/bashexit 0 # Exit the script successfullyexit 1 # Exit the script unsuccessfullyecho $? # Print the last exit code```### Conditional Statements#### Boolean Operators- `$foo` - Is true- `!$foo` - Is false#### Numeric Operators- `-eq` - Equals- `-ne` - Not equals- `-gt` - Greater than- `-ge` - Greater than or equal to- `-lt` - Less than- `-le` - Less than or equal to- `-e` foo.txt - Check file exists- `-z` foo - Check if variable exists#### String Operators- `=` - Equals- `==` - Equals- `-z` - Is null- `-n` - Is not null- `<` - Is less than in ASCII alphabetical order- `>` - Is greater than in ASCII alphabetical order#### If Statements```bash#!/bin/bash[[if [[$foo = 'bar']]; then echo 'one'elif [[$foo = 'bar']] || [[$foo = 'baz']]; then echo 'two'elif [[$foo = 'ban']] && [[$USER = 'bat']]; then echo 'three'else echo 'four'fi]]```#### Inline If Statements```bash#!/bin/bash[[ $USER = 'rehan' ]] && echo 'yes' || echo 'no'```#### While Loops```bash#!/bin/bash[declare -i countercounter=10while [$counter -gt 2]; do echo The counter is $counter counter=counter-1done]```#### For Loops```bash#!/bin/bashfor i in {0..10..2} do echo "Index: $i" donefor filename in file1 file2 file3 do echo "Content: " >> $filename donefor filename in *; do echo "Content: " >> $filename done```#### Case Statements```bash#!/bin/bashecho "What's the weather like tomorrow?"read weathercase $weather in sunny | warm ) echo "Nice weather: " $weather ;; cloudy | cool ) echo "Not bad weather: " $weather ;; rainy | cold ) echo "Terrible weather: " $weather ;; * ) echo "Don't understand" ;;esac```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents) Special characters 🔣 Char. Description ~ Home directory [tilde]. The path to a user's home directory location. - Previous directory [dash]. Go back to previous directory. / Filename path separator [forward slash]. Separates the components of a filename. It also represents the path to root directory. \ Escape [backslash]. A quoting mechanism for single characters. It preserves the literal value of the next character that follows, with the exception of newline. │ Pipe. It passes the output (stdout) of a previous command to the input (stdin) of the next one, or to the shell. This is a method of chaining commands together. || The OR operator is used to chain commands. It will execute succeeded commands which follows and stops if the preceding command fails. && The AND operator is used to chain commands. It will execute commands only if the first command is successful ; Command separator [semicolon]. Used to separate multiple commands and execute all the ones that is successful. & Run job in background[and]. A command followed by an & will run in the background. # Comment [number sign]. Lines in files beginning with a # (with the exception of #!) are comments and will not be executed. >, >>, < Redirect a command's output or input into a file. >| Force redirection (even if the noclobber option is set). This will forcibly overwrite an existing file. ' ' Single quotes protects the text inside them so that it has a literal meaning. This is a stronger form of quoting than double quotes. " " Whitespace. This is a tab, newline, vertical tab, form feed, carriage return, or space. Bash uses whitespace to determine where words begin and end. ! Reverse (or negate) [exclamation]. The ! operator inverts the exit status of the command to which it is applied. It also inverts the meaning of a test operator. * Wild card [asterisk]. The * character serves as a "wild card" for filename expansion in globbing . By itself, it matches every filename in a given directory. ? Wild card [question mark]. The ? character serves as a single-character "wild card" for filename expansion in globbing, as well as representing one character in an extended regular expression. { } Inline group [curly brackets]. Commands inside the curly braces are treated as if they were one command. It is convenient to use these when Bash syntax requires only one command and a function doesn't feel warranted. ( ) Subshell group [bracket].Commands within are executed in a subshell (a new process) Used much like a sandbox, if a command causes side effects (like changing variables), it will have no effect on the current shell. [ ] Test expression between [ ]. It is part of the shell builtin test. [[ ]] Test expression between [[ ]]. It is more flexible than the single-bracket [ ] test. (( )) Integer expansion. Expand and evaluate integer expression. ;; Terminator in a case option [double semicolon]. ,, , Lowercase conversion in parameter substitution. ^, ^^ Uppercase conversion in parameter substitution. Keyboard controls ⌨️ | Key | Function || :--: | :-- || Ctrl+a | Moves cursor to beginning of text in line || Ctrl+e | Moves cursor to end of text in line || Ctrl+b | Moves cursor backward one character position || Ctrl+f | Moves cursor forward one character position || Ctrl+p | Fetch previous command from history list || Ctrl+n | Fetch next command from history list || Ctrl+d | Erase characters from cursor left to right || Ctrl+u | Erase a line of input from cursor right to left of line || Ctrl+k | Erase a line of input from cursor left to right of line || Ctrl+w | Erase backwards to first non-alphanumeric character or empty space || Ctrl+y | Fetch back command previously erased || Ctrl+t | Reverses the position of the character the cursor is on with the previous character || Ctrl+r | Reverse search commands from history list || Ctrl+z | Pauses a foreground job || Ctrl+c | Break/Terminate a foreground job || Ctrl+o | Accept the current line for execution and fetch the next command || Ctrl+l | Clear screen contents (command line needs to be empty) || Ctrl+s | Suspend || Ctrl+q | Resume || Ctrl+d | Log out from a shell (similar to exit) | Online Cheat Sheet :feelsgood: for quick references of commands and codes cheat.sh Terminal :```bashcurl cht.sh/keyword or curl cheat.sh/keyword``` Browser : https://cht.sh/ keyword or https://cheat.sh/ keyword # #### Offline usage Install cheat script manually Install globally(all users) : bashcurl -s https://cht.sh/:cht.sh | sudo tee /usr/local/bin/cht.sh && sudo chmod +x /usr/local/bin/cht.sh Run :```bashcht.sh keyword ``` To restore the repository download the bundle wget https://archive.org/download/github.com-trinib-Linux-Bash-Commands_-_2022-11-08_16-56-21/trinib-Linux-Bash-Commands_-_2022-11-08_16-56-21.bundle and run: git clone trinib-Linux-Bash-Commands_-_2022-11-08_16-56-21.bundle Source: https://github.com/trinib/Linux-Bash-Commands Uploader: trinib Upload date: 2022-11-08

------------------------------- Shop: http://www.hakshop.com Support: http://www.patreon.com/threatwire Subscribe: http://www.youtube.com/hak5 Our Site: http://www.hak5.org Contact Us: http://www.twitter.com/hak5 ------------------------------ In this episode of Hak5, Darren and Shannon check out a few more fun linux commands and offer some BASH tips! -~-~~-~~~-~~-~- Please watch: "Bash Bunny Primer - Hak5 2225" https://www.youtube.com/watch?v=8j6hrjSrJaM -~-~~-~~~-~~-~- Source: https://www.youtube.com/watch?v=mbrXsL8TUrU Uploader: Hak5

Master the Linux Command Line with Confidence - Your Ultimate Handbook for Efficiency and Productivity 

linux

TOP 50 COMMANDS LINUX

TOP 50 COMMANDS LINUX

:godmode: Ultimate list of Linux bash commands Ultimate list of Linux bash commands Bash is the Unix command-line interface (CLI). You'll also see it called the terminal, the command line, or the shell. It's a command language that allows us to work with files on our computers in a way that's far more efficient and powerful than using a GUI (graphical user interface) A to Z command list 📚 > **Note** > Use `Ctrl+f` to search in browsers🔎 Table #### │ [A](#-a) │ [B](#-b) │ [C](#-c) │ [D](#-d) │ [E](#-e) │ [F](#-f) │ [G](#-g) │ [H](#-h) │ [I](#-i) │ [J](#-j) │ [K](#-k) │ [L](#-l) │ [M](#-m) │ [N](#-n) │ [O](#-o) │ [P](#-p) │ [Q](#-q) │ [R](#-r) │ [S](#-s) │ [T](#-t) │ [U](#-u) │ [V](#-v) │ [W](#-w) │ [X](#-x) │ [Y](#-y) │ [Z](#-z) │ A Command Description accept  Accept or Reject jobs to a destination, such as a printer. access  Check a user’s RWX permission for a file. aclocal  GNU autoconf too aconnect  ALSA sequencer connection manager. acpi  Show information about the Advanced Configuration and Power Interface. acpi_available  Check if ACPI functionality exists on the system. acpid  Informs user-space programs about ACPI events. addr2line  Used to convert addresses into file names and line numbers. addresses  Formats for internet mail addresses. agetty  An alternative Linux Getty alias  Create an alias for Linux commands alsactl  Access advanced controls for ALSA soundcard driver. amidi  Perform read/write operation for ALSA RawMIDI ports. amixer  Access CLI-based mixer for ALSA soundcard driver. anacron  Used to run commands periodically. aplay  Sound recorder and player for CLI. aplaymidi  CLI utility used to play MIDI files. apm  Show Advanced Power Management (APM) hardware info on older systems. apmd  Used to handle events reported by APM BIOS drivers. apropos  Shows the list of all man pages containing a specific keyword apt  Advanced Package Tool, a package management system for Debian and derivatives. apt-get  Command-line utility to install/remove/update packages based on APT system. aptitude  Another utility to add/remove/upgrade packages based on the APT system. ar  A utility to create/modify/extract from archives. arch  Display print machine hardware name. arecord  Just like aplay, it’s a sound recorder and player for ALSA soundcard driver. arecordmidi  Record standard MIDI files. arp  Used to make changes to the system’s ARP cache as  A portable GNU assembler. aspell  An interactive spell checker utility. at  Used to schedule command execution at specified date & time, reading commands from an input file. atd  Used to execute jobs queued by the at command. atq  List a user’s pending jobs for the at command. atrm  Delete jobs queued by the at command. audiosend  Used to send an audio recording as an email. aumix  An audio mixer utility. autoconf  Generate configuration scripts from a TEMPLATE-FILE and send the output to standard output. autoheader  Create a template header for configure. automake  Creates GNU standards-compliant Makefiles from template files autoreconf  Update generated configuration files. autoscan  Generate a preliminary configure.in autoupdate  Update a configure.in file to newer autoconf. awk  Used to find and replace text in a file(s). [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) B Command Description badblocks  Search a disk partition for bad sectors. banner  Used to print characters as a poster. basename  Used to display filenames with directoy or suffix. bash  GNU Bourne-Again Shell. batch  Used to run commands entered on a standard input. bc  Access the GNU bc calculator utility. bg  Send processes to the background. biff  Notify about incoming mail and sender’s name on a system running comsat server. bind  Used to attach a name to a socket. bison  A GNU parser generator, compatible with yacc. break  Used to exit from a loop (eg: for, while, select). builtin  Used to run shell builtin commands, make custom functions for commands extending their functionality. bzcmp  Used to call the cmp program for bzip2 compressed files. bzdiff  Used to call the diff program for bzip2 compressed files. bzgrep  Used to call grep for bzip2 compressed files. bzip2  A block-sorting file compressor used to shrink given files. bzless  Used to apply ‘less’ (show info one page at a time) to bzip2 compressed files. bzmore  Used to apply ‘more’ (an inferior version of less) to bzip2 compressed files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) C Command Description cal  Show calendar. cardctl  Used to control PCMCIA sockets and select configuration schemes. cardmgr  Keeps an eye on the added/removes sockets for PCMCIA devices. case  Execute a command conditionally by matching a pattern. cat  Used to concatenate files and print them on the screen. cc  GNU C and C++ compiler. cd  Used to change directory. cdda2wav  Used to rip a CD-ROM and make WAV file. cdparanoia  Record audio from CD more reliably using data-verification algorithms. cdrdao  Used to write all the content specified to a file to a CD all at once. cdrecord  Used to record data or audio compact discs. cfdisk  Show or change the disk partition table. chage  Used to change user password information. chattr  Used to change file attributes. chdir  Used to change active working directory. chfn  Used to change real user name and information. chgrp  Used to change group ownership for file. chkconfig  Manage execution of runlevel services. chmod  Change access permission for a file(s). chown  Change the owner or group for a file. chpasswd  Update password in a batch. chroot  Run a command with root directory. chrt  Alter process attributed in real-time. chsh  Switch login shell. chvt  Change foreground virtual terminal. cksum  Perform a CRC checksum for files. clear  Used to clear the terminal window. cmp  Compare two files (byte by byte). col  Filter reverse (and half-reverse) line feeds from the input. colcrt  Filter nroff output for CRT previewing. colrm  Remove columns from the lines of a file. column  A utility that formats its input into columns. comm  Used to compare two sorted files line by line. command  Used to execute a command with arguments ignoring shell function named command. compress  Used to compress one or more file(s) and replacing the originals ones. continue  Resume the next iteration of a loop. cp  Copy contents of one file to another. cpio  Copy files from and to archives. cpp  GNU C language processor. cron  A daemon to execute scheduled commands. crond  Same work as cron. crontab  Manage crontab files (containing schedules commands) for users. csplit  Split a file into sections on the basis of context lines. ctags  Make a list of functions and macro names defined in a programming source file. cupsd  A scheduler for CUPS. curl  Used to transfer data from or to a server using supported protocols. cut  Used to remove sections from each line of a file(s). cvs  Concurrent Versions System. Used to track file versions, allow storage/retrieval of previous versions, and enables multiple users to work on the same file. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) D Command Description date  Show system date and time. dc  Desk calculator utility. dd  Used to convert and copy a file, create disk clone, write disk headers, etc. ddrescue  Used to recover data from a crashed partition. deallocvt  Deallocates kernel memory for unused virtual consoles. debugfs  File system debugger for ext2/ext3/ext4 declare  Used to declare variables and assign attributes. depmod  Generate modules.dep and map files. devdump  Interactively displays the contents of device or file system ISO. df  Show disk usage. diff  Used to compare files line by line. diff3  Compare three files line by line. dig  Domain Information Groper, a DNS lookup utility. dir  List the contents of a directory. dircolors  Set colors for ‘ls’ by altering the LS_COLORS environment variable. dirname  Display pathname after removing the last slash and characters thereafter. dirs  Show the list of remembered directories. disable  Restrict access to a printer. dlpsh  Interactive Desktop Link Protocol (DLP) shell for PalmOS. dmesg  Examine and control the kernel ring buffer. dnsdomainname  Show the DNS domain name of the system. dnssec-keygen  Generate encrypted Secure DNS keys for a given domain name. dnssec-makekeyset  Produce domain key set from one or more DNS security keys generated by dnssec-keygen. dnssec-signkey  Sign a secure DNS keyset with key signatures specified in the list of key-identifiers. dnssec-signzone  Sign a secure DNS zonefile with the signatures in the specified list of key-identifiers. doexec  Used to run an executable with an arbitrary argv list provided. domainname  Show or set the name of current NIS (Network Information Services) domain. dosfsck  Check and repair MS-DOS file systems. du  Show disk usage summary for a file(s). dump  Backup utility for ext2/ext3 file systems. dumpe2fs  Dump ext2/ext3/ext4 file systems. dumpkeys  Show information about the keyboard driver’s current translation tables. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) E Command Desription e2fsck  Used to check ext2/ext3/ext4 file systems. e2image  Store important ext2/ext3/ext4 filesystem metadata to a file. e2label  Show or change the label on an ext2/ext3/ext4 filesystem. echo  Send input string(s) to standard output i.e. display text on the screen. ed  GNU Ed – a line-oriented text editor. edquota  Used to edit filesystem quotas using a text editor, such as vi. egrep  Search and display text matching a pattern. eject  Eject removable media. elvtune  Used to set latency in the elevator algorithm used to schedule I/O activities for specified block devices. emacs Emacs text editor command line utility. enable  Used to enable/disable shell builtin commands. env  Run a command in a modified environment. Show/set/delete environment variables. envsubst  Substitute environment variable values in shell format strings. esd  Start the Enlightenment Sound Daemon (EsounD or esd). Enables multiple applications to access the same audio device simultaneously. esd-config Manage EsounD configuration. esdcat  Use EsounD to send audio data from a specified file. esdctl  EsounD control program. esddsp  Used to reroute non-esd audio data to esd and control all the audio using esd. esdmon  Used to copy the sound being sent to a device. Also, send it to a secondary device. esdplay  Use EsounD system to play a file. esdrec  Use EsounD to record audio to a specified file. esdsample  Sample audio using esd. etags  Used to create a list of functions and macros from a programming source file. These etags are used by emacs. For vi, use ctags. ethtool  Used to query and control network driver and hardware settings. eval  Used to evaluate multiple commands or arguments are once. ex  Interactive command exec  An interactive line-based text editor. exit  Exit from the terminal. expand  Convert tabs into spaces in a given file and show the output. expect  An extension to the Tcl script, it’s used to automate interaction with other applications based on their expected output. export  Used to set an environment variable. expr  Evaluate expressions and display them on standard output. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) F Command Description factor  Display prime factors of specified integer numbers. false  Do nothing, unsuccessfully. Exit with a status code indicating failure. fc-cache  Make font information cache after scanning the directories. fc-list  Show the list of available fonts. fdformat  Do a low-level format on a floppy disk. fdisk  Make changes to the disk partition table. fetchmail  Fetch mail from mail servers and forward it to the local mail delivery system. fg  Used to send a job to the foreground. fgconsole  Display the number of the current virtual console. fgrep  Display lines from a file(s) that match a specified string. A variant of grep. file  Determine file type for a file. find  Do a file search in a directory hierarchy. finger  Display user data including the information listed in .plan  and .project  in each user’s home directory. fingerd  Provides a network interface for the finger program. flex  Generate programs that perform pattern-matching on text. fmt  Used to convert text to a specified width by filling lines and removing new lines, displaying the output. fold  Wrap input line to fit in a specified width. for  Expand words and run commands for each one in the resultant list. formail  Used to filter standard input into mailbox format. format  Used to format disks. free  Show free and used system memory. fsck  Check and repair a Linux file system ftp  File transfer protocol user interface. ftpd  FTP server process. function  Used to define function macros. fuser  Find and kill a process accessing a file. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) G Command Description g++  Run the g++ compiler. gawk  Used for pattern scanning and language processing. A GNU implementation of AWK language. gcc  A C and C++ compiler by GNU. gdb  A utility to debug programs and know about where it crashes. getent  Shows entries from Name Service Switch Libraries for specified keys. getkeycodes  Displays the kernel scancode-to-keycode mapping table. getopts  A utility to parse positional parameters. gpasswd  Allows an administrator to change group passwords. gpg  Enables encryption and signing services as per the OpenPGP standard. gpgsplit  Used to split an OpenPGP message into packets. gpgv  Used to verify OpenPGP signatures. gpm  It enables cut and paste functionality and a mouse server for the Linux console. gprof  Shows call graph profile data. grep  Searches input files for a given pattern and displays the relevant lines. groff  Serves as the front-end of the groff document formatting system. groffer  Displays groff files and man pages. groupadd  Used to add a new user group. groupdel  Used to remove a user group. groupmod  Used to modify a group definition. groups  Show the group(s) to which a user belongs. grpck  Verifies the integrity of group files. grpconv  Creates a gshadow file from a group or an already existing gshadow. gs  Invokes Ghostscript, and interpreter and previewer for Adobe’s PostScript and PDF languages. gunzip  A utility to compress/expand files. gzexe  Used compress executable files in place and have them automatically uncompress and run at a later stage. gzip  Same as gzip. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) H Command Description halt  Command used to half the machine. hash  Shows the path for the commands executed in the shell. hdparm  Show/configure parameters for SATA/IDE devices. head  Shows first 10 lines from each specified file. help  Display’s help for a built-in command. hexdump  Shows specified file output in hexadecimal, octal, decimal, or ASCII format. history  Shows the command history. host  A utility to perform DNS lookups. hostid  Shows host’s numeric ID in hexadecimal format. hostname  Display/set the hostname of the system. htdigest  Manage the user authentication file used by the Apache web server. htop  An interactive process viewer for the command line. hwclock  Show or configure the system’s hardware clock. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) I Command Description iconv  Convert text file from one encoding to another. id  Show user and group information for a specified user. if  Execute a command conditionally. ifconfig  Used to configure network interfaces. ifdown  Stops a network interface. ifup  Starts a network interface. imapd  An IMAP (Interactive Mail Access Protocol) server daemon. import  Capture an X server screen and saves it as an image. inetd  Extended internet services daemon, it starts the programs that provide internet services. info  Used to read the documentation in Info format. init  Systemd system and service manager. insmod  A program that inserts a module into the Linux kernel. install  Used to copy files to specified locations and set attributions during the install process. iostat  Shows statistics for CPU, I/O devices, partitions, network filesystems. ip  Display/manipulate routing, devices, policy, routing and tunnels. ipcrm  Used to remove System V interprocess communication (IPC) objects and associated data structures. ipcs  Show information on IPC facilities for which calling process has read access. iptables  Administration tool for IPv4 packet filtering and NAT. iptables-restore  Used to restore IP tables from data specified in the input or a file. iptables-save  Used to dump IP table contents to standard output. isodump  A utility that shows the content iso9660 images to verify the integrity of directory contents. isoinfo  A utility to perform directory like listings of iso9660 images. isosize  Show the length of an iso9660 filesystem contained in a specified file. isovfy  Verifies the integrity of an iso9660 image. ispell  A CLI-based spell-check utility. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) J Command Description jobs  Show the list of active jobs and their status. join  For each pair of input lines, join them using a command field and display on standard output. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) K Command Description kbd_mode  Set a keyboard mode. Without arguments, shows the current keyboard mode. kbdrate  Reset keyboard repeat rate and delay time. kill  Send a kill (termination) signal to one more processes. killall  Kills a process(es) running a specified command. killall5  A SystemV killall command. Kills all the processes excluding the ones which it depends on. klogd  Control and prioritize the kernel messages to be displayed on the console, and log them through syslogd. kudzu  Used to detect new and enhanced hardware by comparing it with existing database. Only for RHEL and derivates. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) L Command Description last  Shows a list of recent logins on the system by fetching data from /var/log/wtmp file. lastb  Shows the list of bad login attempts by fetching data from /var/log/btmp  file. lastlog  Displays information about the most recent login of all users or a specified user. ld  The Unix linker, it combines archives and object files. It then puts them into one output file, resolving external references. ldconfig  Configure dynamic linker run-time bindings. ldd  Shows shared object dependencies. less  Displays contents of a file one page at a time. It’s advanced than more command. lesskey  Used to specify key bindings for less command. let  Used to perform integer artithmetic on shell variables. lftp  An FTP utility with extra features. lftpget  Uses lftop to retrieve HTTP, FTP, and other protocol URLs supported by lftp. link  Create links between two files. Similar to ln command. ln  Create links between files. Links can be hard (two names for the same file) or soft (a shortcut of the first file). loadkeys  Load keyboard translation tables. local  Used to create function variables. locale  Shows information about current or all locales. locate  Used to find files by their name. lockfile  Create semaphore file(s) which can be used to limit access to a file. logger  Make entries in the system log. login  Create a new session on the system. logname  Shows the login name of the current user. logout  Performs the logout operation by making changes to the utmp and wtmp files. logrotate  Used for automatic rotation, compression, removal, and mailing of system log files. look  Shows any lines in a file containing a given string in the beginning. losetup  Set up and control loop devices. lpadmin  Used to configure printer and class queues provided by CUPS (Common UNIX Printing System). lpc  Line printer control program, it provides limited control over CUPS printer and class queues. lpinfo  Shows the list of avaiable devices and drivers known to the CUPS server. lpmove  Move on or more printing jobs to a new destination. lpq  Shows current print queue status for a specified printer. lpr  Used to submit files for printing. lprint  Used to print a file. lprintd  Used to abort a print job. lprintq  List the print queue. lprm  Cancel print jobs. lpstat  Displays status information about current classes, jobs, and printers. ls  Shows the list of files in the current directory. lsattr  Shows file attributes on a Linux ext2 file system. lsblk  Lists information about all available or the specified block devices. lsmod  Show the status of modules in the Linux kernel. lsof  List open files. lspci  List all PCI devices. lsusb  List USB devices. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) M Command Description m4  Macro processor. mail  Utility to compose, receive, send, forward, and reply to emails. mailq  Shows to list all emails queued for delivery (sendmail queue). mailstats  Shows current mail statistics. mailto  Used to send mail with multimedia content in MIME format. make  Utility to maintain groups of programs, recompile them if needed. makedbm  Creates an NIS (Network Information Services) database map. makemap  Creates database maps used by the keyed map lookups in sendmail. man  Shows manual pages for Linux commands. manpath  Determine search path for manual pages. mattrib  Used to change MS-DOS file attribute flags. mbadblocks  Checks MD-DOS filesystems for bad blocks. mcat  Dump raw disk image. mcd  Used to change MS-DOS directory. mcopy  Used to copy MS-DOS files from or to Unix. md5sum  Used to check MD5 checksum for a file. mdel, mdeltree  Used to delete MS-DOS file. mdeltree recursively deletes MS-DOS directory and its contents. mdir  Used to display an MS-DOS directory. mdu  Used to display the amount of space occupied by an MS-DOS directory. merge  Three-way file merge. Includes all changes from file2 and file3 to file1. mesg  Allow/disallow osends to sedn write messages to your terminal. metamail For sending and showing rich text or multimedia email using MIME typing metadata. metasend   An interface for sending non-text mail. mformat  Used to add an MS-DOS filesystem to a low-level formatted floppy disk. mimencode  Translate to/from MIME multimedia mail encoding formats. minfo  Display parameters of an MS-DOS filesystem. mkdir  Used to create directories. mkdosfs  Used to create an MS-DOS filesystem under Linux. mke2fs  Used create an ext2/ext3/ext4 filesystem. mkfifo  Used to create named pipes (FIFOs) with the given names. mkfs  Used to build a Linux filesystem on a hard disk partition. mkfs.ext3  Same as mke2fs, create an ext3 Linux filesystem. mkisofs  Used to create an ISO9660/JOLIET/HFS hybrid filesystem. mklost+found  Create a lost+found directory on a mounted ext2 filesystem. mkmanifest  Makes a list of file names and their DOS 8.3 equivalent. mknod  Create a FIFO, block (buffered) special file, character (unbuffered) special file with the specified name. mkraid  Used to setup RAID device arrays. mkswap  Set up a Linux swap area. mktemp  Create a temporary file or directory. mlabel  Make an MD-DOS volume label. mmd  Make an MS-DOS subdirectory. mmount  Mount an MS-DOS disk. mmove  Move or rename an MS-DOS file or subdirectory. mmv  Mass move and rename files. modinfo  Show information about a Linux kernel module. modprobe  Add or remove modules from the Linux kernel. more  Display content of a file page-by-page. most  Browse or page through a text file. mount  Mount a filesystem. mountd  NFS mount daemon. mpartition  Partition an MS-DOS disk. mpg123  Command-line mp3 player. mpg321  Similar to mpg123. mrd  Remove an MS-DOS subdirectory. mren  Rename an existing MS-DOS file. mshowfat  Show FTA clusters allocated to a file. mt  Control magnetic tape drive operation. mtools  Utilities to access MS-DOS disks. mtoolstest  Tests and displays the mtools configuration files. mtr  A network diagnostic tool. mtype  Display contents of an MS-DOS file. mv  Move/rename files or directories. mzip  Change protection mode and eject disk on Zip/Jaz drive. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) N Command Description named  Internet domain name server. namei  Follow a pathname until a terminal point is found. nameif  Name network interfaces based on MAC addresses. nc  Netcat utility. Arbitrary TCP and UDP connections and listens. netstat  Show network information. newaliases  Rebuilds mail alias database. newgrp  Log-in to a new group. newusers  Update/create new users in batch. nfsd  Special filesystem for controlling Linux NFS server. nfsstat  List NFS statistics. nice  Run a program with modified scheduling priority. nl  Show numbered line while displaying the contents of a file. nm  List symbols from object files. nohup  Run a command immune to hangups. notify-send  A program to send desktop notifications. nslookup  Used performs DNS queries. Read this article for more info. nsupdate  Dynamic DNS update utility. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) O Command Description objcopy  Copy and translate object files. objdump  Display information from object files. od  Dump files in octal and other formats. op  Operator access, allows system administrators to grant users access to certain root operations that require superuser privileges. open  Open a file using its default application. openvt  Start a program on a new virtual terminal (VT). [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) P Command Description passwd  Change user password. paste  Merge lines of files. Write to standard output, TAB-separated lines consisting of sqentially correspnding lines from each file. patch  Apply a patchfile (containing differences listing by diff program) to an original file. pathchk  Check if file names are valid or portable. perl  Perl 5 language interpreter. pgrep  List process IDs matching the specified criteria among all the running processes. pidof  Find process ID of a running program. ping  Send ICMP ECHO_REQUEST to network hosts. pinky  Lightweight finger. pkill  Send kill signal to processes based on name and other attributes. pmap  Report memory map of a process. popd  Removes directory on the head of the directory stack and takes you to the new directory on the head. portmap  Converts RPC program numbers to IP port numbers. poweroff  Shuts down the machine. pppd  Point-to-point protocol daemon. pr  Convert (column or paginate) text files for printing. praliases  Prints the current system mail aliases. printcap  Printer capability database. printenv  Show values of all or specified environment variables. printf  Show arguments formatted according to a specified format. ps  Report a snapshot of the current processes. ptx  Produce a permuted index of file contents. pushd  Appends a given directory name to the head of the stack and then cd to the given directory. pv  Monitor progress of data through a pipe. pwck  Verify integrity of password files. pwconv  Creates shadow from passwd and an optionally existing shadow. pwd  Show current directory. python [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Q Command Description quota  Shows disk usage, and space limits for a user or group. Without arguments, only shows user quotas. quotacheck  Used to scan a file system for disk usage. quotactl  Make changes to disk quotas. quotaoff  Enable enforcement of filesystem quotas. quotaon  Disable enforcement of filesystem quotas. quotastats  Shows the report of quota system statistics gathered from the kernel. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) R Command Description raidstart  Start/stop RAID devices. ram  RAM disk device used to access the RAM disk in raw mode. ramsize  Show usage information for the RAM disk. ranlib  Generate index to the contents of an archive and store it in the archive. rar  Create and manage RAR file in Linux. rarpd  Respond to Reverse Address Resoultion Protocol (RARP) requests. rcp  Remote copy command to copy files between remote computers. rdate  Set system date and time by fetching information from a remote machine. rdev  Set or query RAM disk size, image root device, or video mode. rdist  Remote file distribution client, maintains identical file copies over multiple hosts. rdistd  Start the rdist server. read  Read from a file descriptor. readarray  Read lines from a file into an array variable. readcd  Read/write compact disks. readelf  Shows information about ELF (Executable and Linkable fomrat) files. readlink  Display value of a symbolic link or canonical file name. readonly  Mark functions and variables as read-only. reboot  Restart the machine. reject  Accept/reject print jobs sent to a specified destination. remsync  Synchronize remote files over email. rename  Rename one or more files. renice  Change priority of active processes. repquota  Report disk usage and quotas for a specified filesystem. reset  Reinitialize the terminal. resize2fs  Used to resize ext2/ext3/ext4 file systems. restore  Restore files from a backup created using dump. return  Exit a shell function. rev  Show contents of a file, reversing the order of characters in every line. rexec  Remote execution client for exec server. rexecd  Remote execution server. richtext  View “richtext” on an ACSII terminal. rlogin  Used to connect a local host system with a remote host. rlogind  Acts as the server for rlogin. It facilitates remote login, and authentication based on privileged port numbers from trusted hosts. rm  Removes specified files and directories (not by default). rmail  Handle remote mail received via uucp. rmdir  Used to remove empty directories. rmmod  A program to remove modules from Linux kernel. rndc  Name server control utility. Send command to a BIND DNS server over a TCP connection. rootflags  Show/set flags for the kernel image. route  Show/change IP routing table. routed  A daemon, invoked at boot time, to manage internet routing tables. rpcgen  An RPC protocol compiler. Parse a file written in the RPC language. rpcinfo  Shows RPC information. Makes an RPC call to an RPC server and reports the findings. rpm  A package manager for linux distributions. Originally developed for RedHat Linux. rsh  Remote shell. Connects to a specified host and executes commands. rshd  A daemon that acts as a server for rsh and rcp commands. rsync  A versitile to for copying files remotely and locally. runlevel  Shows previous and current SysV runlevel. rup  Remote status display. Shows current system status for all or specified hosts on the local network. ruptime  Shows uptime and login details of the machines on the local network. rusers  Shows the list of the users logged-in to the host or on all machines on the local network. rusersd  The rsuerd daemon acts as a server that responds to the queries from rsuers command. rwall  Sends messages to all users on the local network. rwho  Reports who is logged-in to the hosts on the local network. rwhod  Acts as a server for rwho and ruptime commands. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) S Command Description sane-find-scanner  Find SCSI and USB scanner and determine their device files. scanadf  Retrieve multiple images from a scanner equipped with an automatic document feeder (ADF). scanimage  Read images from image aquistion devices (scanner or camera) and display on standard output in PNM (Portable aNyMap) format. scp  Copy files between hosts on a network securely using SSH. screen  A window manager that enables multiple pseudo-terminals with the help of ANSI/VT100 terminal emulation. script  Used to make a typescript of everything displayed on the screen during a terminal session. sdiff  Shows two files side-by-side and highlights the differences. sed  Stream editor for filtering and transforming text (from a file or a pipe input). select  Synchronous I/O multiplexing. sendmail  It’s a mail router or an MTA (Mail Transfer Agent). sendmail support can send a mail to one or more recepients using necessary protocols. sensors  Shows the current readings of all sensor chips. seq  Displays an incremental sequence of numbers from first to last. set  Used to manipulate shell variables and functions. setfdprm  Sets floppy disk parameters as provided by the user. setkeycodes  Load kernel scancode-to-keycode mapping table entries. setleds  Show/change LED light settings of the keyboard. setmetamode  Define keyboard meta key handling. Without arguments, shows current meta key mode. setquota  Set disk quotas for users and groups. setsid  Run a program in a new session. setterm  Set terminal attributes. sftp  Secure File Transfer program. sh  Command interpreter (shell) utility. sha1sum  Compute and check 160-bit SHA1 checksum to verify file integrity. shift  Shift positional parameters. shopt  Shell options. showkey  Examines codes sent by the keyboard displays them in printable form. showmount  Shows information about NFS server mount on the host. shred  Overwrite a file to hide its content (optionally delete it), making it harder to recover it. shutdown  Power-off the machine. size  Lists section size and the total size of a specified file. skill  Send a signal to processes. slabtop  Show kernel slab cache information in real-time. slattach  Attack a network interface to a serial line. sleep  Suspend execution for a specified amount of time (in seconds). slocate  Display matches by searching filename databases. Takes ownership and file permission into consideration. snice  Reset priority for processes. sort  Sort lines of text files. source  Run commands from a specified file. split  Split a file into pieces of fixed size. ss  Display socket statistics, similar to netstat. ssh  An SSH client for logging in to a remote machine. It provides encrypted communication between the hosts. ssh-add  Adds private key identities to the authentication agent. ssh-agent  It holds private keys used for public key authentication. ssh-keygen  It generates, manages, converts authentication keys for ssh. ssh-keyscan  Gather ssh public keys. sshd  Server for the ssh program. stat  Display file or filesystem status. statd  A daemon that listens for reboot notifications from other hosts, and manages the list of hosts to be notified when the local system reboots. strace  Trace system calls and signals. strfile  Create a random access file for storing strings. strings  Search a specified file and prints any printable strings with at least four characters and followed by an unprintable character. strip  Discard symbols from object files. stty  Change and print terminal line settings. su  Change user ID or become superuser. sudo  Execute a command as superuser. sum  Checksum and count the block in a file. suspend  Suspend the execution of the current shell. swapoff  Disable devices for paging and swapping. swapon  Enable devices for paging and swapping. symlink  Create a symbolic link to a file. sync  Synchronize cached writes to persistent storage. sysctl  Configure kernel parameters at runtime. sysklogd  Linux system logging utilities. Provides syslogd and klogd functionalities. syslogd  Read and log system messages to the system console and log files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) T Command Description tac  Concatenate and print files in reverse order. Opposite of cat command. tail  Show the last 10 lines of each specified file(s). tailf  Follow the growth of a log file. (Deprecated command) talk  A two-way screen-oriented communication utility that allows two user to exchange messages simulateneously. talkd  A remote user communication server for talk . tar  GNU version of the tar archiving utility. Used to store and extract multiple files from a single archive. taskset  Set/retrieve a process’s CPU affinity. tcpd  Access control utility for internet services. tcpdump  Dump traffic on network. Displays a description of the contents of packets on a network interface that match the boolean expression. tcpslice  Extract pieces of tcpdump files or merge them. tee  Read from standard input and write to standard output and files. telinit  Change SysV runlevel. telnet  Telnet protocol user interface. Used to interact with another host using telnet. telnetd  A server for the telnet protocol. test  Check file type and compare values. tftp  User interface to the internet TFTP (Trivial File Transfer Protocol). tftpd  TFTP server. time  Run programs and summarize system resource usage. timeout  Execute a command with a time limit. times  Shows accumulated user and system times for the shell and it’s child processes. tload  Shows a graph of the current system load average to the specified tty. tmpwatch  Recursively remove files and directories which haven’t been accessed for the specified period of time. top  Displays real-time view of processes running on the system. touch  Change file access and modification times. tput  Modify terminal-dependent capabilities, color, etc. tr  Translate, squeeze, or delete characters from standard input and display on standard output. tracepath  Traces path to a network host discovering MTU (Maximum Transmission Unit) along this path. traceroute  Traces the route taken by the packets to reach the network host. trap  Trap function responds to hardware signals. It defines and creates handlers to run when the shell receives signals. troff  The troff processor of the groff text formatting system. TRUE  Exit with a status code indicating success. tset  Initialize terminal. tsort  Perform topological sort. tty  Display the filename of the terminal connected to standard input. tune2fs  Adjust tunable filesystem parameters on ext2/ext3/ext4 filesystems. tunelp  Set various parameters for the line printer devices. type  Write a description for a command type. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) U Command Description ul  Underline text. ulimit  Get and set user limits for the calling process. umask  Set file mode creation mask. umount  Unmount specified file systems. unalias  Remove alias definitions for specified alias names. uname  Show system information. uncompress Uncompress the files compressed with the compress command. unexpand  Convert spaces to tabs for a specified file. unicode_start  Put keyboard and console in Unicode mode. unicode_stop  Revert keyboard and console from Unicode mode. uniq  Report or omit repeating lines. units  Convert units from one scalar to another. unrar  Extract files from a RAR archive. unset  Remove variable or function names. unshar  Unpack shell archive scripts. until  Execute command until a given condition is true. uptime  Tell how long the system has been running. useradd  Create a new user or update default user information. userdel  Delete a user account and related files. usermod  Modify a user account. users  Show the list of active users on the machine. usleep  Suspend execution for microsecond intervals. uudecode  Decode a binary file. uuencode  Encode a binary file. uuidgen  Created a new UUID (Universally Unique Identifier) table. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) V Command Description vdir  Same as ls -l -b . Verbosely list directory contents. vi  A text editor utility. vidmode  Set the video mode for a kernel image. Displays current mode value without arguments. Alternative: rdev -v vim  Vi Improved, a text-based editor which is a successor to vi. vmstat Shows information about processes, memory, paging, block IO, traps, disks, and CPU activity. volname  Returns volume name for a device formatted with an ISO-9660 filesystem. For example, CD-ROM. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) W Command Description w  Show who is logged-on and what they’re doing. wait  Waits for a specified process ID(s) to terminate and returns the termination status. wall  Display a message on the terminals all the users who are currently logged-in. warnquota  Send mail to the users who’ve exceeded their disk quota soft limit. watch  Runs commands repeatedly until interrupted and shows their output and errors. wc  Print newline, word, and byte count for each of the specified files. wget  A non-interactive file download utility. whatis  Display one line manual page descriptions. whereis  Locate the binary, source, and man page files for a command. which  For a given command, lists the pathnames for the files which would be executed when the command runs. while  Conditionally execute commands (while loop). who  Shows who is logged on. whoami  Displays the username tied to the current effective user ID. whois  Looks for an object in a WHOIS database write  Display a message on other user’s terminal. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) X Command Description xargs  Runs a command using initial arguments and then reads remaining arguments from standard input. xdg-open  Used to open a file or URL in an application preferred by the user. xinetd  Extended internet services daemon. Works similar to inetd. xz  Compress/ Decompress .xz and .lzma files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Y Command Description yacc  Yet Another Compiler Compiler, a GNU Project parser generator. yes  Repeatedly output a line with a specified string(s) until killed. ypbind  A daemon that helps client processes to connect to an NIS server. ypcat  Shows the NIS map (or database) for the specified MapName parameter. ypinit  Sets up NIS maps on an NIS server. ypmatch  Shows values for specified keys from an NIS map. yppasswd  Change NIS login password. yppasswdd  Acts as a server for the yppasswd command. Receives and executes requests. yppoll  Shows the ID number or version of NIS map currently used on the NIS server. yppush  Forces slave NIS servers to copy updated NIS maps. ypserv  A daemon activated at system startup. It looks for information in local NIS maps. ypset  Point a client (running ypbind) to a specifc server (running ypserv). yptest  Calls various functions to check the configuration of NIS services. ypwhich  Shows the hostname for NIS server or master server for a given map. ypxfr  Transfers NIS server map from server to a local host. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Z Command Description zcat  Used to compress/uncompress files. Similar to gzip zcmp  Compare compressed files. zdiff  Compare compressed files line by line. zdump  Displays time for the timezone mentioned. zforce  Adds .gz extension to all gzipped files. zgrep  Performs grep on compressed files. zic  Creates time conversion information files using the specified input files. zip  A file compression and packaging utility. zless  Displays information of a compressed file (using less command) on the terminal one screen at a time. zmore  Displays output of a compressed file (using more command) on the terminal one page at a time. znew  Recompress .z files to .gz. files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Quick cheat sheet 📝 >**Note** > Examples like `-a|--all` option flags means, single `-` used for _short_ option(-a) **or**| double `--` used for _long_ option(--all). Both was added for educational purpose.### Contents- [Command Information](#command-information)- [Command History](#command-history)- [Navigating Directories](#navigating-directories)- [Creating Directories](#creating-directories)- [Moving Directories](#moving-directories)- [Deleting Directories](#deleting-directories)- [Creating Files](#creating-files)- [Standard Output, Error and Input](#standard-output-standard-error-and-standard-input)- [Moving Files](#moving-files)- [Deleting Files](#deleting-files)- [Reading Files](#reading-files)- [File Permissions](#file-permissions)- [Finding Files](#finding-files)- [Find in Files](#find-in-files)- [Replace in Files](#replace-in-files)- [Symbolic Links](#symbolic-links)- [Compressing Files](#compressing-files)- [Decompressing Files](#decompressing-files)- [Packages](#packages)- [Disk Usage](#disk-usage)- [Memory Usage](#memory-usage)- [Shutdown and Reboot](#shutdown-and-reboot)- [Identifying Processes](#identifying-processes)- [Process Priority](#process-priority)- [Killing Processes](#killing-processes)- [Date & Time](#date--time)- [Scheduled Tasks](#scheduled-tasks)- [User Mangement](#user-management)- [HTTP Requests](#http-requests)- [Network Troubleshooting](#network-troubleshooting)- [DNS](#dns)- [Hardware](#hardware)- [System Information](#system-information)- [Terminal Multiplexers](#terminal-multiplexers)- [Secure Shell Protocol (SSH)](#secure-shell-protocol-ssh)- [Secure Copy](#secure-copy)- [Bash Profile](#bash-profile)- [Bash Script](#bash-script)### Command Information```bashman chmod # Display page manual of a commandman -f|--whatis chmod # Display short description about a commandman -k|--apropos permission # Display all related commands from a specific keywordchmod --help # Display usage options of a command```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Command History```bashhistory # View all previous commandshistory | grep foo # View the commands using a specific wordhistory | grep -E|--extended-regexp -i|--ignore-case 'foo1|foo2|foo3' # View the commands using more than 1 specific word(case sensitive)history | head -n|--lines 3 # View the first 3 executed commandshistory 3 # View the last 3 executed commandshistory -d 99 # Clear a command from a specific line history -c # Clears all history commands!! # Run the last command executedtouch foo.sh # <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<┐chmod +x !$ # !$ is the last argument of the last command i.e. foo.sh <<<<┘```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Navigating Directories```bashpwd # Print current directory pathls # List directoriesls -a|--all # List directories including hiddenls -l # List directories in long formls -l -h|--human-readable # List directories in long form with human readable sizesls -t # List directories by modification time, newest firststat foo.txt # List size, created and modified timestamps for a filestat foo # List size, created and modified timestamps for a directorytree # List directory and file treetree -a # List directory and file tree including hiddentree -d # List directory treecd foo # Go to foo sub-directorycd # Go to home directorycd ~ # Go to home directorycd - # Go to last directorypushd foo # Go to foo sub-directory and add previous directory to stackpopd # Go back to directory in stack saved by `pushd````[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Creating Directories ```bashmkdir foo # Create a directorymkdir foo bar # Create multiple directoriesmkdir -p|--parents foo/bar # Create nested directorymkdir -p|--parents {foo,bar}/baz # Create multiple nested directoriesmktemp -d|--directory # Create a temporary directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Moving Directories```bashcp -R|--recursive foo bar # Copy directorymv foo bar # Move directoryrsync -z|--compress -v|--verbose /foo /bar # Copy directory, overwrites destinationrsync --ignore-existing -a|--archive-a|--archive -z|--compress -v|--verbose /foo /bar # Copy directory, without overwriting destinationrsync -avz /foo username@hostname:/bar # Copy local directory to remote directoryrsync -avz username@hostname:/foo /bar # Copy remote directory to local directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Deleting Directories```bashrmdir foo # Delete non-empty directoryrm -r|--recursive foo # Delete directory including contentsrm -r|--recursive -f|--force foo # Delete directory including contents, ignore nonexistent files and never prompt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Creating Files```bashtouch foo.txt # Create file or update existing files modified timestamptouch foo.txt bar.txt # Create multiple filestouch {foo,bar}.txt # Create multiple filestouch test{1..3} # Create test1, test2 and test3 filestouch test{a..c} # Create testa, testb and testc filesmktemp # Create a temporary file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Standard Output, Standard Error and Standard Input```bashecho "foo" > bar.txt # Overwrite file with contentecho "foo" >> bar.txt # Append to file with contentls exists 1> stdout.txt # Redirect the standard output to a filels noexist 2> stderror.txt # Redirect the standard error output to a filels > out.txt 2>&1 # Redirect standard output and error to a filels > /dev/null # Discard standard output and errorread foo # Read from standard input and write to the variable foo```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Moving Files```bashcp foo.txt bar.txt # Copy filemv foo.txt bar.txt # Move filersync -z|--compress -v|--verbose /foo.txt /bar # Copy file quickly if not changedrsync -z|--compress -v|--verbose /foo.txt /bar.txt # Copy and rename file quickly if not changed```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Deleting Files```bashrm foo.txt # Delete filerm -f|--force foo.txt # Delete file, ignore nonexistent files and never prompt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Reading Files```bashcat foo.txt # Print all contentsless foo.txt # Print some contents at a time (g - go to top of file, SHIFT+g, go to bottom of file, /foo to search for 'foo')head foo.txt # Print top 10 lines of filetail foo.txt # Print bottom 10 lines of fileopen foo.txt # Open file in the default editorwc foo.txt # List number of lines words and characters in the file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## File Permissions| # | Permission | rwx | Binary || - | - | - | - || 7 | read, write and execute | rwx | 111 || 6 | read and write | rw- | 110 || 5 | read and execute | r-x | 101 || 4 | read only | r-- | 100 || 3 | write and execute | -wx | 011 || 2 | write only | -w- | 010 || 1 | execute only | --x | 001 || 0 | none | --- | 000 |For a directory, execute means you can enter a directory.| User | Group | Others | Description || - | - | - | - || 6 | 4 | 4 | User can read and write, everyone else can read (Default file permissions) || 7 | 5 | 5 | User can read, write and execute, everyone else can read and execute (Default directory permissions) |- u - User- g - Group- o - Others- a - All of the above```bashls -l /foo.sh # List file permissionschmod +100 foo.sh # Add 1 to the user permissionchmod -100 foo.sh # Subtract 1 from the user permissionchmod u+x foo.sh # Give the user execute permissionchmod g+x foo.sh # Give the group execute permissionchmod u-x,g-x foo.sh # Take away the user and group execute permissionchmod u+x,g+x,o+x foo.sh # Give everybody execute permissionchmod a+x foo.sh # Give everybody execute permissionchmod +x foo.sh # Give everybody execute permission```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Finding FilesFind binary files for a command.```bashtype -a wget # Display all locations of executablewhich -a wget # Display all locations of executables whereis wget # Find the binary, source, and manual page files````locate` uses an index and is fast.```bashupdatedb # Update the indexlocate foo.txt # Find a filelocate --ignore-case # Find a file and ignore caselocate f*.txt # Find a text file starting with 'f'````find` doesn't use an index and is slow.```bashfind /path -name foo.txt # Find a filefind /path -iname foo.txt # Find a file with case insensitive searchfind /path -name "*.txt" # Find all text filesfind /path -name foo.txt -delete # Find a file and delete itfind /path -name "*.png" -exec pngquant {} # Find all .png files and execute pngquant on itfind /path -type f -name foo.txt # Find a filefind /path -type d -name foo # Find a directoryfind /path -type l -name foo.txt # Find a symbolic linkfind /path -type f -mtime +30 # Find files that haven't been modified in 30 daysfind /path -type f -mtime +30 -delete # Delete files that haven't been modified in 30 days```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Find in Files```bashgrep 'foo' /bar.txt # Search for 'foo' in file 'bar.txt'grep 'foo' /bar -r|--recursive # Search for 'foo' in directory 'bar'grep 'foo' /bar -R|--dereference-recursive # Search for 'foo' in directory 'bar' and follow symbolic linksgrep 'foo' /bar -l|--files-with-matches # Show only files that matchgrep 'foo' /bar -L|--files-without-match # Show only files that don't matchgrep 'Foo' /bar -i|--ignore-case # Case insensitive searchgrep 'foo' /bar -x|--line-regexp # Match the entire linegrep 'foo' /bar -C|--context 1 # Add N line of context above and below each search resultgrep 'foo' /bar -v|--invert-match # Show only lines that don't matchgrep 'foo' /bar -c|--count # Count the number lines that matchgrep 'foo' /bar -n|--line-number # Add line numbersgrep 'foo' /bar --colour # Add colour to outputgrep 'foo\|bar' /baz -R # Search for 'foo' or 'bar' in directory 'baz'grep --extended-regexp|-E 'foo|bar' /baz -R # Use regular expressionsgrep -E 'foo|bar' /baz -R # Use regular expressions```### Replace in Files```bashsed 's/fox/bear/g' foo.txt # Replace fox with bear in foo.txt and output to consolesed 's/fox/bear/gi' foo.txt # Replace fox (case insensitive) with bear in foo.txt and output to consolesed 's/red fox/blue bear/g' foo.txt # Replace red with blue and fox with bear in foo.txt and output to consolesed 's/fox/bear/g' foo.txt > bar.txt # Replace fox with bear in foo.txt and save in bar.txtsed 's/fox/bear/g' foo.txt -i|--in-place # Replace fox with bear and overwrite foo.txt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Symbolic Links```bashln -s|--symbolic foo bar # Create a link 'bar' to the 'foo' folderln -s|--symbolic -f|--force foo bar # Overwrite an existing symbolic link 'bar'ls -l # Show where symbolic links are pointing```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Compressing Files### zipCompresses one or more files into *.zip files.```bashzip foo.zip /bar.txt # Compress bar.txt into foo.zipzip foo.zip /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.zipzip foo.zip /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.zipzip -r|--recurse-paths foo.zip /bar # Compress directory bar into foo.zip```### gzipCompresses a single file into *.gz files.```bashgzip /bar.txt foo.gz # Compress bar.txt into foo.gz and then delete bar.txtgzip -k|--keep /bar.txt foo.gz # Compress bar.txt into foo.gz```### tar -cCompresses (optionally) and combines one or more files into a single *.tar, *.tar.gz, *.tpz or *.tgz file.```bashtar -c|--create -z|--gzip -f|--file=foo.tgz /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.tgztar -c|--create -z|--gzip -f|--file=foo.tgz /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.tgztar -c|--create -z|--gzip -f|--file=foo.tgz /bar # Compress directory bar into foo.tgz```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Decompressing Files### unzip```bashunzip foo.zip # Unzip foo.zip into current directory```### gunzip```bashgunzip foo.gz # Unzip foo.gz into current directory and delete foo.gzgunzip -k|--keep foo.gz # Unzip foo.gz into current directory```### tar -x```bashtar -x|--extract -z|--gzip -f|--file=foo.tar.gz # Un-compress foo.tar.gz into current directorytar -x|--extract -f|--file=foo.tar # Un-combine foo.tar into current directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Packages```bashapt update # Refreshes repository indexapt search wget # Search for a packageapt show wget # List information about the wget packageapt list --all-versions wget # List all versions of the packageapt install wget # Install the latest version of the wget packageapt install wget=1.2.3 # Install a specific version of the wget packageapt remove wget # Removes the wget packageapt upgrade # Upgrades all upgradable packagesapt clean # Clears out the local repository of downloaded package filesdpkg -i|--install package_name.deb # Install deb filerpm -i|--install package_name.rpm # Install rpm file ```### Install package source code```bashtar zxvf sourcecode.tar.gzcd sourcecode./configuremakemake install```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Disk Usage```bashdf # List disks, size, used and available spacedf -h|--human-readable # List disks, size, used and available space in a human readable formatdu # List current directory, subdirectories and file sizesdu /foo/bar # List specified directory, subdirectories and file sizesdu -h|--human-readable # List current directory, subdirectories and file sizes in a human readable formatdu -d|--max-depth # List current directory, subdirectories and file sizes within the max depthdu -d 0 # List current directory size```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Memory Usage```bashfree # Show memory usagefree -h|--human # Show human readable memory usagefree -h|--human --si # Show human readable memory usage in power of 1000 instead of 1024free -s|--seconds 5 # Show memory usage and update continuously every five seconds```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Shutdown and Reboot```bashshutdown # Shutdown in 1 minuteshutdown now # Immediately shut downshutdown +5 # Shutdown in 5 minutesshutdown -r|--reboot # Reboot in 1 minuteshutdown -r|--reboot now # Immediately rebootshutdown -r|--reboot +5 # Reboot in 5 minutesshutdown -c # Cancel a shutdown or rebootreboot # Reboot nowreboot -f # Force a reboot```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Identifying Processes```bashtop # List all processes interactivelyhtop # List all processes interactivelyps ax # List all processespidof foo # Return the PID of all foo processesCTRL+Z # Suspend a process running in the foregroundbg # Resume a suspended process and run in the backgroundfg # Bring the last background process to the foregroundfg 1 # Bring the background process with the PID to the foregroundsleep 30 & # Sleep for 30 seconds and move the process into the backgroundjobs # List all background jobsjobs -p # List all background jobs with their PIDlsof # List all open files and the process using themlsof -itcp:4000 # Return the process listening on port 4000```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Process PriorityProcess priorities go from -20 (highest) to 19 (lowest).```bashnice -n -20 foo # Change process priority by namerenice 20 PID # Change process priority by PIDps -o ni PID # Return the process priority of PID```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Killing Processes```bashCTRL+C # Kill a process running in the foregroundkill PID # Shut down process by PID gracefully. Sends TERM signal.kill -9 PID # Force shut down of process by PID. Sends SIGKILL signal.pkill foo # Shut down process by name gracefully. Sends TERM signal.pkill -9 foo # force shut down process by name. Sends SIGKILL signal.killall foo # Kill all process with the specified name gracefully.```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Date & Time```bashdate # Print the date and timedate --iso-8601 # Print the ISO8601 datedate --iso-8601=ns # Print the ISO8601 date and timedate -s "02 DEC 2020 12:02:02" # Manually change date and timedpkg-reconfigure tzdata # Change date/timezoneuptime # Print how long the system has been runningtime tree # Print amount of time to tree takes to execute```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Scheduled Tasks```pre * * * * *Minute, Hour, Day of month, Month, Day of the week``````bashcrontab -l # List cron tabcrontab -e # Edit cron tab in Vimcrontab /path/crontab # Load cron tab from a filecrontab -l > /path/crontab # Save cron tab to a file* * * * * foo # Run foo every minute*/15 * * * * foo # Run foo every 15 minutes0 * * * * foo # Run foo every hour15 6 * * * foo # Run foo daily at 6:15 AM44 4 * * 5 foo # Run foo every Friday at 4:44 AM0 0 1 * * foo # Run foo at midnight on the first of the month0 0 1 1 * foo # Run foo at midnight on the first of the yearat -l # List scheduled tasksat -c 1 # Show task with ID 1at -r 1 # Remove task with ID 1at now + 2 minutes # Create a task in Vim to execute in 2 minutesat 12:34 PM next month # Create a task in Vim to execute at 12:34 PM next monthat tomorrow # Create a task in Vim to execute tomorrow```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## User Management```bashadduser username # To add a new userpasswd -l|--lock username # To change the password of a useruserdel username # To remove useruserdel -r|--remove username # To remove user with home directory and mail spoolusermod -a|--append -G|--groups GROUPNAME USERNAME # To add a user to a groupdeluser USER GROUPNAME # To remove a user from a grouplast # Shows information of all the users logged inlast username # Gives information of a particular user```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## HTTP Requests```bashcurl https://example.com # Return response bodycurl -i|--include https://example.com # Include status code and HTTP headerscurl -L|--location https://example.com # Follow redirectscurl -O|--remote-name foo.txt https://example.com # Output to a text filecurl -H|--header "User-Agent: Foo" https://example.com # Add a HTTP headercurl -X|--request POST -H "Content-Type: application/json" -d|--data '{"foo":"bar"}' https://example.com # POST JSONcurl -X POST -H --data-urlencode foo="bar" http://example.com # POST URL Form Encodedwget https://example.com/file.txt # Download a file to the current directorywget -O|--output-document foo.txt https://example.com/file.txt # Output to a file with the specified name```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Network Troubleshooting```bashping example.com # Send multiple ping requests using the ICMP protocolping -c 10 -i 5 example.com # Make 10 attempts, 5 seconds apartip addr # List IP addresses on the systemip route show # Show IP addresses to routercurl ifconfig.me # Obtain external IP addressnetstat -i|--interfaces # List all network interfaces and in/out usagenetstat -l|--listening # List all open portstraceroute example.com # List all servers the network traffic goes throughmtr -w|--report-wide example.com # Continually list all servers the network traffic goes throughmtr -r|--report -w|--report-wide -c|--report-cycles 100 example.com # Output a report that lists network traffic 100 timesnmap 0.0.0.0 # Scan for the 1000 most common open ports on localhostnmap 0.0.0.0 -p1-65535 # Scan for open ports on localhost between 1 and 65535nmap 192.168.4.3 # Scan for the 1000 most common open ports on a remote IP addressnmap -sP 192.168.1.1/24 # Discover all machines on the network by ping'ing them```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## DNS```bashdig example.com # Show query information of domain A recordsdig -4 example.com # Show IPv4 A recordsdig -6 example.com # Show IPv6 AAA recordsdig example.com @nameserver # Show query of a specific nameserverdig example.com -p 123 # Show query of a specific port numbercat /etc/resolv.conf # Nameservers filecat /etc/systemd/resolved.conf # DNS resolver config file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Hardware```bashlsusb # List USB deviceslspci # List PCI hardwarelshw # List all hardware```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## System Information```uname -s # Print kernel nameuname -r # Print kernel releaseuname -m # Print Architectureuname -o # Print Operating System```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Terminal MultiplexersStart multiple terminal sessions. Active sessions persist reboots. `tmux` is more modern than `screen`.```bashtmux # Start a new session (CTRL-b + d to detach)tmux ls # List all sessionstmux attach -t 0 # Reattach to a sessionscreen # Start a new session (CTRL-a + d to detach)screen -ls # List all sessionsscreen -R 31166 # Reattach to a sessionexit # Exit a session```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Secure Shell Protocol (SSH)```bashssh hostname # Connect to hostname using your current user name over the default SSH port 22ssh -i foo.pem hostname # Connect to hostname using the identity filessh user@hostname # Connect to hostname using the user over the default SSH port 22ssh user@hostname -p 8765 # Connect to hostname using the user over a custom portssh ssh://user@hostname:8765 # Connect to hostname using the user over a custom port```Set default user and port in `~/.ssh/config`, so you can just enter the name next time:```bash$ cat ~/.ssh/configHost name User foo Hostname 127.0.0.1 Port 8765$ ssh name```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Secure Copy```bashscp foo.txt ubuntu@hostname:/home/ubuntu # Copy foo.txt into the specified remote directoryscp ubuntu@hostname:/home/ubuntu/foo.txt /C:\Users\Admin # Copy foo.txt from the specified remote directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Bash Profile- bash - `.bashrc`- zsh - `.zshrc````bash# Always run ls after cdfunction cd { builtin cd "$@" && ls}# Prompt user before overwriting any filesalias cp='cp --interactive'alias mv='mv --interactive'alias rm='rm --interactive'# Always show disk usage in a human readable formatalias df='df -h'alias du='du -h'```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Bash Script### Variables```bash#!/bin/bashfoo=123 # Initialize variable foo with 123declare -i foo=123 # Initialize an integer foo with 123declare -r foo=123 # Initialize readonly variable foo with 123echo $foo # Print variable fooecho ${foo}_'bar' # Print variable foo followed by _barecho ${foo:-'default'} # Print variable foo if it exists otherwise print defaultexport foo # Make foo available to child processesunset foo # Make foo unavailable to child processes and current session```### Environment Variables```bash#!/bin/bashset # List all environment variablesecho $PATH # Print PATH environment variableexport FOO=Bar # Set an environment variable```### Functions```bash#!/bin/bashgreet() { local world="World" echo "$1 $world" return "$1 $world"}greet "Hello"greeting=$(greet "Hello")```### Exit Codes```bash#!/bin/bashexit 0 # Exit the script successfullyexit 1 # Exit the script unsuccessfullyecho $? # Print the last exit code```### Conditional Statements#### Boolean Operators- `$foo` - Is true- `!$foo` - Is false#### Numeric Operators- `-eq` - Equals- `-ne` - Not equals- `-gt` - Greater than- `-ge` - Greater than or equal to- `-lt` - Less than- `-le` - Less than or equal to- `-e` foo.txt - Check file exists- `-z` foo - Check if variable exists#### String Operators- `=` - Equals- `==` - Equals- `-z` - Is null- `-n` - Is not null- `<` - Is less than in ASCII alphabetical order- `>` - Is greater than in ASCII alphabetical order#### If Statements```bash#!/bin/bash[[if [[$foo = 'bar']]; then echo 'one'elif [[$foo = 'bar']] || [[$foo = 'baz']]; then echo 'two'elif [[$foo = 'ban']] && [[$USER = 'bat']]; then echo 'three'else echo 'four'fi]]```#### Inline If Statements```bash#!/bin/bash[[ $USER = 'rehan' ]] && echo 'yes' || echo 'no'```#### While Loops```bash#!/bin/bash[declare -i countercounter=10while [$counter -gt 2]; do echo The counter is $counter counter=counter-1done]```#### For Loops```bash#!/bin/bashfor i in {0..10..2} do echo "Index: $i" donefor filename in file1 file2 file3 do echo "Content: " >> $filename donefor filename in *; do echo "Content: " >> $filename done```#### Case Statements```bash#!/bin/bashecho "What's the weather like tomorrow?"read weathercase $weather in sunny | warm ) echo "Nice weather: " $weather ;; cloudy | cool ) echo "Not bad weather: " $weather ;; rainy | cold ) echo "Terrible weather: " $weather ;; * ) echo "Don't understand" ;;esac```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents) Special characters 🔣 Char. Description ~  Home directory [tilde]. The current user's home directory location /  Filename path separator [forward slash]. Separates the components of a filename \  Escape [backslash]. A quoting mechanism for single characters. \X escapes the character X. It preserves the literal value of the next character that follows, with the exception of newline │  Pipe. It passes the output (stdout) of a previous command to the input (stdin) of the next one, or to the shell. This is a method of chaining commands together ||  OR logical operator causes a return of 0 (success) if either of the linked test conditions is true &&  AND logical operator causes a return of 0 (success) only if both the linked test conditions are true -  Option flag for a command or filter. The default parameter in parameter substitution --  The double-dash prefixes is the long (verbatim) option flags for commands >, >>, <  Redirect a command's output or input into a file >|  Force redirection (even if the noclobber option is set). This will forcibly overwrite an existing file &  Run job in background. A command followed by an & will run in the background "  Partial quoting [double quote]. "STRING" preserves (from interpretation) most of the special characters within STRING '  Full quoting [single quote]. 'STRING' preserves all special characters within STRING. This is a stronger form of quoting than "STRING" ' '  Single quotes. Protect the text inside them so that it has a literal meaning ""  Double quotes protect the text inside them from being split into multiple words or arguments, yet allow substitutions to occur, meaning most other special characters is usually prevented " "  Whitespace. This is a tab, newline, vertical tab, form feed, carriage return, or space. Bash uses whitespace to determine where words begin and end ;  Command separator [semicolon]. Used to separate multiple commands that are on the same line :  Null command [colon]. This is the shell equivalent of a "NOP" (no op, a do-nothing operation). It may be considered a synonym for the shell builtin true !  Reverse (or negate) [exclamation]. The ! operator inverts the exit status of the command to which it is applied. It also inverts the meaning of a test operator *  Wild card [asterisk]. Glob , "wildcard" characters which match parts of filenames (e.g. ls *.txt) { }  Inline group [curly brackets]. Commands inside the curly braces are treated as if they were one command. It is convenient to use these when Bash syntax requires only one command and a function doesn't feel warranted ( )   Subshell group [bracket].Commands within are executed in a subshell (a new process) Used much like a sandbox, if a command causes side effects (like changing variables), it will have no effect on the current shell [ ]  Test expression between [ ]. Is part of the shell builtin test [[ ]]  Test expression between [[ ]]. More flexible than the single-bracket [ ] test (( ))  Integer expansion. Expand and evaluate integer expression between (( )) ;;  Terminator in a case option [double semicolon] ;;&, ;&  Terminators in a case option ,, ,  Lowercase conversion in parameter substitution ?  Test operator[question mark]. Within certain expressions, the ? indicates a test for a condition #  Comment [number sign]. Lines in files beginning with a # (with the exception of #!) are comments and will not be executed Keyboard control ⌨️ | Key | Function || :--: | :-- || Ctrl+a | Moves cursor to beginning of text in line || Ctrl+e | Moves cursor to end of text in line || Ctrl+b | Moves cursor backward one character position || Ctrl+f | Moves cursor forward one character position || Ctrl+p | Fetch previous command from history buffer || Ctrl+n | Fetch next command from history buffer || Ctrl+r | Reverse search commands in history buffer || Ctrl+u | Erase a line of input from cursor right to left of line || Ctrl+k | Erase a line of input from cursor left to right of line || Ctrl+y | Fetch back command previously erased || Ctrl+t | Reverses the position of the character the cursor is on with the previous character || Ctrl+z | Pauses a foreground job || Ctrl+c | Break/Terminate a foreground job || Ctrl+o | Accept the current line for execution and fetch the next command || Ctrl+l | Clear screen || Ctrl+s | Suspend || Ctrl+q | Resume || Ctrl+d | Log out from a shell (similar to exit) | Online Cheat Sheet :feelsgood: for quick references of commands and codes cheat.sh Terminal:```bashcurl cht.sh/keyword or curl cheat.sh/keyword```Browser: https://cht.sh/ keyword https://cheat.sh/ keyword # Install cheat script manually for offline usage ```bash Install for all users: curl -s https://cht.sh/:cht.sh | sudo tee /usr/local/bin/cht.sh && sudo chmod +x /usr/local/bin/cht.sh Run script: cht.sh ``` To restore the repository download the bundle wget https://archive.org/download/github.com-trinib-Linux-Bash-Commands_-_2022-11-07_04-40-19/trinib-Linux-Bash-Commands_-_2022-11-07_04-40-19.bundle and run: git clone trinib-Linux-Bash-Commands_-_2022-11-07_04-40-19.bundle Source: https://github.com/trinib/Linux-Bash-Commands Uploader: trinib Upload date: 2022-11-07

Summary: You need this information to understand your system better Source: http://hackerpublicradio.org/eps.php?id=3878 Original audio: https://archive.org/download/hpr3878/hpr3878_source.mp3 https://www.redhat.com/sysadmin/linux-system-info-commands The various ls commands lscpu, lsblk, lspci, The disk commands df, fdisk and mount Usbutils pciutils Free dmidecode -t memory or -t bios or -t system

This is a cheat sheet of some of the basic Linux commands for file management, text processing, package management, etc. It was created for the third meeting in the Introduction to Linux trilogy available here .

This is a cheat sheet of some of the basic Linux commands for file management, text processing, package management, etc. It was created for the third meeting in the Introduction to Linux trilogy available here .

This is a tutorial for basic LINUX Commands using the command line. Uploaded into the Public Domian under the Creative Commons License by Gerard Arthus.

Introduction To Linux File System Commands by Andy Sayler; uploaded by Gerard Arthus into the Public Domain under the Creative Commons License. Published on Oct 31, 2012 Introduction to Linux Session 2 Part 1 - "File System Commands" 10/30/2012 Next Part: http://youtu.be/rmFXUewy6gA Previous Part: http://youtu.be/i5nitS8KF3o Sponsored by: The Aerospace Graduate Student Organization (AGSO) Department of Aerospace Engineering Sciences University of Colorado, Boulder Taught By: Andy Sayler www.andysayler.com Matt Monaco [email protected]

Hardcore computing. No #GUI just commands. And I don't remember how to get back to windows so - the challenge is on #FreeBSD #Linux #VMware -eJduemWqqUi

This week we are checking out more expansion commands with nesting and parameters.

Linux MAC Windows OS Commands

:godmode: Ultimate list of Linux bash commands # Ultimate list of Linux bash commands_Bash is the [Unix](https://www.google.com/search?q=What+is+UNIX+explain%3F&client=firefox-b-d&sxsrf=ALiCzsZmYtgn9ctD5vHAqgVFkM5tZ514pw%3A1667926333803&ei=PYlqY6XIMNmNwbkPqeK3qAo&ved=0ahUKEwjl2ozlhZ_7AhXZRjABHSnxDaUQ4dUDCA4&uact=5&oq=What+is+UNIX+explain%3F&gs_lcp=Cgxnd3Mtd2l6LXNlcnAQAzIFCAAQgAQyBQgAEIAEMgUIABCABDIGCAAQFhAeMgYIABAWEB4yBggAEBYQHjIFCAAQhgMyBQgAEIYDMgUIABCGAzIFCAAQhgM6CggAEEcQ1gQQsAM6BwgAELADEENKBAhNGAFKBAhBGABKBAhGGABQnAFYnAFgvwNoAXABeACAAa0BiAGtAZIBAzAuMZgBAKABAqABAcgBCsABAQ&sclient=gws-wiz-serp) command-line interface (CLI). Also called the terminal, the command line, or the shell. It's a command language that allows us to work with files on our computers in a way that's far more efficient and powerful than using a GUI (graphical user interface)_ A to Z command list 📚 > **Note** > Use `Ctrl+f` to search in browsers🔎 Table #### │ [A](#-a) │ [B](#-b) │ [C](#-c) │ [D](#-d) │ [E](#-e) │ [F](#-f) │ [G](#-g) │ [H](#-h) │ [I](#-i) │ [J](#-j) │ [K](#-k) │ [L](#-l) │ [M](#-m) │ [N](#-n) │ [O](#-o) │ [P](#-p) │ [Q](#-q) │ [R](#-r) │ [S](#-s) │ [T](#-t) │ [U](#-u) │ [V](#-v) │ [W](#-w) │ [X](#-x) │ [Y](#-y) │ [Z](#-z) │ A Command Description accept Accept or Reject jobs to a destination, such as a printer. access Check a user’s RWX(read, write and execute) permission for a file. accton Used to turn on or turn off the process for accounting or change info process accounting file. aclocal Used to automatically generate aclocal.m4 files from configure.in file. aconnect ALSA(Advanced Linux Sound Architecture) sequencer connection manager. acpi Show information about the Advanced Configuration and Power Interface. acpi_available Check if ACPI(Advanced Configuration and Power Interface) functionality exists on the system. acpid Informs user-space programs about ACPI events. addr2line Used to convert addresses into file names and line numbers. addresses Formats for internet mail addresses. agetty An alternative Linux Getty that manages physical or virtual terminals to allow multi-user access alias Create an alias, a shortcut that references a command. alsactl Access advanced controls for ALSA soundcard driver. amidi Perform read/write operation for ALSA RawMIDI ports. amixer Access CLI-based mixer for ALSA soundcard driver. anacron Used to run commands periodically. aplay Sound recorder and player for CLI. aplaymidi CLI utility used to play MIDI files. apm Show Advanced Power Management (APM) hardware info on older systems. apmd Used to handle events reported by APM BIOS drivers. apropos Shows the list of all man pages containing a specific keyword. apt Advanced Package Tool, a package management system for Debian and derivatives. apt-get Command-line utility to install/remove/update packages based on APT system. aptitude Another utility to add/remove/upgrade packages based on the APT system. ar A utility to create/modify/extract from archives. arch Display print machine hardware name. arecord Just like aplay, it’s a sound recorder and player for ALSA soundcard driver. arecordmidi Record standard MIDI files. arp Used to make changes to the system’s ARP cache. as A portable GNU assembler. aspell An interactive spell checker utility. at Used to schedule command execution at specified date & time, reading commands from an input file. atd Used to execute jobs queued by the at command. atq List a user’s pending jobs for the at command. atrm Delete jobs queued by the at command. audiosend Used to send an audio recording as an email. aumix An audio mixer utility. autoconf Generate configuration scripts from a TEMPLATE-FILE and send the output to standard output. autoheader Create a template header for configure. automake Creates GNU standards-compliant Makefiles from template files. autoreconf Update generated configuration files. autoscan Generate a preliminary configure.in file. autoupdate Update a configure.in file to newer autoconf. awk A scripting language used for manipulating data and generating reports. Also used to find and replace text in a file(s). [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) B Command Description badblocks Search a disk partition for bad sectors. banner Used to print characters as a poster. basename Used to display filenames with directory or suffix. bash GNU Bourne-Again Shell. batch Used to run commands entered on a standard input. bc Access the GNU bc calculator utility. bg Send processes to the background. biff Notify about incoming mail and sender’s name on a system running comsat server. bind Used to attach a name to a socket. bison A GNU parser generator, compatible with yacc. break Used to exit from a loop (eg: for, while, select). builtin Used to run shell builtin commands, make custom functions for commands extending their functionality. bzcmp Used to call the cmp program forbzip2 compressed files. bzdiff Used to call the diff program for bzip2 compressed files. bzgrep Used to call grep for bzip2 compressed files. bzip2 A block-sorting file compressor used to shrink given files. bzless Used to apply ‘less’ (show info one page at a time) to bzip2 compressed files. bzmore Used to apply ‘more’ (an inferior version of less) to bzip2 compressed files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) C Command Description cal Show calendar. cardctl Used to control PCMCIA sockets and select configuration schemes. cardmgr Keeps an eye on the added/removes sockets for PCMCIA devices. case Execute a command conditionally by matching a pattern. cat Used to concatenate files and print them on the screen. cc GNU C and C++ compiler. ccrypt Used for encryption and decryption of data. cd Used to change directory. cdda2wav Used to rip a CD-ROM and make WAV file. cdparanoia Record audio from CD more reliably using data-verification algorithms. cdrdao Used to write all the content specified to a file to a CD all at once. cdrecord Used to record data or audio compact discs. cfdisk Show or change the disk partition table. chage Used to change user password information. chattr Used to change file attributes. chdir Used to change active working directory. chfn Used to change real user name and information. chgrp Used to change group ownership for file. chkconfig Manage execution of runlevel services. chmod Change access permission for a file(s). chown Change the owner or group for a file. chpasswd Update password in a batch. chroot Run a command with root directory. chrt Alter process attributed in real-time. chsh Switch login shell. chvt Change foreground virtual terminal. cksum Perform a CRC checksum for files. clear Used to clear the terminal window. cmp Compare two files (byte by byte). col Filter reverse (and half-reverse) line feeds from the input. colcrt Filter nroff output for CRT previewing. colrm Remove columns from the lines of a file. column A utility that formats its input into columns. comm Used to compare two sorted files line by line. command Used to execute a command with arguments ignoring shell function named command. compress Used to compress one or more file(s) and replacing the originals ones. continue Resume the next iteration of a loop. cp Copy contents of one file to another. cpio Copy files from and to archives. cpp GNU C language processor. cron A daemon to execute scheduled commands. crond Same work as cron. crontab Manage crontab files (containing schedules commands) for users. csplit Split a file into sections on the basis of context lines. ctags Make a list of functions and macro names defined in a programming source file. cupsd A scheduler for CUPS. curl Used to transfer data from or to a server using supported protocols. cut Used to remove sections from each line of a file(s). cvs Concurrent Versions System. Used to track file versions, allow storage/retrieval of previous versions, and enables multiple users to work on the same file. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) D Command Description date Show system date and time. dc Desk calculator utility. dd Used to convert and copy a file, create disk clone, write disk headers, etc. ddrescue Used to recover data from a crashed partition. deallocvt Deallocates kernel memory for unused virtual consoles. debugfs File system debugger for ext2/ext3/ext4 declare Used to declare variables and assign attributes. depmod Generate modules.dep and map files. devdump Interactively displays the contents of device or file system ISO. df Show disk usage. diff Used to compare files line by line. diff3 Compare three files line by line. dig Domain Information Groper, a DNS lookup utility. dir List the contents of a directory. dircolors Set colors for ‘ls’ by altering the LS_COLORS environment variable. dirname Display pathname after removing the last slash and characters thereafter. dirs Show the list of remembered directories. disable Restrict access to a printer. dlpsh Interactive Desktop Link Protocol (DLP) shell for PalmOS. dmesg Examine and control the kernel ring buffer. dmidecode Used when the user wants to retrieve system’s hardware related information such as Processor, RAM(DIMMs), BIOS detail, etc. of Linux system in a readable format. dnsdomainname Show the DNS domain name of the system. dnssec-keygen Generate encrypted Secure DNS keys for a given domain name. dnssec-makekeyset Produce domain key set from one or more DNS security keys generated by dnssec-keygen. dnssec-signkey Sign a secure DNS keyset with key signatures specified in the list of key-identifiers. dnssec-signzone Sign a secure DNS zonefile with the signatures in the specified list of key-identifiers. doexec Used to run an executable with an arbitrary argv list provided. domainname Show or set the name of current NIS (Network Information Services) domain. dosfsck Used to retrieve information or statistics form components of the system such as network connections, IO devices, or CPU, etc. dstat Check and repair MS-DOS file systems. du Show disk usage summary for a file(s). dump Backup utility for ext2/ext3 file systems. dumpe2fs Dump ext2/ext3/ext4 file systems. dumpkeys Show information about the keyboard driver’s current translation tables. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) E Command Description e2fsck Used to check ext2/ext3/ext4 file systems. e2image Store important ext2/ext3/ext4 filesystem metadata to a file. e2label Show or change the label on an ext2/ext3/ext4 filesystem. echo Send input string(s) to standard output i.e. display text on the screen. ed GNU Ed – a line-oriented text editor. edquota Used to edit filesystem quotas using a text editor, such as vi. egrep Search and display text matching a pattern. eject Eject removable media. elvtune Used to set latency in the elevator algorithm used to schedule I/O activities for specified block devices. emacs Emacs text editor command line utility. enable Used to enable/disable shell builtin commands. env Run a command in a modified environment. Show/set/delete environment variables. envsubst Substitute environment variable values in shell format strings. esd Start the Enlightenment Sound Daemon (EsounD or esd). Enables multiple applications to access the same audio device simultaneously. esd-config Manage EsounD configuration. esdcat Use EsounD to send audio data from a specified file. esdctl EsounD control program. esddsp Used to reroute non-esd audio data to esd and control all the audio using esd. esdmon Used to copy the sound being sent to a device. Also, send it to a secondary device. esdplay Use EsounD system to play a file. esdrec Use EsounD to record audio to a specified file. esdsample Sample audio using esd. etags Used to create a list of functions and macros from a programming source file. These etags are used by emacs. For vi, use ctags. ethtool Used to query and control network driver and hardware settings. eval Used to evaluate multiple commands or arguments are once. ex Interactive command exec An interactive line-based text editor. exit Exit from the terminal. expand Convert tabs into spaces in a given file and show the output. expect An extension to the Tcl script, it’s used to automate interaction with other applications based on their expected output. export Used to set an environment variable. expr Evaluate expressions and display them on standard output. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) F Command Description factor Display prime factors of specified integer numbers. false Do nothing, unsuccessfully. Exit with a status code indicating failure. fc Used to list, edit or re-execute the commands previously entered into an interactive shell. fc-cache Make font information cache after scanning the directories. fc-list Show the list of available fonts. fdformat Do a low-level format on a floppy disk. fdisk Make changes to the disk partition table. fetchmail Fetch mail from mail servers and forward it to the local mail delivery system. fg Used to send a job to the foreground. fgconsole Display the number of the current virtual console. fgrep Display lines from a file(s) that match a specified string. A variant of grep. file Determine file type for a file. find Do a file search in a directory hierarchy. finger Display user data including the information listed in .plan and .project in each user’s home directory. fingerd Provides a network interface for the finger program. flex Generate programs that perform pattern-matching on text. fmt Used to convert text to a specified width by filling lines and removing new lines, displaying the output. fold Wrap input line to fit in a specified width. for Expand words and run commands for each one in the resultant list. formail Used to filter standard input into mailbox format. format Used to format disks. free Show free and used system memory. fsck Check and repair a Linux file system ftp File transfer protocol user interface. ftpd FTP server process. function Used to define function macros. Fun Used to draw various type of patterns on the terminal. fuser Find and kill a process accessing a file. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) G Command Description g++ Run the g++ compiler. gawk Used for pattern scanning and language processing. A GNU implementation of AWK language. gcc A C and C++ compiler by GNU. gdb A utility to debug programs and know about where it crashes. getent Shows entries from Name Service Switch Libraries for specified keys. getkeycodes Displays the kernel scancode-to-keycode mapping table. getopts A utility to parse positional parameters. gpasswd Allows an administrator to change group passwords. gpg Enables encryption and signing services as per the OpenPGP standard. gpgsplit Used to split an OpenPGP message into packets. gpgv Used to verify OpenPGP signatures. gpm It enables cut and paste functionality and a mouse server for the Linux console. gprof Shows call graph profile data. grep Searches input files for a given pattern and displays the relevant lines. groff Serves as the front-end of the groff document formatting system. groffer Displays groff files and man pages. groupadd Used to add a new user group. groupdel Used to remove a user group. groupmod Used to modify a group definition. groups Showthe group(s) to which a user belongs. grpck Verifies the integrity of group files. grpconv Creates agshadow file from a group or an already existing gshadow. gs Invokes Ghostscript, and interpreter and previewer for Adobe’s PostScript and PDF languages. gunzip A utility to compress/expand files. gzexe Used compress executable files in place and have them automatically uncompress and run at a later stage. gzip A utility to compress/expand files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) H Command Description halt Command used to half the machine. hash Shows the path for the commands executed in the shell. hdparm Show/configure parameters for SATA/IDE devices. head Shows first 10 lines from each specified file. help Display’s help for a built-in command. hexdump Shows specified file output in hexadecimal, octal, decimal, or ASCII format. history Shows the command history. host A utility to perform DNS lookups. hostid Shows host’s numeric ID in hexadecimal format. hostname Display/set the hostname of the system. hostnamectl Provides a proper API used to control Linux system hostname and change its related settings. htdigest Manage the user authentication file used by the Apache web server. htop An interactive process viewer for the command line. hwclock Show or configure the system’s hardware clock. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) I Command Description iconv Convert text file from one encoding to another. id Show user and group information for a specified user. if Execute a command conditionally. ifconfig Used to configure network interfaces. ifdown Stops a network interface. iftop It is a network analyzing tool used by system administrators to view the bandwidth related stats. ifup Starts a network interface. imapd An IMAP (Interactive Mail Access Protocol) server daemon. import Capture an X server screen and saves it as an image. inetd Extended internet services daemon, it starts the programs that provide internet services. info Used to read the documentation in Info format. init Systemd system and service manager. insmod A program that inserts a module into the Linux kernel. install Used to copy files to specified locations and set attributions during the install process. iostat Shows statistics for CPU, I/O devices, partitions, network filesystems. iotop Used to display and monitor the disk IO usage details and even gets a table of existing IO utilization by the process. ip Display/manipulate routing, devices, policy, routing and tunnels. ipcrm Used to remove System V interprocess communication (IPC) objects and associated data structures. ipcs Show information on IPC facilities for which calling process has read access. iptables Administration tool for IPv4 packet filtering and NAT. iptables-restore Used to restore IP tables from data specified in the input or a file. iptables-save Used to dump IP table contents to standard output. iwconfig Used to display the parameters, and the wireless statistics which are extracted from /proc/net/wireless. isodump A utility that shows the content iso9660 images to verify the integrity of directory contents. isoinfo A utility to perform directory like listings of iso9660 images. isosize Show the length of an iso9660 filesystem contained in a specified file. isovfy Verifies the integrity of an iso9660 image. ispell A CLI-based spell-check utility. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) J Command Description jobs Show the list of active jobs and their status. join For each pair of input lines, join them using a command field and display on standard output. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) K Command Description kbd_mode Set a keyboard mode. Without arguments, shows the current keyboard mode. kbdrate Reset keyboard repeat rate and delay time. kill Send a kill (termination) signal to one more processes. killall Kills a process(es) running a specified command. killall5 A SystemV killall command. Kills all the processes excluding the ones which it depends on. klogd Control and prioritize the kernel messages to be displayed on the console, and log them through syslogd. kudzu Used to detect new and enhanced hardware by comparing it with existing database. Only for RHEL and derivatives. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) L Command Description last Shows a list of recent logins on the system by fetching data from /var/log/wtmp file. lastb Shows the list of bad login attempts by fetching data from /var/log/btmp file. lastlog Displays information about the most recent login of all users or a specified user. ld The Unix linker, it combines archives and object files. It then puts them into one output file, resolving external references. ldconfig Configure dynamic linker run-time bindings. ldd Shows shared object dependencies. less Displays contents of a fileone page at a time. It’s advanced than more command. lesskey Used to specify key bindings for less command. let Used to perform integer artithmetic on shell variables. lftp An FTP utility with extra features. lftpget Uses lftop to retrieve HTTP, FTP, and other protocol URLs supported by lftp. link Create links between two files. Similar to ln command. ln Create links between files. Links can be hard (two names for the same file) or soft (a shortcut of the first file). loadkeys Load keyboard translation tables. local Used to create function variables. locale Shows information about current or all locales. locate Used to find files by their name. lockfile Create semaphore file(s) which can be used to limit access to a file. logger Make entries in the system log. login Create a new session on the system. logname Shows the login name of the current user. logout Performs the logout operation by making changes to the utmp and wtmp files. logrotate Used for automatic rotation, compression, removal, and mailing of system log files. look Shows any lines in a file containing a given string in the beginning. losetup Set up and control loop devices. lpadmin Used to configure printer and class queues provided by CUPS (Common UNIX Printing System). lpc Line printer control program, it provides limited control over CUPS printer and class queues. lpinfo Shows the list of available devices and drivers known to the CUPS server. lpmove Move on or more printing jobs to a new destination. lpq Shows current print queue status for a specified printer. lpr Used to submit files for printing. lprint Used to print a file. lprintd Used to abort a print job. lprintq List the print queue. lprm Cancel print jobs. lpstat Displays status information about current classes, jobs, and printers. ls Shows the list of files in the current directory. lsattr Shows file attributes on a Linux ext2 file system. lsblk Lists information about all available or the specified block devices. lshw Used to generate the detailed information of the system’s hardware configuration from various files in the /proc directory. lsmod Show the status of modules in the Linux kernel. lsof List open files. lspci List all PCI devices. lsusb List USB devices. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) M Command Description m4 Macro processor. mail Utility to compose, receive, send, forward, and reply to emails. mailq Shows to list all emails queued for delivery (sendmail queue). mailstats Shows current mail statistics. mailto Used to send mail with multimedia content in MIME format. make Utility to maintain groups of programs, recompile them if needed. makedbm Creates an NIS (Network Information Services) database map. makemap Creates database maps used by the keyed map lookups in sendmail. man Shows manual pages for Linux commands. manpath Determine search path for manual pages. mattrib Used to change MS-DOS file attribute flags. mbadblocks Checks MD-DOS filesystems for bad blocks. mcat Dump raw disk image. mcd Used to change MS-DOS directory. mcopy Used to copy MS-DOS files from or to Unix. md5sum Used to check MD5 checksum for a file. mdel, mdeltree Used to delete MS-DOS file. mdeltree recursively deletes MS-DOS directory and its contents. mdir Used to display an MS-DOS directory. mdu Used to display the amount of space occupied by an MS-DOS directory. merge Three-way file merge. Includes all changes from file2 and file3 to file1. mesg Allow/disallow osends to sedn write messages to your terminal. metamail For sending and showing rich text or multimedia email using MIME typing metadata. metasend An interface for sending non-text mail. mformat Used to add an MS-DOS filesystem to a low-level formatted floppy disk. mimencode Translate to/from MIME multimedia mail encoding formats. minfo Display parameters of an MS-DOS filesystem. mkdir Used to create directories. mkdosfs Used to create an MS-DOS filesystem under Linux. mke2fs Used create an ext2/ext3/ext4 filesystem. mkfifo Used to create named pipes (FIFOs) with the given names. mkfs Used to build a Linux filesystem on a hard disk partition. mkfs.ext3 Same as mke2fs, create an ext3 Linux filesystem. mkisofs Used to create an ISO9660/JOLIET/HFS hybrid filesystem. mklost+found Create a lost+found directory on a mounted ext2 filesystem. mkmanifest Makes alist of file names and their DOS 8.3 equivalent. mknod Create a FIFO, block (buffered) special file, character (unbuffered) special file with the specified name. mkraid Used to setup RAID device arrays. mkswap Set up a Linux swap area. mktemp Create a temporary file or directory. mlabel Make an MD-DOS volume label. mmd Make an MS-DOS subdirectory. mmount Mount an MS-DOS disk. mmove Move or rename an MS-DOS file or subdirectory. mmv Mass move and rename files. modinfo Show information about a Linux kernel module. modprobe Add or remove modules from the Linux kernel. more Display content of a file page-by-page. most Browse or page through a text file. mount Mount a filesystem. mountd NFS mount daemon. mpartition Used to report processor related statistics. mpstat Partition an MS-DOS disk. mpg123 Command-line mp3 player. mpg321 Similar to mpg123. mrd Remove an MS-DOS subdirectory. mren Rename an existing MS-DOS file. mshowfat Show FTA clusters allocated to a file. mt Control magnetic tape drive operation. mtools Utilities to access MS-DOS disks. mtoolstest Tests and displays the mtools configuration files. mtr A network diagnostic tool. mtype Display contents of an MS-DOS file. mv Move/rename files or directories. mzip Change protection mode and eject disk on Zip/Jaz drive. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) N Command Description named Internet domain name server. namei Follow a pathname until a terminal point is found. nameif Name network interfaces based on MAC addresses. nc Netcat utility. Arbitrary TCP and UDP connections and listens. netstat Show network information. newaliases Rebuilds mail alias database. newgrp Log-in to a new group. newusers Update/create new users in batch. nfsd Special filesystem for controlling Linux NFS server. nfsstat List NFS statistics. nice Run a program with modified scheduling priority. nl Show numbered line while displaying the contents of a file. nm List symbols from object files. nohup Run a command immune to hangups. notify-send A program to send desktop notifications. nslookup Used performs DNS queries. Read this article for more info. nsupdate Dynamic DNS update utility. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) O Command Description objcopy Copy and translate object files. objdump Display information from object files. od Dump files in octal and other formats. op Operator access, allows system administrators to grant users access to certain root operations that require superuser privileges. open Open a file using its default application. openvt Start a program on a new virtual terminal (VT). [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) P Command Description passwd Change user password. paste Merge lines of files. Write to standard output, TAB-separated lines consisting of sequentially corresponding lines from each file. patch Apply a patchfile (containing differences listing by diff program) to an original file. pathchk Check if file names are valid or portable. perl Perl 5 language interpreter. pgrep List process IDs matching the specified criteria among all the running processes. pidof Find process ID of a running program. ping Send ICMP ECHO_REQUEST to network hosts. pinky Lightweight finger. pkill Send kill signal to processes based on name and other attributes. pmap Report memory map of a process. popd Removes directory on the head of the directory stack and takes you to the new directory on the head. portmap Converts RPC program numbers to IP port numbers. poweroff Shuts down the machine. pppd Point-to-point protocol daemon. pr Convert (column or paginate) text files for printing. praliases Prints the current system mail aliases. printcap Printer capability database. printenv Show values of all or specified environment variables. printf Show arguments formatted according to a specified format. ps Report a snapshot of the current processes. ptx Produce a permuted index of file contents. pushd Appends a given directory name to the head of the stack and then cd to the given directory. pv Monitor progress of data through a pipe. pwck Verify integrity of password files. pwconv Creates shadow from passwd and an optionally existing shadow. pwd Show current directory. python Computer programming language often used to build websites and software, automate tasks, and conduct data analysis. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Q Command Description quota Shows disk usage, and space limits for a user or group. Without arguments, only shows user quotas. quotacheck Used to scan a file system for disk usage. quotactl Make changes to disk quotas. quotaoff Enable enforcement of filesystem quotas. quotaon Disable enforcement of filesystem quotas. quotastats Shows the report of quota system statistics gathered from the kernel. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) R Command Description raidstart Start/stop RAID devices. ram RAM disk device used to access the RAM disk in raw mode. ramsize Show usage information for the RAM disk. ranlib Generate index to the contents of an archive and store it in the archive. rar Create and manage RAR file in Linux. rarpd Respond to Reverse Address Resolution Protocol (RARP) requests. rcp Remote copy command to copy files between remote computers. rdate Set system date and time by fetching information from a remote machine. rdev Set or query RAM disk size, image root device, or video mode. rdist Remote file distribution client, maintains identical file copies over multiple hosts. rdistd Start the rdist server. read Read from a file descriptor. readarray Read lines from a file into an array variable. readcd Read/write compact disks. readelf Shows information about ELF (Executable and Linkable format) files. readlink Display value of a symbolic link or canonical file name. readonly Mark functions and variables as read-only. reboot Restart the machine. reject Accept/reject print jobs sent to a specified destination. remsync Synchronize remote files over email. rename Rename one or more files. renice Change priority of active processes. repquota Report disk usage and quotas for a specified filesystem. reset Reinitialize the terminal. resize2fs Used to resize ext2/ext3/ext4 file systems. restore Restore files from a backup created using dump. return Exit a shell function. rev Show contents of a file, reversing the order of characters in every line. rexec Remote execution client for exec server. rexecd Remote execution server. richtext View “richtext” on an ACSII terminal. rlogin Used to connect a local host system with a remote host. rlogind Acts as the server for rlogin.It facilitates remote login, and authentication based on privileged port numbers from trusted hosts. rm Removes specified files and directories (not by default). rmail Handle remote mail received via uucp. rmdir Used to remove empty directories. rmmod A program to remove modules from Linux kernel. rndc Name server control utility. Send command to a BIND DNS server over a TCP connection. rootflags Show/set flags for the kernel image. route Show/change IP routing table. routed A daemon, invoked at boot time, to manage internet routing tables. rpcgen An RPC protocol compiler. Parse a file written in the RPC language. rpcinfo Shows RPC information. Makes an RPC call to an RPC server and reports the findings. rpm A package manager for Linux distributions. Originally developed for RedHat Linux. rsh Remote shell. Connects to a specified host and executes commands. rshd A daemon that acts as a server for rsh and rcp commands. rsync A versitile to for copying files remotely and locally. runlevel Shows previous and current SysV runlevel. rup Remote status display. Shows current system status for all or specified hosts on the local network. ruptime Shows uptime and login details of the machines on the local network. rusers Shows the list of the users logged-in to the host or on all machines on the local network. rusersd The rsuerd daemon acts as a server that responds to the queries from rsuers command. rwall Sends messages to all users on the local network. rwho Reports who is logged-in to the hosts on the local network. rwhod Acts as a server for rwho and ruptime commands. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) S Command Description sane-find-scanner Find SCSI and USB scanner and determine their device files. sar Used to monitor Linux system’s resources like CPU usage, Memory utilization, I/O devices consumption, etc.. scanadf Retrieve multiple images from a scanner equipped with an automatic document feeder (ADF). scanimage Read images from image acquisition devices (scanner or camera) and display on standard output in PNM (Portable aNyMap) format. scp Copy files between hosts on a network securely using SSH. screen A window manager that enables multiple pseudo-terminals with the help of ANSI/VT100 terminal emulation. script Used to make a typescript of everything displayed on the screen during a terminal session. scriptreplay Used to replay a typescript/terminal_activity stored in the log file that was recorded by the script command. sdiff Shows two files side-by-side and highlights the differences. sed Stream editor for filtering and transforming text (from a file or a pipe input). select Synchronous I/O multiplexing. sendmail It’s a mail router or an MTA (Mail Transfer Agent). sendmail support can send a mail to one or more recipients using necessary protocols. sensors Shows the current readings of all sensor chips. seq Displays an incremental sequence of numbers from first to last. set Used to manipulate shell variables and functions. setfdprm Sets floppy disk parameters as provided by the user. setkeycodes Load kernel scancode-to-keycode mapping table entries. setleds Show/change LED light settings of the keyboard. setmetamode Define keyboard meta key handling. Without arguments, shows current meta key mode. setquota Set disk quotas for users and groups. setsid Run a program in a new session. setterm Set terminal attributes. sftp Secure File Transfer program. sh Command interpreter (shell) utility. sha1sum Compute and check 160-bit SHA1 checksum to verify file integrity. shift Shift positional parameters. shopt Shell options. showkey Examines codes sent by the keyboard displays them in printable form. showmount Shows information about NFS server mount on the host. shred Overwrite a file to hide its content (optionally delete it), making it harder to recover it. shutdown Power-off the machine. size Lists section size and the total size of a specified file. skill Send a signal to processes. slabtop Show kernel slab cache information in real-time. slattach Attack a network interface to a serial line. sleep Suspend execution for a specified amount of time (in seconds). slocate Display matches by searching filename databases. Takes ownership and file permission into consideration. snice Reset priority for processes. sort Sort lines of text files. source Run commands from a specified file. split Split a file into pieces of fixed size. ss Display socket statistics, similar to netstat. ssh An SSH client for logging in to a remote machine. It provides encrypted communication between the hosts. ssh-add Adds private key identities to the authentication agent. ssh-agent It holds private keys used for public key authentication. ssh-keygen It generates, manages, converts authentication keys for ssh. ssh-keyscan Gather ssh public keys. sshd Server for the ssh program. stat Display file or filesystem status. statd A daemon that listens for reboot notifications from other hosts, and manages the list of hosts to be notified when the local system reboots. strace Trace system calls and signals. strfile Create a random access file for storing strings. strings Search a specified file and prints any printable strings with at least four characters and followed by an unprintable character. strip Discard symbols from object files. stty Change and print terminal line settings. su Change user ID or become superuser. sudo Execute a command as superuser. sum Checksum and count the block in a file. suspend Suspend the execution of the current shell. swapoff Disable devices for paging and swapping. swapon Enable devices for paging and swapping. symlink Create a symbolic link to a file. sync Synchronize cached writes to persistent storage. sysctl Configure kernel parameters at runtime. sysklogd Linux system logging utilities. Provides syslogd and klogd functionalities. syslogd Read and log system messages to the system console and log files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) T Command Description tac Concatenate and print files in reverse order. Opposite of cat command. tail Show the last 10 lines of each specified file(s). tailf Follow the growth of a log file. (Deprecated command) talk A two-way screen-oriented communication utility that allows two user to exchange messages simultaneously. talkd A remote user communication server for talk . tar GNU version of the tar archiving utility. Used to store and extract multiple files from a single archive. taskset Set/retrieve a process’s CPU affinity. tcpd Access control utility for internet services. tcpdump Dump traffic on network. Displays a description of the contents of packets on a network interface that match the boolean expression. tcpslice Extract pieces of tcpdump files or merge them. tee Read from standard input and write to standard output and files. telinit Change SysV runlevel. telnet Telnet protocol user interface. Used to interact with another host using telnet. telnetd A server for the telnet protocol. test Check file type and compare values. tftp User interface to the internet TFTP (Trivial File Transfer Protocol). tftpd TFTP server. time Run programs and summarize system resource usage. timeout Execute a command with a time limit. times Shows accumulated user and system times for the shell and it’s child processes. tload Shows a graph of the current system load average to the specified tty. tmpwatch Recursively remove files and directories which haven’t been accessed for the specified period of time. top Displays real-time view of processes running on the system. touch Change file access and modification times. tput Modify terminal-dependent capabilities, color, etc. tr Translate, squeeze, or delete characters from standard input and display on standard output. tracepath Traces path to a network host discovering MTU (Maximum Transmission Unit) along this path. traceroute Traces the route taken by the packets to reach the network host. trap Trap function responds to hardware signals. It defines and creates handlers to run when the shell receives signals. tree A recursive directory listing program that produces a depth-indented listing of files. troff The troff processor of the groff text formatting system. TRUE Exit with a status code indicating success. tset Initialize terminal. tsort Perform topological sort. tty Display the filename of the terminal connected to standard input. tune2fs Adjust tuneable filesystem parameters on ext2/ext3/ext4 filesystems. tunelp Set various parameters for the line printer devices. type Write a description for a command type. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) U Command Description ul Underline text. ulimit Get and set user limits for the calling process. umask Set file mode creation mask. umount Unmount specified file systems. unalias Remove alias definitions for specified alias names. uname Show system information. uncompress Uncompress the files compressed with the compress command. unexpand Convert spaces to tabs for a specified file. unicode_start Put keyboard and console in Unicode mode. unicode_stop Revert keyboard and console from Unicode mode. uniq Report or omit repeating lines. units Convert units from one scalar to another. unix2dos Converts a Unix text file to DOS format. unrar Extract files from a RAR archive. unset Remove variable or function names. unshar Unpack shell archive scripts. until Execute command until a given condition is true. uptime Tell how long the system has been running. useradd Create a new user or update default user information. userdel Delete a user account and related files. usermod Modify a user account. username It provides a set of commands to fetch username and its configurations from the Linux host. users Show the list of active users on the machine. usleep Suspend execution for microsecond intervals. uudecode Decode a binary file. uuencode Encode a binary file. uuidgen Created a new UUID (Universally Unique Identifier) table. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) V Command Description vdir Same as ls -l -b . Verbosely list directory contents. vi A text editor utility. vidmode Set the video mode for a kernel image. Displays current mode value without arguments. Alternative: rdev -v vim Vi Improved, a text-based editor which is a successor to vi. vmstat Shows information about processes, memory, paging, block IO, traps, disks, and CPU activity. vnstat Used by system administrators in order to monitor network parameters such as bandwidth consumption or maybe some traffic flowing in or out. volname Returns volume name for a device formatted with an ISO-9660 filesystem. For example, CD-ROM. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) W Command Description w Show who is logged-on and what they’re doing. wait Waits for a specified process ID(s) to terminate and returns the termination status. wall Display a message on the terminals all the users who are currently logged-in. warnquota Send mail to the users who’ve exceeded their disk quota soft limit. watch Runs commands repeatedly until interrupted and shows their output and errors. wc Print newline, word, and byte count for each of the specified files. wget A non-interactive file download utility. whatis Display one line manual page descriptions. whereis Locate the binary, source, and man page files for a command. which For a given command, lists the pathnames for the files which would be executed when the command runs. while Conditionally execute commands (while loop). who Shows who is logged on. whoami Displays the username tied to the current effective user ID. whois Looks for an object in a WHOIS database write Display a message on other user’s terminal. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) X Command Description xargs Runs a command using initial arguments and then reads remaining arguments from standard input. xdg-open Used to open a file or URL in an application preferred by the user. xinetd Extended internet services daemon. Works similar to inetd. xz Compress/ Decompress .xz and .lzma files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Y Command Description yacc Yet Another Compiler Compiler, a GNU Project parser generator. yes Repeatedly output a line with a specified string(s) until killed. ypbind A daemon that helps client processes to connect to an NIS server. ypcat Shows the NIS map (or database) for the specified MapName parameter. ypinit Sets up NIS maps on an NIS server. ypmatch Shows values for specified keys from an NIS map. yppasswd Change NIS login password. yppasswdd Acts as a server for the yppasswd command. Receives and executes requests. yppoll Shows the ID number or version of NIS map currently used on the NIS server. yppush Forces slave NIS servers to copy updated NIS maps. ypserv A daemon activated at system startup. It looks for information in local NIS maps. ypset Point a client (running ypbind) to a specific server (running ypserv). yptest Calls various functions to check the configuration of NIS services. ypwhich Shows the hostname for NIS server or master server for a given map. ypxfr Transfers NIS server map from server to a local host. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Z Command Description zcat Used to compress/uncompress files. Similar to gzip zcmp Compare compressed files. zdiff Compare compressed files line by line. zdump Displays time for the timezone mentioned. zforce Adds .gz extension to all gzipped files. zgrep Performs grep on compressed files. zic Creates time conversion information files using the specified input files. zip A file compression and packaging utility. zless Displays information of a compressed file (using less command) on the terminal one screen at a time. zmore Displays output of a compressed file (using more command) on the terminal one page at a time. znew Recompress .z files to .gz. files. Credits: fossbytes & geeksforgeeks [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Quick cheat sheet 📝 >**Note** > Examples like `-a|--all` option flags means, single `-` used for _short_ option(-a) **or**| double `--` used for _long_ option(--all). Both was added for educational purpose.### Contents- [Command Information](#command-information)- [Command History](#command-history)- [Navigating Directories](#navigating-directories)- [Creating Directories](#creating-directories)- [Moving Directories](#moving-directories)- [Deleting Directories](#deleting-directories)- [Creating Files](#creating-files)- [Standard Output, Error and Input](#standard-output-standard-error-and-standard-input)- [Moving Files](#moving-files)- [Deleting Files](#deleting-files)- [Reading Files](#reading-files)- [File Permissions](#file-permissions)- [Finding Files](#finding-files)- [Find in Files](#find-in-files)- [Replace in Files](#replace-in-files)- [Symbolic Links](#symbolic-links)- [Compressing Files](#compressing-files)- [Decompressing Files](#decompressing-files)- [Packages](#packages)- [Disk Usage](#disk-usage)- [Memory Usage](#memory-usage)- [Shutdown and Reboot](#shutdown-and-reboot)- [Identifying Processes](#identifying-processes)- [Process Priority](#process-priority)- [Killing Processes](#killing-processes)- [Date & Time](#date--time)- [Scheduled Tasks](#scheduled-tasks)- [User Mangement](#user-management)- [HTTP Requests](#http-requests)- [Network Troubleshooting](#network-troubleshooting)- [DNS](#dns)- [Hardware](#hardware)- [System Information](#system-information)- [Terminal Multiplexers](#terminal-multiplexers)- [Secure Shell Protocol (SSH)](#secure-shell-protocol-ssh)- [Secure Copy](#secure-copy)- [Bash Profile](#bash-profile)- [Bash Script](#bash-script)### Command Information```bashman chmod # Display page manual of a commandman -f|--whatis chmod # Display short description about a commandman -k|--apropos permission # Display all related commands from a specific keywordchmod --help # Display usage options of a command```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Command History```bashhistory # View all previous commandshistory | grep foo # View the commands using a specific wordhistory | grep -E|--extended-regexp -i|--ignore-case 'foo1|foo2|foo3' # View the commands using more than 1 specific word(case sensitive)history | head -n|--lines 3 # View the first 3 executed commandshistory 3 # View the last 3 executed commandshistory -d 99 # Clear a command from a specific line history -c # Clears all history commands!! # Run the last command executedtouch foo.sh # <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<┐chmod +x !$ # !$ is the last argument of the last command i.e. foo.sh <<<<┘```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Navigating Directories```bashpwd # Print current directory pathls # List directoriesls -a|--all # List directories including hiddenls -l # List directories in long formls -l -h|--human-readable # List directories in long form with human readable sizesls -t # List directories by modification time, newest firststat foo.txt # List size, created and modified timestamps for a filestat foo # List size, created and modified timestamps for a directorytree # List directory and file treetree -a # List directory and file tree including hiddentree -d # List directory treecd foo # Go to foo sub-directorycd # Go to home directorycd ~ # Go to home directorycd - # Go to last directorypushd foo # Go to foo sub-directory and add previous directory to stackpopd # Go back to directory in stack saved by `pushd````[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Creating Directories ```bashmkdir foo # Create a directorymkdir foo bar # Create multiple directoriesmkdir -p|--parents foo/bar # Create nested directorymkdir -p|--parents {foo,bar}/baz # Create multiple nested directoriesmktemp -d|--directory # Create a temporary directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Moving Directories```bashcp -R|--recursive foo bar # Copy directorymv foo bar # Move directoryrsync -z|--compress -v|--verbose /foo /bar # Copy directory, overwrites destinationrsync --ignore-existing -a|--archive-a|--archive -z|--compress -v|--verbose /foo /bar # Copy directory, without overwriting destinationrsync -avz /foo username@hostname:/bar # Copy local directory to remote directoryrsync -avz username@hostname:/foo /bar # Copy remote directory to local directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Deleting Directories```bashrmdir foo # Delete non-empty directoryrm -r|--recursive foo # Delete directory including contentsrm -r|--recursive -f|--force foo # Delete directory including contents, ignore nonexistent files and never prompt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Creating Files```bashtouch foo.txt # Create file or update existing files modified timestamptouch foo.txt bar.txt # Create multiple filestouch {foo,bar}.txt # Create multiple filestouch test{1..3} # Create test1, test2 and test3 filestouch test{a..c} # Create testa, testb and testc filesmktemp # Create a temporary file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Standard Output, Standard Error and Standard Input```bashecho "foo" > bar.txt # Overwrite file with contentecho "foo" >> bar.txt # Append to file with contentls exists 1> stdout.txt # Redirect the standard output to a filels noexist 2> stderror.txt # Redirect the standard error output to a filels > out.txt 2>&1 # Redirect standard output and error to a filels > /dev/null # Discard standard output and errorread foo # Read from standard input and write to the variable foo```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Moving Files```bashcp foo.txt bar.txt # Copy filemv foo.txt bar.txt # Move filersync -z|--compress -v|--verbose /foo.txt /bar # Copy file quickly if not changedrsync -z|--compress -v|--verbose /foo.txt /bar.txt # Copy and rename file quickly if not changed```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Deleting Files```bashrm foo.txt # Delete filerm -f|--force foo.txt # Delete file, ignore nonexistent files and never prompt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Reading Files```bashcat foo.txt # Print all contentsless foo.txt # Print some contents at a time (g - go to top of file, SHIFT+g, go to bottom of file, /foo to search for 'foo')head foo.txt # Print top 10 lines of filetail foo.txt # Print bottom 10 lines of filetail -f foo.txt # Print bottom 10 lines of file updating with new dataopen foo.txt # Open file in the default editorwc foo.txt # List number of lines words and characters in the file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## File Permissions| # | Permission | rwx | Binary || - | - | - | - || 7 | read, write and execute | rwx | 111 || 6 | read and write | rw- | 110 || 5 | read and execute | r-x | 101 || 4 | read only | r-- | 100 || 3 | write and execute | -wx | 011 || 2 | write only | -w- | 010 || 1 | execute only | --x | 001 || 0 | none | --- | 000 |For a directory, execute means you can enter a directory.| User | Group | Others | Description || - | - | - | - || 6 | 4 | 4 | User can read and write, everyone else can read (Default file permissions) || 7 | 5 | 5 | User can read, write and execute, everyone else can read and execute (Default directory permissions) |- u - User- g - Group- o - Others- a - All of the above```bashls -l /foo.sh # List file permissionschmod +100 foo.sh # Add 1 to the user permissionchmod -100 foo.sh # Subtract 1 from the user permissionchmod u+x foo.sh # Give the user execute permissionchmod g+x foo.sh # Give the group execute permissionchmod u-x,g-x foo.sh # Take away the user and group execute permissionchmod u+x,g+x,o+x foo.sh # Give everybody execute permissionchmod a+x foo.sh # Give everybody execute permissionchmod +x foo.sh # Give everybody execute permission```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Finding FilesFind binary files for a command.```bashtype -a wget # Display all locations of executablewhich -a wget # Display all locations of executables whereis wget # Find the binary, source, and manual page files````locate` uses an index and is fast.```bashupdatedb # Update the indexlocate foo.txt # Find a filelocate --ignore-case # Find a file and ignore caselocate f*.txt # Find a text file starting with 'f'````find` doesn't use an index and is slow.```bashfind /path -name foo.txt # Find a filefind /path -iname foo.txt # Find a file with case insensitive searchfind /path -name "*.txt" # Find all text filesfind /path -name foo.txt -delete # Find a file and delete itfind /path -name "*.png" -exec pngquant {} # Find all .png files and execute pngquant on itfind /path -type f -name foo.txt # Find a filefind /path -type d -name foo # Find a directoryfind /path -type l -name foo.txt # Find a symbolic linkfind /path -type f -mtime +30 # Find files that haven't been modified in 30 daysfind /path -type f -mtime +30 -delete # Delete files that haven't been modified in 30 days```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Find in Files```bashgrep 'foo' /bar.txt # Search for 'foo' in file 'bar.txt'grep 'foo' /bar -r|--recursive # Search for 'foo' in directory 'bar'grep 'foo' /bar -R|--dereference-recursive # Search for 'foo' in directory 'bar' and follow symbolic linksgrep 'foo' /bar -l|--files-with-matches # Show only files that matchgrep 'foo' /bar -L|--files-without-match # Show only files that don't matchgrep 'Foo' /bar -i|--ignore-case # Case insensitive searchgrep 'foo' /bar -x|--line-regexp # Match the entire linegrep 'foo' /bar -C|--context 1 # Add N line of context above and below each search resultgrep 'foo' /bar -v|--invert-match # Show only lines that don't matchgrep 'foo' /bar -c|--count # Count the number lines that matchgrep 'foo' /bar -n|--line-number # Add line numbersgrep 'foo' /bar --colour # Add colour to outputgrep 'foo\|bar' /baz -R # Search for 'foo' or 'bar' in directory 'baz'grep --extended-regexp|-E 'foo|bar' /baz -R # Use regular expressionsgrep -E 'foo|bar' /baz -R # Use regular expressions```### Replace in Files```bashsed 's/fox/bear/g' foo.txt # Replace fox with bear in foo.txt and output to consolesed 's/fox/bear/gi' foo.txt # Replace fox (case insensitive) with bear in foo.txt and output to consolesed 's/red fox/blue bear/g' foo.txt # Replace red with blue and fox with bear in foo.txt and output to consolesed 's/fox/bear/g' foo.txt > bar.txt # Replace fox with bear in foo.txt and save in bar.txtsed 's/fox/bear/g' foo.txt -i|--in-place # Replace fox with bear and overwrite foo.txt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Symbolic Links```bashln -s|--symbolic foo bar # Create a link 'bar' to the 'foo' folderln -s|--symbolic -f|--force foo bar # Overwrite an existing symbolic link 'bar'ls -l # Show where symbolic links are pointing```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Compressing Files### zipCompresses one or more files into *.zip files.```bashzip foo.zip /bar.txt # Compress bar.txt into foo.zipzip foo.zip /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.zipzip foo.zip /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.zipzip -r|--recurse-paths foo.zip /bar # Compress directory bar into foo.zip```### gzipCompresses a single file into *.gz files.```bashgzip /bar.txt foo.gz # Compress bar.txt into foo.gz and then delete bar.txtgzip -k|--keep /bar.txt foo.gz # Compress bar.txt into foo.gz```### tar -cCompresses (optionally) and combines one or more files into a single *.tar, *.tar.gz, *.tpz or *.tgz file.```bashtar -c|--create -z|--gzip -f|--file=foo.tgz /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.tgztar -c|--create -z|--gzip -f|--file=foo.tgz /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.tgztar -c|--create -z|--gzip -f|--file=foo.tgz /bar # Compress directory bar into foo.tgz```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Decompressing Files### unzip```bashunzip foo.zip # Unzip foo.zip into current directory```### gunzip```bashgunzip foo.gz # Unzip foo.gz into current directory and delete foo.gzgunzip -k|--keep foo.gz # Unzip foo.gz into current directory```### tar -x```bashtar -x|--extract -z|--gzip -f|--file=foo.tar.gz # Un-compress foo.tar.gz into current directorytar -x|--extract -f|--file=foo.tar # Un-combine foo.tar into current directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Packages```bashapt update # Refreshes repository indexapt search wget # Search for a packageapt show wget # List information about the wget packageapt list --all-versions wget # List all versions of the packageapt install wget # Install the latest version of the wget packageapt install wget=1.2.3 # Install a specific version of the wget packageapt remove wget # Removes the wget packageapt upgrade # Upgrades all upgradable packagesapt clean # Clears out the local repository of downloaded package filesdpkg -i|--install package_name.deb # Install deb filerpm -i|--install package_name.rpm # Install rpm file ```### Install package source code```bashtar zxvf sourcecode.tar.gzcd sourcecode./configuremakemake install```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Disk Usage```bashdf # List disks, size, used and available spacedf -h|--human-readable # List disks, size, used and available space in a human readable formatdu # List current directory, subdirectories and file sizesdu /foo/bar # List specified directory, subdirectories and file sizesdu -h|--human-readable # List current directory, subdirectories and file sizes in a human readable formatdu -d|--max-depth # List current directory, subdirectories and file sizes within the max depthdu -d 0 # List current directory size```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Memory Usage```bashfree # Show memory usagefree -h|--human # Show human readable memory usagefree -h|--human --si # Show human readable memory usage in power of 1000 instead of 1024free -s|--seconds 5 # Show memory usage and update continuously every five seconds```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Shutdown and Reboot```bashshutdown # Shutdown in 1 minuteshutdown now # Immediately shut downshutdown +5 # Shutdown in 5 minutesshutdown -r|--reboot # Reboot in 1 minuteshutdown -r|--reboot now # Immediately rebootshutdown -r|--reboot +5 # Reboot in 5 minutesshutdown -c # Cancel a shutdown or rebootreboot # Reboot nowreboot -f # Force a reboot```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Identifying Processes```bashtop # List all processes interactivelyhtop # List all processes interactivelyps ax # List all processespidof foo # Return the PID of all foo processesCTRL+Z # Suspend a process running in the foregroundbg # Resume a suspended process and run in the backgroundfg # Bring the last background process to the foregroundfg 1 # Bring the background process with the PID to the foregroundsleep 30 & # Sleep for 30 seconds and move the process into the backgroundjobs # List all background jobsjobs -p # List all background jobs with their PIDlsof # List all open files and the process using themlsof -itcp:4000 # Return the process listening on port 4000```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Process PriorityProcess priorities go from -20 (highest) to 19 (lowest).```bashnice -n -20 foo # Change process priority by namerenice 20 PID # Change process priority by PIDps -o ni PID # Return the process priority of PID```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Killing Processes```bashCTRL+C # Kill a process running in the foregroundkill PID # Shut down process by PID gracefully. Sends TERM signal.kill -9 PID # Force shut down of process by PID. Sends SIGKILL signal.pkill foo # Shut down process by name gracefully. Sends TERM signal.pkill -9 foo # force shut down process by name. Sends SIGKILL signal.killall foo # Kill all process with the specified name gracefully.```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Date & Time```bashdate # Print the date and timedate --iso-8601 # Print the ISO8601 datedate --iso-8601=ns # Print the ISO8601 date and timedate -s "02 DEC 2020 12:02:02" # Manually change date and timedpkg-reconfigure tzdata # Change date/timezoneuptime # Print how long the system has been runningtime tree # Print amount of time to tree takes to execute```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Scheduled Tasks```pre * * * * *Minute, Hour, Day of month, Month, Day of the week``````bashcrontab -l # List cron tabcrontab -e # Edit cron tab in Vimcrontab /path/crontab # Load cron tab from a filecrontab -l > /path/crontab # Save cron tab to a file* * * * * foo # Run foo every minute*/15 * * * * foo # Run foo every 15 minutes0 * * * * foo # Run foo every hour15 6 * * * foo # Run foo daily at 6:15 AM44 4 * * 5 foo # Run foo every Friday at 4:44 AM0 0 1 * * foo # Run foo at midnight on the first of the month0 0 1 1 * foo # Run foo at midnight on the first of the yearat -l # List scheduled tasksat -c 1 # Show task with ID 1at -r 1 # Remove task with ID 1at now + 2 minutes # Create a task in Vim to execute in 2 minutesat 12:34 PM next month # Create a task in Vim to execute at 12:34 PM next monthat tomorrow # Create a task in Vim to execute tomorrow```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## User Management```bashsudo su # switch to root usersudo foo # execute command as the root usersu username # switch to a different useradduser username # To add a new userpasswd -l|--lock username # To change the password of a useruserdel username # To remove useruserdel -r|--remove username # To remove user with home directory and mail spoolusermod -a|--append -G|--groups GROUPNAME USERNAME # To add a user to a groupdeluser USER GROUPNAME # To remove a user from a grouplast # Shows information of all the users logged inlast username # Gives information of a particular user```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## HTTP Requests```bashcurl https://example.com # Return response bodycurl -i|--include https://example.com # Include status code and HTTP headerscurl -L|--location https://example.com # Follow redirectscurl -O|--remote-name foo.txt https://example.com # Output to a text filecurl -H|--header "User-Agent: Foo" https://example.com # Add a HTTP headercurl -X|--request POST -H "Content-Type: application/json" -d|--data '{"foo":"bar"}' https://example.com # POST JSONcurl -X POST -H --data-urlencode foo="bar" http://example.com # POST URL Form Encodedwget https://example.com/file.txt # Download a file to the current directorywget -O|--output-document foo.txt https://example.com/file.txt # Output to a file with the specified name```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Network Troubleshooting```bashping example.com # Send multiple ping requests using the ICMP protocolping -c 10 -i 5 example.com # Make 10 attempts, 5 seconds apartip addr # List IP addresses on the systemip route show # Show IP addresses to routercurl ifconfig.me # Obtain external IP addressnetstat -i|--interfaces # List all network interfaces and in/out usagenetstat -l|--listening # List all open portstraceroute example.com # List all servers the network traffic goes throughmtr -w|--report-wide example.com # Continually list all servers the network traffic goes throughmtr -r|--report -w|--report-wide -c|--report-cycles 100 example.com # Output a report that lists network traffic 100 timesnmap 0.0.0.0 # Scan for the 1000 most common open ports on localhostnmap 0.0.0.0 -p1-65535 # Scan for open ports on localhost between 1 and 65535nmap 192.168.4.3 # Scan for the 1000 most common open ports on a remote IP addressnmap -sP 192.168.1.1/24 # Discover all machines on the network by ping'ing them```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## DNS```bashdig example.com # Show query information of domain A recordsdig -4 example.com # Show IPv4 A recordsdig -6 example.com # Show IPv6 AAA recordsdig example.com @nameserver # Show query of a specific nameserverdig example.com -p 123 # Show query of a specific port numbercat /etc/resolv.conf # Nameservers filecat /etc/systemd/resolved.conf # DNS resolver config file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Hardware```bashlsusb # List USB deviceslspci # List PCI hardwarelshw # List all hardware```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## System Information```bashuname -s # Print kernel nameuname -r # Print kernel releaseuname -m # Print Architectureuname -o # Print Operating System```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Terminal MultiplexersStart multiple terminal sessions. Active sessions persist reboots. `tmux` is more modern than `screen`.```bashtmux # Start a new session (CTRL-b + d to detach)tmux ls # List all sessionstmux attach -t 0 # Reattach to a sessionscreen # Start a new session (CTRL-a + d to detach)screen -ls # List all sessionsscreen -R 31166 # Reattach to a sessionexit # Exit a session```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Secure Shell Protocol (SSH)```bashssh hostname # Connect to hostname using your current user name over the default SSH port 22ssh -i foo.pem hostname # Connect to hostname using the identity filessh user@hostname # Connect to hostname using the user over the default SSH port 22ssh user@hostname -p 8765 # Connect to hostname using the user over a custom portssh ssh://user@hostname:8765 # Connect to hostname using the user over a custom port```Set default user and port in `~/.ssh/config`, so you can just enter the name next time:```bash$ cat ~/.ssh/configHost name User foo Hostname 127.0.0.1 Port 8765$ ssh name```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Secure Copy```bashscp foo.txt ubuntu@hostname:/home/ubuntu # Copy foo.txt into the specified remote directoryscp ubuntu@hostname:/home/ubuntu/foo.txt /C:\Users\Admin # Copy foo.txt from the specified remote directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Bash Profile- bash - `.bashrc`- zsh - `.zshrc````bash# Always run ls after cdfunction cd { builtin cd "$@" && ls}# Prompt user before overwriting any filesalias cp='cp --interactive'alias mv='mv --interactive'alias rm='rm --interactive'# Always show disk usage in a human readable formatalias df='df -h'alias du='du -h'```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Bash Script### Variables```bash#!/bin/bashfoo=123 # Initialize variable foo with 123declare -i foo=123 # Initialize an integer foo with 123declare -r foo=123 # Initialize readonly variable foo with 123echo $foo # Print variable fooecho ${foo}_'bar' # Print variable foo followed by _barecho ${foo:-'default'} # Print variable foo if it exists otherwise print defaultexport foo # Make foo available to child processesunset foo # Make foo unavailable to child processes and current session```### Environment Variables```bash#!/bin/bashset # List all environment variablesecho $PATH # Print PATH environment variableexport FOO=Bar # Set an environment variable```### Functions```bash#!/bin/bashgreet() { local world="World" echo "$1 $world" return "$1 $world"}greet "Hello"greeting=$(greet "Hello")```### Exit Codes```bash#!/bin/bashexit 0 # Exit the script successfullyexit 1 # Exit the script unsuccessfullyecho $? # Print the last exit code```### Conditional Statements#### Boolean Operators- `$foo` - Is true- `!$foo` - Is false#### Numeric Operators- `-eq` - Equals- `-ne` - Not equals- `-gt` - Greater than- `-ge` - Greater than or equal to- `-lt` - Less than- `-le` - Less than or equal to- `-e` foo.txt - Check file exists- `-z` foo - Check if variable exists#### String Operators- `=` - Equals- `==` - Equals- `-z` - Is null- `-n` - Is not null- `<` - Is less than in ASCII alphabetical order- `>` - Is greater than in ASCII alphabetical order#### If Statements```bash#!/bin/bash[[if [[$foo = 'bar']]; then echo 'one'elif [[$foo = 'bar']] || [[$foo = 'baz']]; then echo 'two'elif [[$foo = 'ban']] && [[$USER = 'bat']]; then echo 'three'else echo 'four'fi]]```#### Inline If Statements```bash#!/bin/bash[[ $USER = 'rehan' ]] && echo 'yes' || echo 'no'```#### While Loops```bash#!/bin/bash[declare -i countercounter=10while [$counter -gt 2]; do echo The counter is $counter counter=counter-1done]```#### For Loops```bash#!/bin/bashfor i in {0..10..2} do echo "Index: $i" donefor filename in file1 file2 file3 do echo "Content: " >> $filename donefor filename in *; do echo "Content: " >> $filename done```#### Case Statements```bash#!/bin/bashecho "What's the weather like tomorrow?"read weathercase $weather in sunny | warm ) echo "Nice weather: " $weather ;; cloudy | cool ) echo "Not bad weather: " $weather ;; rainy | cold ) echo "Terrible weather: " $weather ;; * ) echo "Don't understand" ;;esac``` Inspired by RehanSaeed/Bash-Cheat-Sheet [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents) Special characters 🔣 Char. Description ~ Home directory [tilde]. The path to a user's home directory location. - Previous directory [dash]. Go back to previous directory. / Filename path separator [forward slash]. Separates the components of a filename. It also represents the path to root directory. \ Escape [backslash]. A quoting mechanism for single characters. It preserves the literal value of the next character that follows, with the exception of newline. │ Pipe. It passes the output (stdout) of a previous command to the input (stdin) of the next one, or to the shell. This is a method of chaining commands together. || The OR operator is used to chain commands. It will execute succeeded commands which follows and stops if the preceding command fails. && The AND operator is used to chain commands. It will execute commands only if the first command is successful ; Command separator [semicolon]. Used to separate multiple commands and execute all the ones that is successful. & Run job in background[and]. A command followed by an & will run in the background. # Comment [number sign]. Lines in files beginning with a # (with the exception of #!) are comments and will not be executed. >, >>, < Redirect a command's output or input into a file. >| Force redirection (even if the noclobber option is set). This will forcibly overwrite an existing file. ' ' Single quotes protects the text inside them so that it has a literal meaning. This is a stronger form of quoting than double quotes. " " Whitespace. This is a tab, newline, vertical tab, form feed, carriage return, or space. Bash uses whitespace to determine where words begin and end. ! Reverse (or negate) [exclamation]. The ! operator inverts the exit status of the command to which it is applied. It also inverts the meaning of a test operator. * Wild card [asterisk]. The * character serves as a "wild card" for filename expansion in globbing . By itself, it matches every filename in a given directory. ? Wild card [question mark]. The ? character serves as a single-character "wild card" for filename expansion in globbing, as well as representing one character in an extended regular expression. { } Inline group [curly brackets]. Commands inside the curly braces are treated as if they were one command. It is convenient to use these when Bash syntax requires only one command and a function doesn't feel warranted. ( ) Subshell group [bracket].Commands within are executed in a subshell (a new process) Used much like a sandbox, if a command causes side effects (like changing variables), it will have no effect on the current shell. [ ] Test expression between [ ]. It is part of the shell builtin test. [[ ]] Test expression between [[ ]]. It is more flexible than the single-bracket [ ] test. (( )) Integer expansion. Expand and evaluate integer expression. ;; Terminator in a case option [double semicolon]. ,, , Lowercase conversion in parameter substitution. ^, ^^ Uppercase conversion in parameter substitution. Keyboard controls ⌨️ | Key | Function || :--: | :-- || Ctrl+a | Moves cursor to beginning of text in line || Ctrl+e | Moves cursor to end of text in line || Ctrl+b | Moves cursor backward one character position || Ctrl+f | Moves cursor forward one character position || Ctrl+u | Erase a line of input from cursor right to left of line || Ctrl+k | Erase a line of input from cursor left to right of line || Ctrl+d | Erase character forward from cursor left to right || Ctrl+h | Erase character backward from cursor right to left || Ctrl+w | Erase backwards to first non-alphanumeric character or empty space || Ctrl+p | Fetch previous command from history list || Ctrl+n | Fetch next command from history list || Ctrl+y | Fetch back command previously erased || Ctrl+t | Reverses the position of the character the cursor is on with the previous character || Ctrl+r | Reverse search commands from history list || Ctrl+z | Pauses a foreground job || Ctrl+c | Break/Terminate a foreground job || Ctrl+m | Clear the current line || Ctrl+o | Accept the current line for execution and fetch the next command || Ctrl+l | Clear screen contents (command-line needs to be empty) || Ctrl+s | Suspend || Ctrl+q | Resume || Ctrl+d | Log out from a shell (similar to exit) || | || | || | || Alt+b | Moves cursor one word backwards || Alt+f | Moves cursor one word forward || Alt+d | Erase the next word from cursor left to right || Alt+t | Reverses the position of the word the cursor is in with the previous word || Alt+u | Capitalizes every character from cursor left to right to the end of one word || Alt+l | UnCapitalizes every character from cursor left to right to the end of one word || Alt+r | Reverts any changes to a previously executed command that is edited || Alt+. | Fetch and paste the last word at end of a command from previous commands | Online Cheat Sheet :feelsgood: for quick references of commands and codes cheat.sh Terminal :```bashcurl cht.sh/keyword or curl cheat.sh/keyword``` Browser : https://cht.sh/ keyword or https://cheat.sh/ keyword # #### Offline usage Install cheat script manually Install globally(all users) : bashcurl -s https://cht.sh/:cht.sh | sudo tee /usr/local/bin/cht.sh && sudo chmod +x /usr/local/bin/cht.sh Run :```bashcht.sh keyword ``` To restore the repository download the bundle wget https://archive.org/download/github.com-trinib-Linux-Bash-Commands_-_2022-11-08_23-53-09/trinib-Linux-Bash-Commands_-_2022-11-08_23-53-09.bundle and run: git clone trinib-Linux-Bash-Commands_-_2022-11-08_23-53-09.bundle Source: https://github.com/trinib/Linux-Bash-Commands Uploader: trinib Upload date: 2022-11-08

:godmode: Ultimate list of Linux bash commands # Ultimate list of Linux bash commands_Bash is the [Unix](https://www.google.com/search?q=What+is+UNIX+explain%3F&client=firefox-b-d&sxsrf=ALiCzsZmYtgn9ctD5vHAqgVFkM5tZ514pw%3A1667926333803&ei=PYlqY6XIMNmNwbkPqeK3qAo&ved=0ahUKEwjl2ozlhZ_7AhXZRjABHSnxDaUQ4dUDCA4&uact=5&oq=What+is+UNIX+explain%3F&gs_lcp=Cgxnd3Mtd2l6LXNlcnAQAzIFCAAQgAQyBQgAEIAEMgUIABCABDIGCAAQFhAeMgYIABAWEB4yBggAEBYQHjIFCAAQhgMyBQgAEIYDMgUIABCGAzIFCAAQhgM6CggAEEcQ1gQQsAM6BwgAELADEENKBAhNGAFKBAhBGABKBAhGGABQnAFYnAFgvwNoAXABeACAAa0BiAGtAZIBAzAuMZgBAKABAqABAcgBCsABAQ&sclient=gws-wiz-serp) command-line interface (CLI). Also called the terminal, the command line, or the shell. It's a command language that allows us to work with files on our computers in a way that's far more efficient and powerful than using a GUI (graphical user interface)_ A to Z command list 📚 > **Note** > Use `Ctrl+f` to search in browsers🔎 Table #### │ [A](#-a) │ [B](#-b) │ [C](#-c) │ [D](#-d) │ [E](#-e) │ [F](#-f) │ [G](#-g) │ [H](#-h) │ [I](#-i) │ [J](#-j) │ [K](#-k) │ [L](#-l) │ [M](#-m) │ [N](#-n) │ [O](#-o) │ [P](#-p) │ [Q](#-q) │ [R](#-r) │ [S](#-s) │ [T](#-t) │ [U](#-u) │ [V](#-v) │ [W](#-w) │ [X](#-x) │ [Y](#-y) │ [Z](#-z) │ A Command Description accept Accept or Reject jobs to a destination, such as a printer. access Check a user’s RWX(read, write and execute) permission for a file. accton Used to turn on or turn off the process for accounting or change info process accounting file. aclocal Used to automatically generate aclocal.m4 files from configure.in file. aconnect ALSA(Advanced Linux Sound Architecture) sequencer connection manager. acpi Show information about the Advanced Configuration and Power Interface. acpi_available Check if ACPI(Advanced Configuration and Power Interface) functionality exists on the system. acpid Informs user-space programs about ACPI events. addr2line Used to convert addresses into file names and line numbers. addresses Formats for internet mail addresses. agetty An alternative Linux Getty that manages physical or virtual terminals to allow multi-user access alias Create an alias, a shortcut that references a command. alsactl Access advanced controls for ALSA soundcard driver. amidi Perform read/write operation for ALSA RawMIDI ports. amixer Access CLI-based mixer for ALSA soundcard driver. anacron Used to run commands periodically. aplay Sound recorder and player for CLI. aplaymidi CLI utility used to play MIDI files. apm Show Advanced Power Management (APM) hardware info on older systems. apmd Used to handle events reported by APM BIOS drivers. apropos Shows the list of all man pages containing a specific keyword. apt Advanced Package Tool, a package management system for Debian and derivatives. apt-get Command-line utility to install/remove/update packages based on APT system. aptitude Another utility to add/remove/upgrade packages based on the APT system. ar A utility to create/modify/extract from archives. arch Display print machine hardware name. arecord Just like aplay, it’s a sound recorder and player for ALSA soundcard driver. arecordmidi Record standard MIDI files. arp Used to make changes to the system’s ARP cache. as A portable GNU assembler. aspell An interactive spell checker utility. at Used to schedule command execution at specified date & time, reading commands from an input file. atd Used to execute jobs queued by the at command. atq List a user’s pending jobs for the at command. atrm Delete jobs queued by the at command. audiosend Used to send an audio recording as an email. aumix An audio mixer utility. autoconf Generate configuration scripts from a TEMPLATE-FILE and send the output to standard output. autoheader Create a template header for configure. automake Creates GNU standards-compliant Makefiles from template files. autoreconf Update generated configuration files. autoscan Generate a preliminary configure.in file. autoupdate Update a configure.in file to newer autoconf. awk A scripting language used for manipulating data and generating reports. Also used to find and replace text in a file(s). [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) B Command Description badblocks Search a disk partition for bad sectors. banner Used to print characters as a poster. basename Used to display filenames with directory or suffix. bash GNU Bourne-Again Shell. batch Used to run commands entered on a standard input. bc Access the GNU bc calculator utility. bg Send processes to the background. biff Notify about incoming mail and sender’s name on a system running comsat server. bind Used to attach a name to a socket. bison A GNU parser generator, compatible with yacc. break Used to exit from a loop (eg: for, while, select). builtin Used to run shell builtin commands, make custom functions for commands extending their functionality. bzcmp Used to call the cmp program forbzip2 compressed files. bzdiff Used to call the diff program for bzip2 compressed files. bzgrep Used to call grep for bzip2 compressed files. bzip2 A block-sorting file compressor used to shrink given files. bzless Used to apply ‘less’ (show info one page at a time) to bzip2 compressed files. bzmore Used to apply ‘more’ (an inferior version of less) to bzip2 compressed files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) C Command Description cal Show calendar. cardctl Used to control PCMCIA sockets and select configuration schemes. cardmgr Keeps an eye on the added/removes sockets for PCMCIA devices. case Execute a command conditionally by matching a pattern. cat Used to concatenate files and print them on the screen. cc GNU C and C++ compiler. ccrypt Used for encryption and decryption of data. cd Used to change directory. cdda2wav Used to rip a CD-ROM and make WAV file. cdparanoia Record audio from CD more reliably using data-verification algorithms. cdrdao Used to write all the content specified to a file to a CD all at once. cdrecord Used to record data or audio compact discs. cfdisk Show or change the disk partition table. chage Used to change user password information. chattr Used to change file attributes. chdir Used to change active working directory. chfn Used to change real user name and information. chgrp Used to change group ownership for file. chkconfig Manage execution of runlevel services. chmod Change access permission for a file(s). chown Change the owner or group for a file. chpasswd Update password in a batch. chroot Run a command with root directory. chrt Alter process attributed in real-time. chsh Switch login shell. chvt Change foreground virtual terminal. cksum Perform a CRC checksum for files. clear Used to clear the terminal window. cmp Compare two files (byte by byte). col Filter reverse (and half-reverse) line feeds from the input. colcrt Filter nroff output for CRT previewing. colrm Remove columns from the lines of a file. column A utility that formats its input into columns. comm Used to compare two sorted files line by line. command Used to execute a command with arguments ignoring shell function named command. compress Used to compress one or more file(s) and replacing the originals ones. continue Resume the next iteration of a loop. cp Copy contents of one file to another. cpio Copy files from and to archives. cpp GNU C language processor. cron A daemon to execute scheduled commands. crond Same work as cron. crontab Manage crontab files (containing schedules commands) for users. csplit Split a file into sections on the basis of context lines. ctags Make a list of functions and macro names defined in a programming source file. cupsd A scheduler for CUPS. curl Used to transfer data from or to a server using supported protocols. cut Used to remove sections from each line of a file(s). cvs Concurrent Versions System. Used to track file versions, allow storage/retrieval of previous versions, and enables multiple users to work on the same file. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) D Command Description date Show system date and time. dc Desk calculator utility. dd Used to convert and copy a file, create disk clone, write disk headers, etc. ddrescue Used to recover data from a crashed partition. deallocvt Deallocates kernel memory for unused virtual consoles. debugfs File system debugger for ext2/ext3/ext4 declare Used to declare variables and assign attributes. depmod Generate modules.dep and map files. devdump Interactively displays the contents of device or file system ISO. df Show disk usage. diff Used to compare files line by line. diff3 Compare three files line by line. dig Domain Information Groper, a DNS lookup utility. dir List the contents of a directory. dircolors Set colors for ‘ls’ by altering the LS_COLORS environment variable. dirname Display pathname after removing the last slash and characters thereafter. dirs Show the list of remembered directories. disable Restrict access to a printer. dlpsh Interactive Desktop Link Protocol (DLP) shell for PalmOS. dmesg Examine and control the kernel ring buffer. dmidecode Used when the user wants to retrieve system’s hardware related information such as Processor, RAM(DIMMs), BIOS detail, etc. of Linux system in a readable format. dnsdomainname Show the DNS domain name of the system. dnssec-keygen Generate encrypted Secure DNS keys for a given domain name. dnssec-makekeyset Produce domain key set from one or more DNS security keys generated by dnssec-keygen. dnssec-signkey Sign a secure DNS keyset with key signatures specified in the list of key-identifiers. dnssec-signzone Sign a secure DNS zonefile with the signatures in the specified list of key-identifiers. doexec Used to run an executable with an arbitrary argv list provided. domainname Show or set the name of current NIS (Network Information Services) domain. dosfsck Used to retrieve information or statistics form components of the system such as network connections, IO devices, or CPU, etc. dstat Check and repair MS-DOS file systems. du Show disk usage summary for a file(s). dump Backup utility for ext2/ext3 file systems. dumpe2fs Dump ext2/ext3/ext4 file systems. dumpkeys Show information about the keyboard driver’s current translation tables. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) E Command Description e2fsck Used to check ext2/ext3/ext4 file systems. e2image Store important ext2/ext3/ext4 filesystem metadata to a file. e2label Show or change the label on an ext2/ext3/ext4 filesystem. echo Send input string(s) to standard output i.e. display text on the screen. ed GNU Ed – a line-oriented text editor. edquota Used to edit filesystem quotas using a text editor, such as vi. egrep Search and display text matching a pattern. eject Eject removable media. elvtune Used to set latency in the elevator algorithm used to schedule I/O activities for specified block devices. emacs Emacs text editor command line utility. enable Used to enable/disable shell builtin commands. env Run a command in a modified environment. Show/set/delete environment variables. envsubst Substitute environment variable values in shell format strings. esd Start the Enlightenment Sound Daemon (EsounD or esd). Enables multiple applications to access the same audio device simultaneously. esd-config Manage EsounD configuration. esdcat Use EsounD to send audio data from a specified file. esdctl EsounD control program. esddsp Used to reroute non-esd audio data to esd and control all the audio using esd. esdmon Used to copy the sound being sent to a device. Also, send it to a secondary device. esdplay Use EsounD system to play a file. esdrec Use EsounD to record audio to a specified file. esdsample Sample audio using esd. etags Used to create a list of functions and macros from a programming source file. These etags are used by emacs. For vi, use ctags. ethtool Used to query and control network driver and hardware settings. eval Used to evaluate multiple commands or arguments are once. ex Interactive command exec An interactive line-based text editor. exit Exit from the terminal. expand Convert tabs into spaces in a given file and show the output. expect An extension to the Tcl script, it’s used to automate interaction with other applications based on their expected output. export Used to set an environment variable. expr Evaluate expressions and display them on standard output. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) F Command Description factor Display prime factors of specified integer numbers. false Do nothing, unsuccessfully. Exit with a status code indicating failure. fc Used to list, edit or re-execute the commands previously entered into an interactive shell. fc-cache Make font information cache after scanning the directories. fc-list Show the list of available fonts. fdformat Do a low-level format on a floppy disk. fdisk Make changes to the disk partition table. fetchmail Fetch mail from mail servers and forward it to the local mail delivery system. fg Used to send a job to the foreground. fgconsole Display the number of the current virtual console. fgrep Display lines from a file(s) that match a specified string. A variant of grep. file Determine file type for a file. find Do a file search in a directory hierarchy. finger Display user data including the information listed in .plan and .project in each user’s home directory. fingerd Provides a network interface for the finger program. flex Generate programs that perform pattern-matching on text. fmt Used to convert text to a specified width by filling lines and removing new lines, displaying the output. fold Wrap input line to fit in a specified width. for Expand words and run commands for each one in the resultant list. formail Used to filter standard input into mailbox format. format Used to format disks. free Show free and used system memory. fsck Check and repair a Linux file system ftp File transfer protocol user interface. ftpd FTP server process. function Used to define function macros. Fun Used to draw various type of patterns on the terminal. fuser Find and kill a process accessing a file. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) G Command Description g++ Run the g++ compiler. gawk Used for pattern scanning and language processing. A GNU implementation of AWK language. gcc A C and C++ compiler by GNU. gdb A utility to debug programs and know about where it crashes. getent Shows entries from Name Service Switch Libraries for specified keys. getkeycodes Displays the kernel scancode-to-keycode mapping table. getopts A utility to parse positional parameters. gpasswd Allows an administrator to change group passwords. gpg Enables encryption and signing services as per the OpenPGP standard. gpgsplit Used to split an OpenPGP message into packets. gpgv Used to verify OpenPGP signatures. gpm It enables cut and paste functionality and a mouse server for the Linux console. gprof Shows call graph profile data. grep Searches input files for a given pattern and displays the relevant lines. groff Serves as the front-end of the groff document formatting system. groffer Displays groff files and man pages. groupadd Used to add a new user group. groupdel Used to remove a user group. groupmod Used to modify a group definition. groups Showthe group(s) to which a user belongs. grpck Verifies the integrity of group files. grpconv Creates agshadow file from a group or an already existing gshadow. gs Invokes Ghostscript, and interpreter and previewer for Adobe’s PostScript and PDF languages. gunzip A utility to compress/expand files. gzexe Used compress executable files in place and have them automatically uncompress and run at a later stage. gzip A utility to compress/expand files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) H Command Description halt Command used to half the machine. hash Shows the path for the commands executed in the shell. hdparm Show/configure parameters for SATA/IDE devices. head Shows first 10 lines from each specified file. help Display’s help for a built-in command. hexdump Shows specified file output in hexadecimal, octal, decimal, or ASCII format. history Shows the command history. host A utility to perform DNS lookups. hostid Shows host’s numeric ID in hexadecimal format. hostname Display/set the hostname of the system. hostnamectl Provides a proper API used to control Linux system hostname and change its related settings. htdigest Manage the user authentication file used by the Apache web server. htop An interactive process viewer for the command line. hwclock Show or configure the system’s hardware clock. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) I Command Description iconv Convert text file from one encoding to another. id Show user and group information for a specified user. if Execute a command conditionally. ifconfig Used to configure network interfaces. ifdown Stops a network interface. iftop It is a network analyzing tool used by system administrators to view the bandwidth related stats. ifup Starts a network interface. imapd An IMAP (Interactive Mail Access Protocol) server daemon. import Capture an X server screen and saves it as an image. inetd Extended internet services daemon, it starts the programs that provide internet services. info Used to read the documentation in Info format. init Systemd system and service manager. insmod A program that inserts a module into the Linux kernel. install Used to copy files to specified locations and set attributions during the install process. iostat Shows statistics for CPU, I/O devices, partitions, network filesystems. iotop Used to display and monitor the disk IO usage details and even gets a table of existing IO utilization by the process. ip Display/manipulate routing, devices, policy, routing and tunnels. ipcrm Used to remove System V interprocess communication (IPC) objects and associated data structures. ipcs Show information on IPC facilities for which calling process has read access. iptables Administration tool for IPv4 packet filtering and NAT. iptables-restore Used to restore IP tables from data specified in the input or a file. iptables-save Used to dump IP table contents to standard output. iwconfig Used to display the parameters, and the wireless statistics which are extracted from /proc/net/wireless. isodump A utility that shows the content iso9660 images to verify the integrity of directory contents. isoinfo A utility to perform directory like listings of iso9660 images. isosize Show the length of an iso9660 filesystem contained in a specified file. isovfy Verifies the integrity of an iso9660 image. ispell A CLI-based spell-check utility. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) J Command Description jobs Show the list of active jobs and their status. join For each pair of input lines, join them using a command field and display on standard output. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) K Command Description kbd_mode Set a keyboard mode. Without arguments, shows the current keyboard mode. kbdrate Reset keyboard repeat rate and delay time. kill Send a kill (termination) signal to one more processes. killall Kills a process(es) running a specified command. killall5 A SystemV killall command. Kills all the processes excluding the ones which it depends on. klogd Control and prioritize the kernel messages to be displayed on the console, and log them through syslogd. kudzu Used to detect new and enhanced hardware by comparing it with existing database. Only for RHEL and derivatives. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) L Command Description last Shows a list of recent logins on the system by fetching data from /var/log/wtmp file. lastb Shows the list of bad login attempts by fetching data from /var/log/btmp file. lastlog Displays information about the most recent login of all users or a specified user. ld The Unix linker, it combines archives and object files. It then puts them into one output file, resolving external references. ldconfig Configure dynamic linker run-time bindings. ldd Shows shared object dependencies. less Displays contents of a fileone page at a time. It’s advanced than more command. lesskey Used to specify key bindings for less command. let Used to perform integer artithmetic on shell variables. lftp An FTP utility with extra features. lftpget Uses lftop to retrieve HTTP, FTP, and other protocol URLs supported by lftp. link Create links between two files. Similar to ln command. ln Create links between files. Links can be hard (two names for the same file) or soft (a shortcut of the first file). loadkeys Load keyboard translation tables. local Used to create function variables. locale Shows information about current or all locales. locate Used to find files by their name. lockfile Create semaphore file(s) which can be used to limit access to a file. logger Make entries in the system log. login Create a new session on the system. logname Shows the login name of the current user. logout Performs the logout operation by making changes to the utmp and wtmp files. logrotate Used for automatic rotation, compression, removal, and mailing of system log files. look Shows any lines in a file containing a given string in the beginning. losetup Set up and control loop devices. lpadmin Used to configure printer and class queues provided by CUPS (Common UNIX Printing System). lpc Line printer control program, it provides limited control over CUPS printer and class queues. lpinfo Shows the list of available devices and drivers known to the CUPS server. lpmove Move on or more printing jobs to a new destination. lpq Shows current print queue status for a specified printer. lpr Used to submit files for printing. lprint Used to print a file. lprintd Used to abort a print job. lprintq List the print queue. lprm Cancel print jobs. lpstat Displays status information about current classes, jobs, and printers. ls Shows the list of files in the current directory. lsattr Shows file attributes on a Linux ext2 file system. lsblk Lists information about all available or the specified block devices. lshw Used to generate the detailed information of the system’s hardware configuration from various files in the /proc directory. lsmod Show the status of modules in the Linux kernel. lsof List open files. lspci List all PCI devices. lsusb List USB devices. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) M Command Description m4 Macro processor. mail Utility to compose, receive, send, forward, and reply to emails. mailq Shows to list all emails queued for delivery (sendmail queue). mailstats Shows current mail statistics. mailto Used to send mail with multimedia content in MIME format. make Utility to maintain groups of programs, recompile them if needed. makedbm Creates an NIS (Network Information Services) database map. makemap Creates database maps used by the keyed map lookups in sendmail. man Shows manual pages for Linux commands. manpath Determine search path for manual pages. mattrib Used to change MS-DOS file attribute flags. mbadblocks Checks MD-DOS filesystems for bad blocks. mcat Dump raw disk image. mcd Used to change MS-DOS directory. mcopy Used to copy MS-DOS files from or to Unix. md5sum Used to check MD5 checksum for a file. mdel, mdeltree Used to delete MS-DOS file. mdeltree recursively deletes MS-DOS directory and its contents. mdir Used to display an MS-DOS directory. mdu Used to display the amount of space occupied by an MS-DOS directory. merge Three-way file merge. Includes all changes from file2 and file3 to file1. mesg Allow/disallow osends to sedn write messages to your terminal. metamail For sending and showing rich text or multimedia email using MIME typing metadata. metasend An interface for sending non-text mail. mformat Used to add an MS-DOS filesystem to a low-level formatted floppy disk. mimencode Translate to/from MIME multimedia mail encoding formats. minfo Display parameters of an MS-DOS filesystem. mkdir Used to create directories. mkdosfs Used to create an MS-DOS filesystem under Linux. mke2fs Used create an ext2/ext3/ext4 filesystem. mkfifo Used to create named pipes (FIFOs) with the given names. mkfs Used to build a Linux filesystem on a hard disk partition. mkfs.ext3 Same as mke2fs, create an ext3 Linux filesystem. mkisofs Used to create an ISO9660/JOLIET/HFS hybrid filesystem. mklost+found Create a lost+found directory on a mounted ext2 filesystem. mkmanifest Makes alist of file names and their DOS 8.3 equivalent. mknod Create a FIFO, block (buffered) special file, character (unbuffered) special file with the specified name. mkraid Used to setup RAID device arrays. mkswap Set up a Linux swap area. mktemp Create a temporary file or directory. mlabel Make an MD-DOS volume label. mmd Make an MS-DOS subdirectory. mmount Mount an MS-DOS disk. mmove Move or rename an MS-DOS file or subdirectory. mmv Mass move and rename files. modinfo Show information about a Linux kernel module. modprobe Add or remove modules from the Linux kernel. more Display content of a file page-by-page. most Browse or page through a text file. mount Mount a filesystem. mountd NFS mount daemon. mpartition Used to report processor related statistics. mpstat Partition an MS-DOS disk. mpg123 Command-line mp3 player. mpg321 Similar to mpg123. mrd Remove an MS-DOS subdirectory. mren Rename an existing MS-DOS file. mshowfat Show FTA clusters allocated to a file. mt Control magnetic tape drive operation. mtools Utilities to access MS-DOS disks. mtoolstest Tests and displays the mtools configuration files. mtr A network diagnostic tool. mtype Display contents of an MS-DOS file. mv Move/rename files or directories. mzip Change protection mode and eject disk on Zip/Jaz drive. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) N Command Description named Internet domain name server. namei Follow a pathname until a terminal point is found. nameif Name network interfaces based on MAC addresses. nc Netcat utility. Arbitrary TCP and UDP connections and listens. netstat Show network information. newaliases Rebuilds mail alias database. newgrp Log-in to a new group. newusers Update/create new users in batch. nfsd Special filesystem for controlling Linux NFS server. nfsstat List NFS statistics. nice Run a program with modified scheduling priority. nl Show numbered line while displaying the contents of a file. nm List symbols from object files. nohup Run a command immune to hangups. notify-send A program to send desktop notifications. nslookup Used performs DNS queries. Read this article for more info. nsupdate Dynamic DNS update utility. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) O Command Description objcopy Copy and translate object files. objdump Display information from object files. od Dump files in octal and other formats. op Operator access, allows system administrators to grant users access to certain root operations that require superuser privileges. open Open a file using its default application. openvt Start a program on a new virtual terminal (VT). [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) P Command Description passwd Change user password. paste Merge lines of files. Write to standard output, TAB-separated lines consisting of sequentially corresponding lines from each file. patch Apply a patchfile (containing differences listing by diff program) to an original file. pathchk Check if file names are valid or portable. perl Perl 5 language interpreter. pgrep List process IDs matching the specified criteria among all the running processes. pidof Find process ID of a running program. ping Send ICMP ECHO_REQUEST to network hosts. pinky Lightweight finger. pkill Send kill signal to processes based on name and other attributes. pmap Report memory map of a process. popd Removes directory on the head of the directory stack and takes you to the new directory on the head. portmap Converts RPC program numbers to IP port numbers. poweroff Shuts down the machine. pppd Point-to-point protocol daemon. pr Convert (column or paginate) text files for printing. praliases Prints the current system mail aliases. printcap Printer capability database. printenv Show values of all or specified environment variables. printf Show arguments formatted according to a specified format. ps Report a snapshot of the current processes. ptx Produce a permuted index of file contents. pushd Appends a given directory name to the head of the stack and then cd to the given directory. pv Monitor progress of data through a pipe. pwck Verify integrity of password files. pwconv Creates shadow from passwd and an optionally existing shadow. pwd Show current directory. python Computer programming language often used to build websites and software, automate tasks, and conduct data analysis. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Q Command Description quota Shows disk usage, and space limits for a user or group. Without arguments, only shows user quotas. quotacheck Used to scan a file system for disk usage. quotactl Make changes to disk quotas. quotaoff Enable enforcement of filesystem quotas. quotaon Disable enforcement of filesystem quotas. quotastats Shows the report of quota system statistics gathered from the kernel. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) R Command Description raidstart Start/stop RAID devices. ram RAM disk device used to access the RAM disk in raw mode. ramsize Show usage information for the RAM disk. ranlib Generate index to the contents of an archive and store it in the archive. rar Create and manage RAR file in Linux. rarpd Respond to Reverse Address Resolution Protocol (RARP) requests. rcp Remote copy command to copy files between remote computers. rdate Set system date and time by fetching information from a remote machine. rdev Set or query RAM disk size, image root device, or video mode. rdist Remote file distribution client, maintains identical file copies over multiple hosts. rdistd Start the rdist server. read Read from a file descriptor. readarray Read lines from a file into an array variable. readcd Read/write compact disks. readelf Shows information about ELF (Executable and Linkable format) files. readlink Display value of a symbolic link or canonical file name. readonly Mark functions and variables as read-only. reboot Restart the machine. reject Accept/reject print jobs sent to a specified destination. remsync Synchronize remote files over email. rename Rename one or more files. renice Change priority of active processes. repquota Report disk usage and quotas for a specified filesystem. reset Reinitialize the terminal. resize2fs Used to resize ext2/ext3/ext4 file systems. restore Restore files from a backup created using dump. return Exit a shell function. rev Show contents of a file, reversing the order of characters in every line. rexec Remote execution client for exec server. rexecd Remote execution server. richtext View “richtext” on an ACSII terminal. rlogin Used to connect a local host system with a remote host. rlogind Acts as the server for rlogin.It facilitates remote login, and authentication based on privileged port numbers from trusted hosts. rm Removes specified files and directories (not by default). rmail Handle remote mail received via uucp. rmdir Used to remove empty directories. rmmod A program to remove modules from Linux kernel. rndc Name server control utility. Send command to a BIND DNS server over a TCP connection. rootflags Show/set flags for the kernel image. route Show/change IP routing table. routed A daemon, invoked at boot time, to manage internet routing tables. rpcgen An RPC protocol compiler. Parse a file written in the RPC language. rpcinfo Shows RPC information. Makes an RPC call to an RPC server and reports the findings. rpm A package manager for Linux distributions. Originally developed for RedHat Linux. rsh Remote shell. Connects to a specified host and executes commands. rshd A daemon that acts as a server for rsh and rcp commands. rsync A versitile to for copying files remotely and locally. runlevel Shows previous and current SysV runlevel. rup Remote status display. Shows current system status for all or specified hosts on the local network. ruptime Shows uptime and login details of the machines on the local network. rusers Shows the list of the users logged-in to the host or on all machines on the local network. rusersd The rsuerd daemon acts as a server that responds to the queries from rsuers command. rwall Sends messages to all users on the local network. rwho Reports who is logged-in to the hosts on the local network. rwhod Acts as a server for rwho and ruptime commands. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) S Command Description sane-find-scanner Find SCSI and USB scanner and determine their device files. sar Used to monitor Linux system’s resources like CPU usage, Memory utilization, I/O devices consumption, etc.. scanadf Retrieve multiple images from a scanner equipped with an automatic document feeder (ADF). scanimage Read images from image acquisition devices (scanner or camera) and display on standard output in PNM (Portable aNyMap) format. scp Copy files between hosts on a network securely using SSH. screen A window manager that enables multiple pseudo-terminals with the help of ANSI/VT100 terminal emulation. script Used to make a typescript of everything displayed on the screen during a terminal session. scriptreplay Used to replay a typescript/terminal_activity stored in the log file that was recorded by the script command. sdiff Shows two files side-by-side and highlights the differences. sed Stream editor for filtering and transforming text (from a file or a pipe input). select Synchronous I/O multiplexing. sendmail It’s a mail router or an MTA (Mail Transfer Agent). sendmail support can send a mail to one or more recipients using necessary protocols. sensors Shows the current readings of all sensor chips. seq Displays an incremental sequence of numbers from first to last. set Used to manipulate shell variables and functions. setfdprm Sets floppy disk parameters as provided by the user. setkeycodes Load kernel scancode-to-keycode mapping table entries. setleds Show/change LED light settings of the keyboard. setmetamode Define keyboard meta key handling. Without arguments, shows current meta key mode. setquota Set disk quotas for users and groups. setsid Run a program in a new session. setterm Set terminal attributes. sftp Secure File Transfer program. sh Command interpreter (shell) utility. sha1sum Compute and check 160-bit SHA1 checksum to verify file integrity. shift Shift positional parameters. shopt Shell options. showkey Examines codes sent by the keyboard displays them in printable form. showmount Shows information about NFS server mount on the host. shred Overwrite a file to hide its content (optionally delete it), making it harder to recover it. shutdown Power-off the machine. size Lists section size and the total size of a specified file. skill Send a signal to processes. slabtop Show kernel slab cache information in real-time. slattach Attack a network interface to a serial line. sleep Suspend execution for a specified amount of time (in seconds). slocate Display matches by searching filename databases. Takes ownership and file permission into consideration. snice Reset priority for processes. sort Sort lines of text files. source Run commands from a specified file. split Split a file into pieces of fixed size. ss Display socket statistics, similar to netstat. ssh An SSH client for logging in to a remote machine. It provides encrypted communication between the hosts. ssh-add Adds private key identities to the authentication agent. ssh-agent It holds private keys used for public key authentication. ssh-keygen It generates, manages, converts authentication keys for ssh. ssh-keyscan Gather ssh public keys. sshd Server for the ssh program. stat Display file or filesystem status. statd A daemon that listens for reboot notifications from other hosts, and manages the list of hosts to be notified when the local system reboots. strace Trace system calls and signals. strfile Create a random access file for storing strings. strings Search a specified file and prints any printable strings with at least four characters and followed by an unprintable character. strip Discard symbols from object files. stty Change and print terminal line settings. su Change user ID or become superuser. sudo Execute a command as superuser. sum Checksum and count the block in a file. suspend Suspend the execution of the current shell. swapoff Disable devices for paging and swapping. swapon Enable devices for paging and swapping. symlink Create a symbolic link to a file. sync Synchronize cached writes to persistent storage. sysctl Configure kernel parameters at runtime. sysklogd Linux system logging utilities. Provides syslogd and klogd functionalities. syslogd Read and log system messages to the system console and log files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) T Command Description tac Concatenate and print files in reverse order. Opposite of cat command. tail Show the last 10 lines of each specified file(s). tailf Follow the growth of a log file. (Deprecated command) talk A two-way screen-oriented communication utility that allows two user to exchange messages simultaneously. talkd A remote user communication server for talk . tar GNU version of the tar archiving utility. Used to store and extract multiple files from a single archive. taskset Set/retrieve a process’s CPU affinity. tcpd Access control utility for internet services. tcpdump Dump traffic on network. Displays a description of the contents of packets on a network interface that match the boolean expression. tcpslice Extract pieces of tcpdump files or merge them. tee Read from standard input and write to standard output and files. telinit Change SysV runlevel. telnet Telnet protocol user interface. Used to interact with another host using telnet. telnetd A server for the telnet protocol. test Check file type and compare values. tftp User interface to the internet TFTP (Trivial File Transfer Protocol). tftpd TFTP server. time Run programs and summarize system resource usage. timeout Execute a command with a time limit. times Shows accumulated user and system times for the shell and it’s child processes. tload Shows a graph of the current system load average to the specified tty. tmpwatch Recursively remove files and directories which haven’t been accessed for the specified period of time. top Displays real-time view of processes running on the system. touch Change file access and modification times. tput Modify terminal-dependent capabilities, color, etc. tr Translate, squeeze, or delete characters from standard input and display on standard output. tracepath Traces path to a network host discovering MTU (Maximum Transmission Unit) along this path. traceroute Traces the route taken by the packets to reach the network host. trap Trap function responds to hardware signals. It defines and creates handlers to run when the shell receives signals. tree A recursive directory listing program that produces a depth-indented listing of files. troff The troff processor of the groff text formatting system. TRUE Exit with a status code indicating success. tset Initialize terminal. tsort Perform topological sort. tty Display the filename of the terminal connected to standard input. tune2fs Adjust tuneable filesystem parameters on ext2/ext3/ext4 filesystems. tunelp Set various parameters for the line printer devices. type Write a description for a command type. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) U Command Description ul Underline text. ulimit Get and set user limits for the calling process. umask Set file mode creation mask. umount Unmount specified file systems. unalias Remove alias definitions for specified alias names. uname Show system information. uncompress Uncompress the files compressed with the compress command. unexpand Convert spaces to tabs for a specified file. unicode_start Put keyboard and console in Unicode mode. unicode_stop Revert keyboard and console from Unicode mode. uniq Report or omit repeating lines. units Convert units from one scalar to another. unix2dos Converts a Unix text file to DOS format. unrar Extract files from a RAR archive. unset Remove variable or function names. unshar Unpack shell archive scripts. until Execute command until a given condition is true. uptime Tell how long the system has been running. useradd Create a new user or update default user information. userdel Delete a user account and related files. usermod Modify a user account. username It provides a set of commands to fetch username and its configurations from the Linux host. users Show the list of active users on the machine. usleep Suspend execution for microsecond intervals. uudecode Decode a binary file. uuencode Encode a binary file. uuidgen Created a new UUID (Universally Unique Identifier) table. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) V Command Description vdir Same as ls -l -b . Verbosely list directory contents. vi A text editor utility. vidmode Set the video mode for a kernel image. Displays current mode value without arguments. Alternative: rdev -v vim Vi Improved, a text-based editor which is a successor to vi. vmstat Shows information about processes, memory, paging, block IO, traps, disks, and CPU activity. vnstat Used by system administrators in order to monitor network parameters such as bandwidth consumption or maybe some traffic flowing in or out. volname Returns volume name for a device formatted with an ISO-9660 filesystem. For example, CD-ROM. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) W Command Description w Show who is logged-on and what they’re doing. wait Waits for a specified process ID(s) to terminate and returns the termination status. wall Display a message on the terminals all the users who are currently logged-in. warnquota Send mail to the users who’ve exceeded their disk quota soft limit. watch Runs commands repeatedly until interrupted and shows their output and errors. wc Print newline, word, and byte count for each of the specified files. wget A non-interactive file download utility. whatis Display one line manual page descriptions. whereis Locate the binary, source, and man page files for a command. which For a given command, lists the pathnames for the files which would be executed when the command runs. while Conditionally execute commands (while loop). who Shows who is logged on. whoami Displays the username tied to the current effective user ID. whois Looks for an object in a WHOIS database write Display a message on other user’s terminal. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) X Command Description xargs Runs a command using initial arguments and then reads remaining arguments from standard input. xdg-open Used to open a file or URL in an application preferred by the user. xinetd Extended internet services daemon. Works similar to inetd. xz Compress/ Decompress .xz and .lzma files. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Y Command Description yacc Yet Another Compiler Compiler, a GNU Project parser generator. yes Repeatedly output a line with a specified string(s) until killed. ypbind A daemon that helps client processes to connect to an NIS server. ypcat Shows the NIS map (or database) for the specified MapName parameter. ypinit Sets up NIS maps on an NIS server. ypmatch Shows values for specified keys from an NIS map. yppasswd Change NIS login password. yppasswdd Acts as a server for the yppasswd command. Receives and executes requests. yppoll Shows the ID number or version of NIS map currently used on the NIS server. yppush Forces slave NIS servers to copy updated NIS maps. ypserv A daemon activated at system startup. It looks for information in local NIS maps. ypset Point a client (running ypbind) to a specific server (running ypserv). yptest Calls various functions to check the configuration of NIS services. ypwhich Shows the hostname for NIS server or master server for a given map. ypxfr Transfers NIS server map from server to a local host. [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Z Command Description zcat Used to compress/uncompress files. Similar to gzip zcmp Compare compressed files. zdiff Compare compressed files line by line. zdump Displays time for the timezone mentioned. zforce Adds .gz extension to all gzipped files. zgrep Performs grep on compressed files. zic Creates time conversion information files using the specified input files. zip A file compression and packaging utility. zless Displays information of a compressed file (using less command) on the terminal one screen at a time. zmore Displays output of a compressed file (using more command) on the terminal one page at a time. znew Recompress .z files to .gz. files. Credits: fossbytes & geeksforgeeks [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table) Quick cheat sheet 📝 >**Note** > Examples like `-a|--all` option flags means, single `-` used for _short_ option(-a) **or**| double `--` used for _long_ option(--all). Both was added for educational purpose.### Contents- [Command Information](#command-information)- [Command History](#command-history)- [Navigating Directories](#navigating-directories)- [Creating Directories](#creating-directories)- [Moving Directories](#moving-directories)- [Deleting Directories](#deleting-directories)- [Creating Files](#creating-files)- [Standard Output, Error and Input](#standard-output-standard-error-and-standard-input)- [Moving Files](#moving-files)- [Deleting Files](#deleting-files)- [Reading Files](#reading-files)- [File Permissions](#file-permissions)- [Finding Files](#finding-files)- [Find in Files](#find-in-files)- [Replace in Files](#replace-in-files)- [Symbolic Links](#symbolic-links)- [Compressing Files](#compressing-files)- [Decompressing Files](#decompressing-files)- [Packages](#packages)- [Disk Usage](#disk-usage)- [Memory Usage](#memory-usage)- [Shutdown and Reboot](#shutdown-and-reboot)- [Identifying Processes](#identifying-processes)- [Process Priority](#process-priority)- [Killing Processes](#killing-processes)- [Date & Time](#date--time)- [Scheduled Tasks](#scheduled-tasks)- [User Mangement](#user-management)- [HTTP Requests](#http-requests)- [Network Troubleshooting](#network-troubleshooting)- [DNS](#dns)- [Hardware](#hardware)- [System Information](#system-information)- [Terminal Multiplexers](#terminal-multiplexers)- [Secure Shell Protocol (SSH)](#secure-shell-protocol-ssh)- [Secure Copy](#secure-copy)- [Bash Profile](#bash-profile)- [Bash Script](#bash-script)### Command Information```bashman chmod # Display page manual of a commandman -f|--whatis chmod # Display short description about a commandman -k|--apropos permission # Display all related commands from a specific keywordchmod --help # Display usage options of a command```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Command History```bashhistory # View all previous commandshistory | grep foo # View the commands using a specific wordhistory | grep -E|--extended-regexp -i|--ignore-case 'foo1|foo2|foo3' # View the commands using more than 1 specific word(case sensitive)history | head -n|--lines 3 # View the first 3 executed commandshistory 3 # View the last 3 executed commandshistory -d 99 # Clear a command from a specific line history -c # Clears all history commands!! # Run the last command executedtouch foo.sh # <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<┐chmod +x !$ # !$ is the last argument of the last command i.e. foo.sh <<<<┘```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Navigating Directories```bashpwd # Print current directory pathls # List directoriesls -a|--all # List directories including hiddenls -l # List directories in long formls -l -h|--human-readable # List directories in long form with human readable sizesls -t # List directories by modification time, newest firststat foo.txt # List size, created and modified timestamps for a filestat foo # List size, created and modified timestamps for a directorytree # List directory and file treetree -a # List directory and file tree including hiddentree -d # List directory treecd foo # Go to foo sub-directorycd # Go to home directorycd ~ # Go to home directorycd - # Go to last directorypushd foo # Go to foo sub-directory and add previous directory to stackpopd # Go back to directory in stack saved by `pushd````[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Creating Directories ```bashmkdir foo # Create a directorymkdir foo bar # Create multiple directoriesmkdir -p|--parents foo/bar # Create nested directorymkdir -p|--parents {foo,bar}/baz # Create multiple nested directoriesmktemp -d|--directory # Create a temporary directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Moving Directories```bashcp -R|--recursive foo bar # Copy directorymv foo bar # Move directoryrsync -z|--compress -v|--verbose /foo /bar # Copy directory, overwrites destinationrsync --ignore-existing -a|--archive-a|--archive -z|--compress -v|--verbose /foo /bar # Copy directory, without overwriting destinationrsync -avz /foo username@hostname:/bar # Copy local directory to remote directoryrsync -avz username@hostname:/foo /bar # Copy remote directory to local directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Deleting Directories```bashrmdir foo # Delete non-empty directoryrm -r|--recursive foo # Delete directory including contentsrm -r|--recursive -f|--force foo # Delete directory including contents, ignore nonexistent files and never prompt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Creating Files```bashtouch foo.txt # Create file or update existing files modified timestamptouch foo.txt bar.txt # Create multiple filestouch {foo,bar}.txt # Create multiple filestouch test{1..3} # Create test1, test2 and test3 filestouch test{a..c} # Create testa, testb and testc filesmktemp # Create a temporary file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Standard Output, Standard Error and Standard Input```bashecho "foo" > bar.txt # Overwrite file with contentecho "foo" >> bar.txt # Append to file with contentls exists 1> stdout.txt # Redirect the standard output to a filels noexist 2> stderror.txt # Redirect the standard error output to a filels > out.txt 2>&1 # Redirect standard output and error to a filels > /dev/null # Discard standard output and errorread foo # Read from standard input and write to the variable foo```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Moving Files```bashcp foo.txt bar.txt # Copy filemv foo.txt bar.txt # Move filersync -z|--compress -v|--verbose /foo.txt /bar # Copy file quickly if not changedrsync -z|--compress -v|--verbose /foo.txt /bar.txt # Copy and rename file quickly if not changed```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Deleting Files```bashrm foo.txt # Delete filerm -f|--force foo.txt # Delete file, ignore nonexistent files and never prompt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Reading Files```bashcat foo.txt # Print all contentsless foo.txt # Print some contents at a time (g - go to top of file, SHIFT+g, go to bottom of file, /foo to search for 'foo')head foo.txt # Print top 10 lines of filetail foo.txt # Print bottom 10 lines of filetail -f foo.txt # Print bottom 10 lines of file updating with new dataopen foo.txt # Open file in the default editorwc foo.txt # List number of lines words and characters in the file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## File Permissions| # | Permission | rwx | Binary || - | - | - | - || 7 | read, write and execute | rwx | 111 || 6 | read and write | rw- | 110 || 5 | read and execute | r-x | 101 || 4 | read only | r-- | 100 || 3 | write and execute | -wx | 011 || 2 | write only | -w- | 010 || 1 | execute only | --x | 001 || 0 | none | --- | 000 |For a directory, execute means you can enter a directory.| User | Group | Others | Description || - | - | - | - || 6 | 4 | 4 | User can read and write, everyone else can read (Default file permissions) || 7 | 5 | 5 | User can read, write and execute, everyone else can read and execute (Default directory permissions) |- u - User- g - Group- o - Others- a - All of the above```bashls -l /foo.sh # List file permissionschmod +100 foo.sh # Add 1 to the user permissionchmod -100 foo.sh # Subtract 1 from the user permissionchmod u+x foo.sh # Give the user execute permissionchmod g+x foo.sh # Give the group execute permissionchmod u-x,g-x foo.sh # Take away the user and group execute permissionchmod u+x,g+x,o+x foo.sh # Give everybody execute permissionchmod a+x foo.sh # Give everybody execute permissionchmod +x foo.sh # Give everybody execute permission```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Finding FilesFind binary files for a command.```bashtype -a wget # Display all locations of executablewhich -a wget # Display all locations of executables whereis wget # Find the binary, source, and manual page files````locate` uses an index and is fast.```bashupdatedb # Update the indexlocate foo.txt # Find a filelocate --ignore-case # Find a file and ignore caselocate f*.txt # Find a text file starting with 'f'````find` doesn't use an index and is slow.```bashfind /path -name foo.txt # Find a filefind /path -iname foo.txt # Find a file with case insensitive searchfind /path -name "*.txt" # Find all text filesfind /path -name foo.txt -delete # Find a file and delete itfind /path -name "*.png" -exec pngquant {} # Find all .png files and execute pngquant on itfind /path -type f -name foo.txt # Find a filefind /path -type d -name foo # Find a directoryfind /path -type l -name foo.txt # Find a symbolic linkfind /path -type f -mtime +30 # Find files that haven't been modified in 30 daysfind /path -type f -mtime +30 -delete # Delete files that haven't been modified in 30 days```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Find in Files```bashgrep 'foo' /bar.txt # Search for 'foo' in file 'bar.txt'grep 'foo' /bar -r|--recursive # Search for 'foo' in directory 'bar'grep 'foo' /bar -R|--dereference-recursive # Search for 'foo' in directory 'bar' and follow symbolic linksgrep 'foo' /bar -l|--files-with-matches # Show only files that matchgrep 'foo' /bar -L|--files-without-match # Show only files that don't matchgrep 'Foo' /bar -i|--ignore-case # Case insensitive searchgrep 'foo' /bar -x|--line-regexp # Match the entire linegrep 'foo' /bar -C|--context 1 # Add N line of context above and below each search resultgrep 'foo' /bar -v|--invert-match # Show only lines that don't matchgrep 'foo' /bar -c|--count # Count the number lines that matchgrep 'foo' /bar -n|--line-number # Add line numbersgrep 'foo' /bar --colour # Add colour to outputgrep 'foo\|bar' /baz -R # Search for 'foo' or 'bar' in directory 'baz'grep --extended-regexp|-E 'foo|bar' /baz -R # Use regular expressionsgrep -E 'foo|bar' /baz -R # Use regular expressions```### Replace in Files```bashsed 's/fox/bear/g' foo.txt # Replace fox with bear in foo.txt and output to consolesed 's/fox/bear/gi' foo.txt # Replace fox (case insensitive) with bear in foo.txt and output to consolesed 's/red fox/blue bear/g' foo.txt # Replace red with blue and fox with bear in foo.txt and output to consolesed 's/fox/bear/g' foo.txt > bar.txt # Replace fox with bear in foo.txt and save in bar.txtsed 's/fox/bear/g' foo.txt -i|--in-place # Replace fox with bear and overwrite foo.txt```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Symbolic Links```bashln -s|--symbolic foo bar # Create a link 'bar' to the 'foo' folderln -s|--symbolic -f|--force foo bar # Overwrite an existing symbolic link 'bar'ls -l # Show where symbolic links are pointing```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Compressing Files### zipCompresses one or more files into *.zip files.```bashzip foo.zip /bar.txt # Compress bar.txt into foo.zipzip foo.zip /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.zipzip foo.zip /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.zipzip -r|--recurse-paths foo.zip /bar # Compress directory bar into foo.zip```### gzipCompresses a single file into *.gz files.```bashgzip /bar.txt foo.gz # Compress bar.txt into foo.gz and then delete bar.txtgzip -k|--keep /bar.txt foo.gz # Compress bar.txt into foo.gz```### tar -cCompresses (optionally) and combines one or more files into a single *.tar, *.tar.gz, *.tpz or *.tgz file.```bashtar -c|--create -z|--gzip -f|--file=foo.tgz /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.tgztar -c|--create -z|--gzip -f|--file=foo.tgz /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.tgztar -c|--create -z|--gzip -f|--file=foo.tgz /bar # Compress directory bar into foo.tgz```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Decompressing Files### unzip```bashunzip foo.zip # Unzip foo.zip into current directory```### gunzip```bashgunzip foo.gz # Unzip foo.gz into current directory and delete foo.gzgunzip -k|--keep foo.gz # Unzip foo.gz into current directory```### tar -x```bashtar -x|--extract -z|--gzip -f|--file=foo.tar.gz # Un-compress foo.tar.gz into current directorytar -x|--extract -f|--file=foo.tar # Un-combine foo.tar into current directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Packages```bashapt update # Refreshes repository indexapt search wget # Search for a packageapt show wget # List information about the wget packageapt list --all-versions wget # List all versions of the packageapt install wget # Install the latest version of the wget packageapt install wget=1.2.3 # Install a specific version of the wget packageapt remove wget # Removes the wget packageapt upgrade # Upgrades all upgradable packagesapt clean # Clears out the local repository of downloaded package filesdpkg -i|--install package_name.deb # Install deb filerpm -i|--install package_name.rpm # Install rpm file ```### Install package source code```bashtar zxvf sourcecode.tar.gzcd sourcecode./configuremakemake install```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Disk Usage```bashdf # List disks, size, used and available spacedf -h|--human-readable # List disks, size, used and available space in a human readable formatdu # List current directory, subdirectories and file sizesdu /foo/bar # List specified directory, subdirectories and file sizesdu -h|--human-readable # List current directory, subdirectories and file sizes in a human readable formatdu -d|--max-depth # List current directory, subdirectories and file sizes within the max depthdu -d 0 # List current directory size```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Memory Usage```bashfree # Show memory usagefree -h|--human # Show human readable memory usagefree -h|--human --si # Show human readable memory usage in power of 1000 instead of 1024free -s|--seconds 5 # Show memory usage and update continuously every five seconds```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Shutdown and Reboot```bashshutdown # Shutdown in 1 minuteshutdown now # Immediately shut downshutdown +5 # Shutdown in 5 minutesshutdown -r|--reboot # Reboot in 1 minuteshutdown -r|--reboot now # Immediately rebootshutdown -r|--reboot +5 # Reboot in 5 minutesshutdown -c # Cancel a shutdown or rebootreboot # Reboot nowreboot -f # Force a reboot```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Identifying Processes```bashtop # List all processes interactivelyhtop # List all processes interactivelyps ax # List all processespidof foo # Return the PID of all foo processesCTRL+Z # Suspend a process running in the foregroundbg # Resume a suspended process and run in the backgroundfg # Bring the last background process to the foregroundfg 1 # Bring the background process with the PID to the foregroundsleep 30 & # Sleep for 30 seconds and move the process into the backgroundjobs # List all background jobsjobs -p # List all background jobs with their PIDlsof # List all open files and the process using themlsof -itcp:4000 # Return the process listening on port 4000```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Process PriorityProcess priorities go from -20 (highest) to 19 (lowest).```bashnice -n -20 foo # Change process priority by namerenice 20 PID # Change process priority by PIDps -o ni PID # Return the process priority of PID```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Killing Processes```bashCTRL+C # Kill a process running in the foregroundkill PID # Shut down process by PID gracefully. Sends TERM signal.kill -9 PID # Force shut down of process by PID. Sends SIGKILL signal.pkill foo # Shut down process by name gracefully. Sends TERM signal.pkill -9 foo # force shut down process by name. Sends SIGKILL signal.killall foo # Kill all process with the specified name gracefully.```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Date & Time```bashdate # Print the date and timedate --iso-8601 # Print the ISO8601 datedate --iso-8601=ns # Print the ISO8601 date and timedate -s "02 DEC 2020 12:02:02" # Manually change date and timedpkg-reconfigure tzdata # Change date/timezoneuptime # Print how long the system has been runningtime tree # Print amount of time to tree takes to execute```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Scheduled Tasks```pre * * * * *Minute, Hour, Day of month, Month, Day of the week``````bashcrontab -l # List cron tabcrontab -e # Edit cron tab in Vimcrontab /path/crontab # Load cron tab from a filecrontab -l > /path/crontab # Save cron tab to a file* * * * * foo # Run foo every minute*/15 * * * * foo # Run foo every 15 minutes0 * * * * foo # Run foo every hour15 6 * * * foo # Run foo daily at 6:15 AM44 4 * * 5 foo # Run foo every Friday at 4:44 AM0 0 1 * * foo # Run foo at midnight on the first of the month0 0 1 1 * foo # Run foo at midnight on the first of the yearat -l # List scheduled tasksat -c 1 # Show task with ID 1at -r 1 # Remove task with ID 1at now + 2 minutes # Create a task in Vim to execute in 2 minutesat 12:34 PM next month # Create a task in Vim to execute at 12:34 PM next monthat tomorrow # Create a task in Vim to execute tomorrow```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## User Management```bashsudo su # switch to root usersudo foo # execute command as the root usersu username # switch to a different useradduser username # To add a new userpasswd -l|--lock username # To change the password of a useruserdel username # To remove useruserdel -r|--remove username # To remove user with home directory and mail spoolusermod -a|--append -G|--groups GROUPNAME USERNAME # To add a user to a groupdeluser USER GROUPNAME # To remove a user from a grouplast # Shows information of all the users logged inlast username # Gives information of a particular user```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## HTTP Requests```bashcurl https://example.com # Return response bodycurl -i|--include https://example.com # Include status code and HTTP headerscurl -L|--location https://example.com # Follow redirectscurl -O|--remote-name foo.txt https://example.com # Output to a text filecurl -H|--header "User-Agent: Foo" https://example.com # Add a HTTP headercurl -X|--request POST -H "Content-Type: application/json" -d|--data '{"foo":"bar"}' https://example.com # POST JSONcurl -X POST -H --data-urlencode foo="bar" http://example.com # POST URL Form Encodedwget https://example.com/file.txt # Download a file to the current directorywget -O|--output-document foo.txt https://example.com/file.txt # Output to a file with the specified name```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Network Troubleshooting```bashping example.com # Send multiple ping requests using the ICMP protocolping -c 10 -i 5 example.com # Make 10 attempts, 5 seconds apartip addr # List IP addresses on the systemip route show # Show IP addresses to routercurl ifconfig.me # Obtain external IP addressnetstat -i|--interfaces # List all network interfaces and in/out usagenetstat -l|--listening # List all open portstraceroute example.com # List all servers the network traffic goes throughmtr -w|--report-wide example.com # Continually list all servers the network traffic goes throughmtr -r|--report -w|--report-wide -c|--report-cycles 100 example.com # Output a report that lists network traffic 100 timesnmap 0.0.0.0 # Scan for the 1000 most common open ports on localhostnmap 0.0.0.0 -p1-65535 # Scan for open ports on localhost between 1 and 65535nmap 192.168.4.3 # Scan for the 1000 most common open ports on a remote IP addressnmap -sP 192.168.1.1/24 # Discover all machines on the network by ping'ing them```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## DNS```bashdig example.com # Show query information of domain A recordsdig -4 example.com # Show IPv4 A recordsdig -6 example.com # Show IPv6 AAA recordsdig example.com @nameserver # Show query of a specific nameserverdig example.com -p 123 # Show query of a specific port numbercat /etc/resolv.conf # Nameservers filecat /etc/systemd/resolved.conf # DNS resolver config file```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Hardware```bashlsusb # List USB deviceslspci # List PCI hardwarelshw # List all hardware```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## System Information```bashuname -s # Print kernel nameuname -r # Print kernel releaseuname -m # Print Architectureuname -o # Print Operating System```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Terminal MultiplexersStart multiple terminal sessions. Active sessions persist reboots. `tmux` is more modern than `screen`.```bashtmux # Start a new session (CTRL-b + d to detach)tmux ls # List all sessionstmux attach -t 0 # Reattach to a sessionscreen # Start a new session (CTRL-a + d to detach)screen -ls # List all sessionsscreen -R 31166 # Reattach to a sessionexit # Exit a session```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Secure Shell Protocol (SSH)```bashssh hostname # Connect to hostname using your current user name over the default SSH port 22ssh -i foo.pem hostname # Connect to hostname using the identity filessh user@hostname # Connect to hostname using the user over the default SSH port 22ssh user@hostname -p 8765 # Connect to hostname using the user over a custom portssh ssh://user@hostname:8765 # Connect to hostname using the user over a custom port```Set default user and port in `~/.ssh/config`, so you can just enter the name next time:```bash$ cat ~/.ssh/configHost name User foo Hostname 127.0.0.1 Port 8765$ ssh name```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Secure Copy```bashscp foo.txt ubuntu@hostname:/home/ubuntu # Copy foo.txt into the specified remote directoryscp ubuntu@hostname:/home/ubuntu/foo.txt /C:\Users\Admin # Copy foo.txt from the specified remote directory```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Bash Profile- bash - `.bashrc`- zsh - `.zshrc````bash# Always run ls after cdfunction cd { builtin cd "$@" && ls}# Prompt user before overwriting any filesalias cp='cp --interactive'alias mv='mv --interactive'alias rm='rm --interactive'# Always show disk usage in a human readable formatalias df='df -h'alias du='du -h'```[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents)## Bash Script### Variables```bash#!/bin/bashfoo=123 # Initialize variable foo with 123declare -i foo=123 # Initialize an integer foo with 123declare -r foo=123 # Initialize readonly variable foo with 123echo $foo # Print variable fooecho ${foo}_'bar' # Print variable foo followed by _barecho ${foo:-'default'} # Print variable foo if it exists otherwise print defaultexport foo # Make foo available to child processesunset foo # Make foo unavailable to child processes and current session```### Environment Variables```bash#!/bin/bashset # List all environment variablesecho $PATH # Print PATH environment variableexport FOO=Bar # Set an environment variable```### Functions```bash#!/bin/bashgreet() { local world="World" echo "$1 $world" return "$1 $world"}greet "Hello"greeting=$(greet "Hello")```### Exit Codes```bash#!/bin/bashexit 0 # Exit the script successfullyexit 1 # Exit the script unsuccessfullyecho $? # Print the last exit code```### Conditional Statements#### Boolean Operators- `$foo` - Is true- `!$foo` - Is false#### Numeric Operators- `-eq` - Equals- `-ne` - Not equals- `-gt` - Greater than- `-ge` - Greater than or equal to- `-lt` - Less than- `-le` - Less than or equal to- `-e` foo.txt - Check file exists- `-z` foo - Check if variable exists#### String Operators- `=` - Equals- `==` - Equals- `-z` - Is null- `-n` - Is not null- `<` - Is less than in ASCII alphabetical order- `>` - Is greater than in ASCII alphabetical order#### If Statements```bash#!/bin/bash[[if [[$foo = 'bar']]; then echo 'one'elif [[$foo = 'bar']] || [[$foo = 'baz']]; then echo 'two'elif [[$foo = 'ban']] && [[$USER = 'bat']]; then echo 'three'else echo 'four'fi]]```#### Inline If Statements```bash#!/bin/bash[[ $USER = 'rehan' ]] && echo 'yes' || echo 'no'```#### While Loops```bash#!/bin/bash[declare -i countercounter=10while [$counter -gt 2]; do echo The counter is $counter counter=counter-1done]```#### For Loops```bash#!/bin/bashfor i in {0..10..2} do echo "Index: $i" donefor filename in file1 file2 file3 do echo "Content: " >> $filename donefor filename in *; do echo "Content: " >> $filename done```#### Case Statements```bash#!/bin/bashecho "What's the weather like tomorrow?"read weathercase $weather in sunny | warm ) echo "Nice weather: " $weather ;; cloudy | cool ) echo "Not bad weather: " $weather ;; rainy | cold ) echo "Terrible weather: " $weather ;; * ) echo "Don't understand" ;;esac``` Inspired by RehanSaeed/Bash-Cheat-Sheet [⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴄᴏɴᴛᴇɴᴛꜱ](#contents) Special characters 🔣 Char. Description ~ Home directory [tilde]. The path to a user's home directory location. - Previous directory [dash]. Go back to previous directory. / Filename path separator [forward slash]. Separates the components of a filename. It also represents the path to root directory. \ Escape [backslash]. A quoting mechanism for single characters. It preserves the literal value of the next character that follows, with the exception of newline. │ Pipe. It passes the output (stdout) of a previous command to the input (stdin) of the next one, or to the shell. This is a method of chaining commands together. || The OR operator is used to chain commands. It will execute succeeded commands which follows and stops if the preceding command fails. && The AND operator is used to chain commands. It will execute commands only if the first command is successful ; Command separator [semicolon]. Used to separate multiple commands and execute all the ones that is successful. & Run job in background[and]. A command followed by an & will run in the background. # Comment [number sign]. Lines in files beginning with a # (with the exception of #!) are comments and will not be executed. >, >>, < Redirect a command's output or input into a file. >| Force redirection (even if the noclobber option is set). This will forcibly overwrite an existing file. ' ' Single quotes protects the text inside them so that it has a literal meaning. This is a stronger form of quoting than double quotes. " " Whitespace. This is a tab, newline, vertical tab, form feed, carriage return, or space. Bash uses whitespace to determine where words begin and end. ! Reverse (or negate) [exclamation]. The ! operator inverts the exit status of the command to which it is applied. It also inverts the meaning of a test operator. * Wild card [asterisk]. The * character serves as a "wild card" for filename expansion in globbing . By itself, it matches every filename in a given directory. ? Wild card [question mark]. The ? character serves as a single-character "wild card" for filename expansion in globbing, as well as representing one character in an extended regular expression. { } Inline group [curly brackets]. Commands inside the curly braces are treated as if they were one command. It is convenient to use these when Bash syntax requires only one command and a function doesn't feel warranted. ( ) Subshell group [bracket].Commands within are executed in a subshell (a new process) Used much like a sandbox, if a command causes side effects (like changing variables), it will have no effect on the current shell. [ ] Test expression between [ ]. It is part of the shell builtin test. [[ ]] Test expression between [[ ]]. It is more flexible than the single-bracket [ ] test. (( )) Integer expansion. Expand and evaluate integer expression. ;; Terminator in a case option [double semicolon]. ,, , Lowercase conversion in parameter substitution. ^, ^^ Uppercase conversion in parameter substitution. Keyboard controls ⌨️ | Key | Function || :--: | :-- || Ctrl+a | Moves cursor to beginning of text in line || Ctrl+e | Moves cursor to end of text in line || Ctrl+b | Moves cursor backward one character position || Ctrl+f | Moves cursor forward one character position || Ctrl+u | Erase a line of input from cursor right to left of line || Ctrl+k | Erase a line of input from cursor left to right of line || Ctrl+d | Erase character forward from cursor left to right || Ctrl+h | Erase character backward from cursor right to left || Ctrl+w | Erase backwards to first non-alphanumeric character or empty space || Ctrl+p | Fetch previous command from history list || Ctrl+n | Fetch next command from history list || Ctrl+y | Fetch back command previously erased || Ctrl+t | Reverses the position of the character the cursor is on with the previous character || Ctrl+r | Reverse search commands from history list || Ctrl+z | Pauses a foreground job || Ctrl+c | Break/Terminate a foreground job || Ctrl+m | Clear the current line || Ctrl+o | Accept the current line for execution and fetch the next command || Ctrl+l | Clear screen contents (command-line needs to be empty) || Ctrl+s | Suspend || Ctrl+q | Resume || Ctrl+d | Log out from a shell (similar to exit) || | || | || | || Alt+b | Moves cursor one word backwards || Alt+f | Moves cursor one word forward || Alt+d | Erase the next word from cursor left to right || Alt+t | Reverses the position of the word the cursor is in with the previous word || Alt+u | Capitalizes every character from cursor left to right to the end of one word || Alt+l | UnCapitalizes every character from cursor left to right to the end of one word || Alt+r | Reverts any changes to a previously executed command that is edited || Alt+. | Fetch and paste the last word at end of a command from previous commands | Online Cheat Sheet :feelsgood: for quick references of commands and codes cheat.sh Terminal :```bashcurl cht.sh/keyword or curl cheat.sh/keyword``` Browser : https://cht.sh/ keyword or https://cheat.sh/ keyword # #### Offline usage Install cheat script manually Install globally(all users) : bashcurl -s https://cht.sh/:cht.sh | sudo tee /usr/local/bin/cht.sh && sudo chmod +x /usr/local/bin/cht.sh Run :```bashcht.sh keyword ``` To restore the repository download the bundle wget https://archive.org/download/github.com-trinib-Linux-Bash-Commands_-_2022-11-08_23-53-09/trinib-Linux-Bash-Commands_-_2022-11-08_23-53-09.bundle and run: git clone trinib-Linux-Bash-Commands_-_2022-11-08_23-53-09.bundle Source: https://github.com/trinib/Linux-Bash-Commands Uploader: trinib Upload date: 2022-11-08

In this episode: wrap-up of The Linux Link Tech Show Episode 155; listener feedback; three Listener Tips; a discussion of various helpful shell commands, including head , tail , find ( more on find at Linux.com), locate , ifconfig , iwconfig , ps , top , grep , adduser , passwd , and how to send a process to the background.

123

A macromedia file that shows basic Linux commands with short voice-overs. There are mp3's and jpg's in the cast.

Are you a new GNU/Linux user who wants to learn more than just dragging windows around and clicking your mouse? This book is designed for users who are completely new to the GNU/Linux command line and want to learn the fundamentals. In this book, basic Linux commands for navigation, file and directory administration, software installation, and elementary system troubleshooting are covered. You will discover how to use Linux commands in this book. Over the years, Linux has seen significant transformation and is currently regarded as one of the top operating systems in the world. As a system administrator, you maintain the functionality of the global computing infrastructure. Problems must be fixed, systems must be maintained, and security must be maintained at all times. I hope these commands will be useful and enable you to perform your work more effectively.

Linux Commands

An approachable manual for new and experienced programmers that introduces the programming languages C, C++, Java, and Python. This book is for all programmers, whether you are a novice or an experienced pro. It is designed for an introductory course that provides beginning engineering and computer science students with a solid foundation in the fundamental concepts of computer programming. It also offers valuable perspectives on important computing concepts through the development of programming and problem-solving skills using the languages C, C++, Java, and Python. The beginner will find its carefully paced exercises especially helpful. Of course, those who are already familiar with programming are likely to derive more benefits from this book. After reading this book you will find yourself at a moderate level of expertise in C, C++, Java and Python, from which you can take yourself to the next levels. The command-line interface is one of the nearly all well built trademarks of Linux. There exists an ocean of Linux commands, permitting you to do nearly everything you can be under the impression of doing on your Linux operating system. However, this, at the end of time, creates a problem: because of all of so copious commands accessible to manage, you don't comprehend where and at which point to fly and learn them, especially when you are a learner. If you are facing this problem, and are peering for a painless method to begin your command line journey in Linux, you've come to the right place-as in this book, we will launch you to a hold of well liked and helpful Linux commands. This book gives a thorough introduction to the C, C++, Java, and Python programming languages, covering everything from fundamentals to advanced concepts. It also includes various exercises that let you put what you learn to use in the real world.

The Linux Commands Handbook follows the 80/20 rule: learn in 20% of the time the 80% of a topic. I find this approach gives a well-rounded overview. This book does not try to cover everything under the sun related to Linux and its commands. It focuses on the small core commands that you will use the 80% or 90% of the time, trying to simplify the usage of the more complex ones. All those commands work on Linux, macOS, WSL, and anywhere you have a UNIX environment. I hope the contents of this book will help you achieve what you want: get comfortable with Linux. This book is written by Flavio. I publish programming tutorials every day on my website flaviocopes.com. You can reach me on Twitter @flaviocopes. Enjoy!

Linux Commands Cook Book 

Compilation of One Day One Command ilugc kanchilug mailing thread

Learning Linux | rm and rmdir Commands Hello Everyone, Today's Learning Linux Series, offers you the opportunity so we can show you how to use the rm and rmdir commands. - What is the difference between rmdir and rm ? rmdir: can only be used to remove an empty directory. It will not work for non-empty directories. rm: removes both files and non-empty directories with an extra option. For example, you create a directory called test with the command mkdir test. You don't create any files in that directory and later on, you decide to remove it. If so, you can normally use rmdir test. If you have created files inside the test directory and we want to remove both the test directory and files inside the test you have to enter rm -r test/ An even faster solution is rm -rf, which removes recursively and forcefully all files in a directory and the directory itself. In this tutorial, we are going to show you the basic usage of this tool using easy to understand examples. The faster you are, the more knowledge you have of the linux operating system, in combination with offensive security, WILL make you become stronger and more effective. If you are new to Linux, it's worth knowing that command line is a very powerful tool, capable of doing almost all those tasks that you can do through the graphical interface. We hope you enjoy the Tutorial. Disclaimer : This Video is for Educational Purpose Only, what you do is your responsibility and Black Hat Ethical Hacking or anyone involved, is not held accounted for if any damage for any reason occurs . Sound Track: ROYALTY FREE "Hiding Your Reality" Kevin MacLeod (incompetech.com) Licensed under Creative Commons: By Attribution 3.0 License http://creativecommons.org/licenses/by/3.0/ "Hitman" Kevin MacLeod (incompetech.com) Licensed under Creative Commons: By Attribution 3.0 License http://creativecommons.org/licenses/by/3.0/ -------------------------- Follow us Online: Facebook: https://www.facebook.com/secur1ty1samyth Twitter: https://twitter.com/secur1ty1samyth Instagram: https://www.instagram.com/blackhatethicalhacking Linked In: https://www.linkedin.com/company/black-hat-ethical-hacking Github: https://github.com/blackhatethicalhacking Support our work on Patreon: https://www.patreon.com/blackhatethicalhacking -------------------------- Source: https://www.youtube.com/watch?v=mFseik6gx90 Uploader: Black Hat Ethical Hacking

LinuX Commands

xiv, 462 p. ; 22 cm

xiv, 462 p. ; 22 cm

xiv, 462 p. ; 22 cm

In this shortened episode: upcoming episodes on file managers and Fedora Core 6; interview with Patrick Volkerding on The Linux Link Tech Show ; a discussion of various Linux commands including df , wc , cal , date , clear , who , whoami , whois , whereis , cat , lpr , lpstat , and lpq ; promo for the Gadgetboyz podcast ; a Listener Tip on GParted Live CD ; listener feedback.

Linux commands 20th Anniversary release

Linux commands 20th Anniversary release

Learn about Linux commands, such as ping, traceroute, and netstat in this episode of HakTip! ------------------------------- Shop: http://www.hakshop.com Support: http://www.patreon.com/threatwire Subscribe: http://www.youtube.com/hak5 Our Site: http://www.hak5.org Contact Us: http://www.twitter.com/hak5 Threat Wire RSS: https://shannonmorse.podbean.com/feed/ Threat Wire iTunes: https://itunes.apple.com/us/podcast/threat-wire/id1197048999 Help us with Translations! http://www.youtube.com/timedtext_cs_panel?tab=2&c=UC3s0BtrBJpwNDaflRSoiieQ ------------------------------ https://www.hak5.org/episodes/haktip-125 http://www.tecmint.com/20-netstat-commands-for-linux-network-management/ -~-~~-~~~-~~-~- Please watch: "Bash Bunny Primer - Hak5 2225" https://www.youtube.com/watch?v=8j6hrjSrJaM -~-~~-~~~-~~-~- Source: https://www.youtube.com/watch?v=F1geJWP4Yvs Uploader: Hak5

------------------------------- Shop: http://www.hakshop.com Support: http://www.patreon.com/threatwire Subscribe: http://www.youtube.com/hak5 Our Site: http://www.hak5.org Contact Us: http://www.twitter.com/hak5 ------------------------------ In this episode of Hak5, we break into some linux BASH commands that we favor, plus some hilarious easter eggs. -~-~~-~~~-~~-~- Please watch: "Bash Bunny Primer - Hak5 2225" https://www.youtube.com/watch?v=8j6hrjSrJaM -~-~~-~~~-~~-~- Source: https://www.youtube.com/watch?v=7YBuSlmv3P4 Uploader: Hak5

Practice Workbook Linux Filter Commands

There is a lot to know about Linux. If you know the basic commands of Linux then this cheat sheet can help you take your skills to the next level. In this cheat sheet, author Maxim Burgerhout, uses the development of a LAMP application as an example and provides commands to: Get started developing a web application on Red Hat Enterprise Linux 7 Set up a SELinux boolean Run a program in the background in your shell Use Java instead of PHP Try it out on Red Hat Enterprise Linux 7 here.

This week we are checking out more expansion commands with nesting and parameters. Source: https://www.youtube.com/watch?v=cQHua6LPLyc Uploader: Hak5

20 Basic Linux Commands

20 Basic Linux Commands

some basic commands for fedora and redhat based operating systems

The Linux Commands Handbook follows the 80/20 rule: learn in 20% of the time the 80% of a topic. I find this approach gives a well-rounded overview. This book does not try to cover everything under the sun related to Linux and its commands. It focuses on the small core commands that you will use the 80% or 90% of the time, trying to simplify the usage of the more complex ones. All those commands work on Linux, macOS, WSL, and anywhere you have a UNIX environment. I hope the contents of this book will help you achieve what you want: get comfortable with Linux. This book is written by Flavio. I publish programming tutorials every day on my website flaviocopes.com. You can reach me on Twitter @flaviocopes. Enjoy!

This is a tutorial for basic LINUX Commands using the command line. Uploaded into the Public Domain under the Creative Commons License by Gerard Arthus.

Part two! Learn many networking commands you need to know to get started in Linux! ------------------------------- Shop: http://www.hakshop.com Support: http://www.patreon.com/threatwire Subscribe: http://www.youtube.com/hak5 Our Site: http://www.hak5.org Contact Us: http://www.twitter.com/hak5 Threat Wire RSS: https://shannonmorse.podbean.com/feed/ Threat Wire iTunes: https://itunes.apple.com/us/podcast/threat-wire/id1197048999 Help us with Translations! http://www.youtube.com/timedtext_cs_panel?tab=2&c=UC3s0BtrBJpwNDaflRSoiieQ ------------------------------ https://www.hak5.org/episodes/haktip-9 https://www.youtube.com/watch?v=JLF6y85LZuw -~-~~-~~~-~~-~- Please watch: "Bash Bunny Primer - Hak5 2225" https://www.youtube.com/watch?v=8j6hrjSrJaM -~-~~-~~~-~~-~- Source: https://www.youtube.com/watch?v=RrmWU_Hg9e4 Uploader: Hak5

Practice Workbook Linux Filter Commands

belowelu sanogu rizuli fiporewed vakurar

Hello Everyone, Today's Learning Linux Series, gives you the opportunity, to see you useful commands for Kali Linux. The commands that we will be looking at today are : pwd command: print working directory ls command: List information about files cd command: Change Directory echo command: Display message on screen mkdir command: Create new folders cp command: Copy one or more files to another location rm command: Remove files rmdir command: Remove folders rm command: Remove files We hope you enjoy the Tutorial. Disclaimer : This Video is for Educational Purpose Only, what you do is your responsibility and Black Hat Ethical Hacking or anyone involved, is not held accounted for if any damage for any reason occurs. Sound Track: ROYALTY FREE Slow - Trap Rap Beat x Instrumental (Prod. Alex soto beats) Background Music For Videos Fashion Films - Dark Hip-Hop Trap [Royalty Free - Commercial Use] Download for Free our Conky Theme https://github.com/blackhatethicalhacking/howtoscanatargetblackhatstyle -------------------------- Follow us Online: Facebook: https://www.facebook.com/secur1ty1samyth Twitter: https://twitter.com/secur1ty1samyth Instagram: https://www.instagram.com/blackhatethicalhacking Linked In: https://www.linkedin.com/company/black-hat-ethical-hacking Github: https://github.com/blackhatethicalhacking Support our work on Patreon: https://www.patreon.com/blackhatethicalhacking -------------------------- Source: https://www.youtube.com/watch?v=60li7X-bnkE Uploader: Black Hat Ethical Hacking

The all Kali linux Commands are inside So learn and execute love you peace all :-)