_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)_
<tdclass="tg-yw4l">Perform a CRC checksum for files.</td>
</tr>
<tr>
<tdclass="tg-yw4l">clear</td>
<tdclass="tg-yw4l">Used to clear the terminal window.</td>
</tr>
<tr>
<tdclass="tg-yw4l">cmp</td>
<tdclass="tg-yw4l">Compare two files (byte by byte).</td>
</tr>
<tr>
<tdclass="tg-yw4l">col</td>
<tdclass="tg-yw4l">Filter reverse (and half-reverse) line feeds from the input.</td>
</tr>
<tr>
<tdclass="tg-yw4l">colcrt</td>
<tdclass="tg-yw4l">Filter nroff output for CRT previewing.</td>
</tr>
<tr>
<tdclass="tg-yw4l">colrm</td>
<tdclass="tg-yw4l">Remove columns from the lines of a file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">column</td>
<tdclass="tg-yw4l">A utility that formats its input into columns.</td>
</tr>
<tr>
<tdclass="tg-yw4l">comm</td>
<tdclass="tg-yw4l">Used to compare two sorted files line by line.</td>
</tr>
<tr>
<tdclass="tg-yw4l">command</td>
<tdclass="tg-yw4l">Used to execute a command with arguments ignoring shell function named command.</td>
</tr>
<tr>
<tdclass="tg-yw4l">compress</td>
<tdclass="tg-yw4l">Used to compress one or more file(s) and replacing the originals ones.</td>
</tr>
<tr>
<tdclass="tg-yw4l">continue</td>
<tdclass="tg-yw4l">Resume the next iteration of a loop.</td>
</tr>
<tr>
<tdclass="tg-yw4l">cp</td>
<tdclass="tg-yw4l">Copy contents of one file to another.</td>
</tr>
<tr>
<tdclass="tg-yw4l">cpio</td>
<tdclass="tg-yw4l">Copy files from and to archives.</td>
</tr>
<tr>
<tdclass="tg-yw4l">cpp</td>
<tdclass="tg-yw4l">GNU C language processor.</td>
</tr>
<tr>
<tdclass="tg-yw4l">cron</td>
<tdclass="tg-yw4l">A daemon to execute scheduled commands.</td>
</tr>
<tr>
<tdclass="tg-yw4l">crond</td>
<tdclass="tg-yw4l">Same work as cron.</td>
</tr>
<tr>
<tdclass="tg-yw4l">crontab</td>
<tdclass="tg-yw4l">Manage crontab files (containing schedules commands) for users.</td>
</tr>
<tr>
<tdclass="tg-yw4l">csplit</td>
<tdclass="tg-yw4l">Split a file into sections on the basis of context lines.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ctags</td>
<tdclass="tg-yw4l">Make a list of functions and macro names defined in a programming source file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">cupsd</td>
<tdclass="tg-yw4l">A scheduler for CUPS.</td>
</tr>
<tr>
<tdclass="tg-yw4l">curl</td>
<tdclass="tg-yw4l">Used to transfer data from or to a server using supported protocols.</td>
</tr>
<tr>
<tdclass="tg-yw4l">cut</td>
<tdclass="tg-yw4l">Used to remove sections from each line of a file(s).</td>
</tr>
<tr>
<tdclass="tg-yw4l">cvs</td>
<tdclass="tg-yw4l">Concurrent Versions System. Used to track file versions, allow storage/retrieval of previous versions, and enables multiple users to work on the same file.</td>
</tr>
</tbody>
</table>
[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table)
<h2> D</h2>
<tableclass="tg">
<tbody>
<tr>
<thclass="tg-yw4l">Command</th>
<thclass="tg-yw4l">Description</th>
</tr>
<tr>
<tdclass="tg-yw4l">date</td>
<tdclass="tg-yw4l">Show system date and time.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dc</td>
<tdclass="tg-yw4l">Desk calculator utility.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dd</td>
<tdclass="tg-yw4l">Used to convert and copy a file, create disk clone, write disk headers, etc.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ddrescue</td>
<tdclass="tg-yw4l">Used to recover data from a crashed partition.</td>
</tr>
<tr>
<tdclass="tg-yw4l">deallocvt</td>
<tdclass="tg-yw4l">Deallocates kernel memory for unused virtual consoles.</td>
</tr>
<tr>
<tdclass="tg-yw4l">debugfs</td>
<tdclass="tg-yw4l">File system debugger for ext2/ext3/ext4</td>
</tr>
<tr>
<tdclass="tg-yw4l">declare</td>
<tdclass="tg-yw4l">Used to declare variables and assign attributes.</td>
</tr>
<tr>
<tdclass="tg-yw4l">depmod</td>
<tdclass="tg-yw4l">Generate modules.dep and map files.</td>
</tr>
<tr>
<tdclass="tg-yw4l">devdump</td>
<tdclass="tg-yw4l">Interactively displays the contents of device or file system ISO.</td>
</tr>
<tr>
<tdclass="tg-yw4l">df</td>
<tdclass="tg-yw4l">Show disk usage.</td>
</tr>
<tr>
<tdclass="tg-yw4l">diff</td>
<tdclass="tg-yw4l">Used to compare files line by line.</td>
</tr>
<tr>
<tdclass="tg-yw4l">diff3</td>
<tdclass="tg-yw4l">Compare three files line by line.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dig</td>
<tdclass="tg-yw4l">Domain Information Groper, a DNS lookup utility.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dir</td>
<tdclass="tg-yw4l">List the contents of a directory.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dircolors</td>
<tdclass="tg-yw4l">Set colors for ‘ls’ by altering the LS_COLORS environment variable.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dirname</td>
<tdclass="tg-yw4l">Display pathname after removing the last slash and characters thereafter.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dirs</td>
<tdclass="tg-yw4l">Show the list of remembered directories.</td>
</tr>
<tr>
<tdclass="tg-yw4l">disable</td>
<tdclass="tg-yw4l">Restrict access to a printer.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dlpsh</td>
<tdclass="tg-yw4l">Interactive Desktop Link Protocol (DLP) shell for PalmOS.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dmesg</td>
<tdclass="tg-yw4l">Examine and control the kernel ring buffer.</td>
<tdclass="tg-yw4l">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.</td>
<tdclass="tg-yw4l">Show information about the keyboard driver’s current translation tables.</td>
</tr>
</tbody>
</table>
[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table)
<h2> E</h2>
<tableclass="tg">
<tbody>
<tr>
<thclass="tg-yw4l">Command</th>
<thclass="tg-yw4l">Description</th>
</tr>
<tr>
<tdclass="tg-yw4l">e2fsck</td>
<tdclass="tg-yw4l">Used to check ext2/ext3/ext4 file systems.</td>
</tr>
<tr>
<tdclass="tg-yw4l">e2image</td>
<tdclass="tg-yw4l">Store important ext2/ext3/ext4 filesystem metadata to a file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">e2label</td>
<tdclass="tg-yw4l">Show or change the label on an ext2/ext3/ext4 filesystem.</td>
</tr>
<tr>
<tdclass="tg-yw4l">echo</td>
<tdclass="tg-yw4l">Send input string(s) to standard output i.e. display text on the screen.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ed</td>
<tdclass="tg-yw4l">GNU Ed – a line-oriented text editor.</td>
</tr>
<tr>
<tdclass="tg-yw4l">edquota</td>
<tdclass="tg-yw4l">Used to edit filesystem quotas using a text editor, such as vi.</td>
</tr>
<tr>
<tdclass="tg-yw4l">egrep</td>
<tdclass="tg-yw4l">Search and display text matching a pattern.</td>
</tr>
<tr>
<tdclass="tg-yw4l">eject</td>
<tdclass="tg-yw4l">Eject removable media.</td>
</tr>
<tr>
<tdclass="tg-yw4l">elvtune</td>
<tdclass="tg-yw4l">Used to set latency in the elevator algorithm used to schedule I/O activities for specified block devices.</td>
</tr>
<tr>
<tdclass="tg-yw4l">emacs</td>
<tdclass="tg-yw4l">Emacs text editor command line utility.</td>
</tr>
<tr>
<tdclass="tg-yw4l">enable</td>
<tdclass="tg-yw4l">Used to enable/disable shell builtin commands.</td>
</tr>
<tr>
<tdclass="tg-yw4l">env</td>
<tdclass="tg-yw4l">Run a command in a modified environment. Show/set/delete environment variables.</td>
</tr>
<tr>
<tdclass="tg-yw4l">envsubst</td>
<tdclass="tg-yw4l">Substitute environment variable values in shell format strings.</td>
</tr>
<tr>
<tdclass="tg-yw4l">esd</td>
<tdclass="tg-yw4l">Start the Enlightenment Sound Daemon (EsounD or esd). Enables multiple applications to access the same audio device simultaneously.</td>
<tdclass="tg-yw4l">Use EsounD to send audio data from a specified file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">esdctl</td>
<tdclass="tg-yw4l">EsounD control program.</td>
</tr>
<tr>
<tdclass="tg-yw4l">esddsp</td>
<tdclass="tg-yw4l">Used to reroute non-esd audio data to esd and control all the audio using esd.</td>
</tr>
<tr>
<tdclass="tg-yw4l">esdmon</td>
<tdclass="tg-yw4l">Used to copy the sound being sent to a device. Also, send it to a secondary device.</td>
</tr>
<tr>
<tdclass="tg-yw4l">esdplay</td>
<tdclass="tg-yw4l">Use EsounD system to play a file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">esdrec</td>
<tdclass="tg-yw4l">Use EsounD to record audio to a specified file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">esdsample</td>
<tdclass="tg-yw4l">Sample audio using esd.</td>
</tr>
<tr>
<tdclass="tg-yw4l">etags</td>
<tdclass="tg-yw4l">Used to create a list of functions and macros from a programming source file. These etags are used by emacs. For vi, use ctags.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ethtool</td>
<tdclass="tg-yw4l">Used to query and control network driver and hardware settings.</td>
</tr>
<tr>
<tdclass="tg-yw4l">eval</td>
<tdclass="tg-yw4l">Used to evaluate multiple commands or arguments are once.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ex</td>
<tdclass="tg-yw4l">Interactive command</td>
</tr>
<tr>
<tdclass="tg-yw4l">exec</td>
<tdclass="tg-yw4l">An interactive line-based text editor.</td>
</tr>
<tr>
<tdclass="tg-yw4l">exit</td>
<tdclass="tg-yw4l">Exit from the terminal.</td>
</tr>
<tr>
<tdclass="tg-yw4l">expand</td>
<tdclass="tg-yw4l">Convert tabs into spaces in a given file and show the output.</td>
</tr>
<tr>
<tdclass="tg-yw4l">expect</td>
<tdclass="tg-yw4l">An extension to the Tcl script, it’s used to automate interaction with other applications based on their expected output.</td>
</tr>
<tr>
<tdclass="tg-yw4l">export</td>
<tdclass="tg-yw4l">Used to set an environment variable.</td>
</tr>
<tr>
<tdclass="tg-yw4l">expr</td>
<tdclass="tg-yw4l">Evaluate expressions and display them on standard output.</td>
</tr>
</tbody>
</table>
[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table)
<h2> F</h2>
<tableclass="tg">
<tbody>
<tr>
<thclass="tg-yw4l">Command</th>
<thclass="tg-yw4l">Description</th>
</tr>
<tr>
<tdclass="tg-yw4l">factor</td>
<tdclass="tg-yw4l">Display prime factors of specified integer numbers.</td>
</tr>
<tr>
<tdclass="tg-yw4l">false</td>
<tdclass="tg-yw4l">Do nothing, unsuccessfully. Exit with a status code indicating failure.</td>
<tdclass="tg-yw4l">Display contents of an MS-DOS file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">mv</td>
<tdclass="tg-yw4l">Move/rename files or directories.</td>
</tr>
<tr>
<tdclass="tg-yw4l">mzip</td>
<tdclass="tg-yw4l">Change protection mode and eject disk on Zip/Jaz drive.</td>
</tr>
</tbody>
</table>
[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table)
<h2> N</h2>
<tableclass="tg">
<tbody>
<tr>
<thclass="tg-yw4l">Command</th>
<thclass="tg-yw4l">Description</th>
</tr>
<tr>
<tdclass="tg-yw4l">named</td>
<tdclass="tg-yw4l">Internet domain name server.</td>
</tr>
<tr>
<tdclass="tg-yw4l">namei</td>
<tdclass="tg-yw4l">Follow a pathname until a terminal point is found.</td>
</tr>
<tr>
<tdclass="tg-yw4l">nameif</td>
<tdclass="tg-yw4l">Name network interfaces based on MAC addresses.</td>
</tr>
<tr>
<tdclass="tg-yw4l">nc</td>
<tdclass="tg-yw4l">Netcat utility. Arbitrary TCP and UDP connections and listens.</td>
</tr>
<tr>
<tdclass="tg-yw4l">netstat</td>
<tdclass="tg-yw4l">Show network information.</td>
</tr>
<tr>
<tdclass="tg-yw4l">newaliases</td>
<tdclass="tg-yw4l">Rebuilds mail alias database.</td>
</tr>
<tr>
<tdclass="tg-yw4l">newgrp</td>
<tdclass="tg-yw4l">Log-in to a new group.</td>
</tr>
<tr>
<tdclass="tg-yw4l">newusers</td>
<tdclass="tg-yw4l">Update/create new users in batch.</td>
</tr>
<tr>
<tdclass="tg-yw4l">nfsd</td>
<tdclass="tg-yw4l">Special filesystem for controlling Linux NFS server.</td>
</tr>
<tr>
<tdclass="tg-yw4l">nfsstat</td>
<tdclass="tg-yw4l">List NFS statistics.</td>
</tr>
<tr>
<tdclass="tg-yw4l">nice</td>
<tdclass="tg-yw4l">Run a program with modified scheduling priority.</td>
</tr>
<tr>
<tdclass="tg-yw4l">nl</td>
<tdclass="tg-yw4l">Show numbered line while displaying the contents of a file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">nm</td>
<tdclass="tg-yw4l">List symbols from object files.</td>
</tr>
<tr>
<tdclass="tg-yw4l">nohup</td>
<tdclass="tg-yw4l">Run a command immune to hangups.</td>
</tr>
<tr>
<tdclass="tg-yw4l">notify-send</td>
<tdclass="tg-yw4l">A program to send desktop notifications.</td>
</tr>
<tr>
<tdclass="tg-yw4l">nslookup</td>
<tdclass="tg-yw4l">Used performs DNS queries. Read this article for more info.</td>
</tr>
<tr>
<tdclass="tg-yw4l">nsupdate</td>
<tdclass="tg-yw4l">Dynamic DNS update utility.</td>
</tr>
</tbody>
</table>
[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table)
<h2> O</h2>
<tableclass="tg">
<tbody>
<tr>
<thclass="tg-yw4l">Command</th>
<thclass="tg-yw4l">Description</th>
</tr>
<tr>
<tdclass="tg-yw4l">objcopy</td>
<tdclass="tg-yw4l">Copy and translate object files.</td>
</tr>
<tr>
<tdclass="tg-yw4l">objdump</td>
<tdclass="tg-yw4l">Display information from object files.</td>
</tr>
<tr>
<tdclass="tg-yw4l">od</td>
<tdclass="tg-yw4l">Dump files in octal and other formats.</td>
</tr>
<tr>
<tdclass="tg-yw4l">op</td>
<tdclass="tg-yw4l">Operator access, allows system administrators to grant users access to certain root operations that require superuser privileges.</td>
</tr>
<tr>
<tdclass="tg-yw4l">open</td>
<tdclass="tg-yw4l">Open a file using its default application.</td>
</tr>
<tr>
<tdclass="tg-yw4l">openvt</td>
<tdclass="tg-yw4l">Start a program on a new virtual terminal (VT).</td>
</tr>
</tbody>
</table>
[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table)
<h2> P</h2>
<tableclass="tg">
<tbody>
<tr>
<thclass="tg-yw4l">Command</th>
<thclass="tg-yw4l">Description</th>
</tr>
<tr>
<tdclass="tg-yw4l">passwd</td>
<tdclass="tg-yw4l">Change user password.</td>
</tr>
<tr>
<tdclass="tg-yw4l">paste</td>
<tdclass="tg-yw4l">Merge lines of files. Write to standard output, TAB-separated lines consisting of sequentially corresponding lines from each file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">patch</td>
<tdclass="tg-yw4l">Apply a patchfile (containing differences listing by diff program) to an original file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">pathchk</td>
<tdclass="tg-yw4l">Check if file names are valid or portable.</td>
</tr>
<tr>
<tdclass="tg-yw4l">perl</td>
<tdclass="tg-yw4l">Perl 5 language interpreter.</td>
</tr>
<tr>
<tdclass="tg-yw4l">pgrep</td>
<tdclass="tg-yw4l">List process IDs matching the specified criteria among all the running processes.</td>
</tr>
<tr>
<tdclass="tg-yw4l">pidof</td>
<tdclass="tg-yw4l">Find process ID of a running program.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ping</td>
<tdclass="tg-yw4l">Send ICMP ECHO_REQUEST to network hosts.</td>
</tr>
<tr>
<tdclass="tg-yw4l">pinky</td>
<tdclass="tg-yw4l">Lightweight finger.</td>
</tr>
<tr>
<tdclass="tg-yw4l">pkill</td>
<tdclass="tg-yw4l">Send kill signal to processes based on name and other attributes.</td>
</tr>
<tr>
<tdclass="tg-yw4l">pmap</td>
<tdclass="tg-yw4l">Report memory map of a process.</td>
</tr>
<tr>
<tdclass="tg-yw4l">popd</td>
<tdclass="tg-yw4l">Removes directory on the head of the directory stack and takes you to the new directory on the head.</td>
</tr>
<tr>
<tdclass="tg-yw4l">portmap</td>
<tdclass="tg-yw4l">Converts RPC program numbers to IP port numbers.</td>
<tdclass="tg-yw4l">Shows disk usage, and space limits for a user or group. Without arguments, only shows user quotas.</td>
</tr>
<tr>
<tdclass="tg-yw4l">quotacheck</td>
<tdclass="tg-yw4l">Used to scan a file system for disk usage.</td>
</tr>
<tr>
<tdclass="tg-yw4l">quotactl</td>
<tdclass="tg-yw4l">Make changes to disk quotas.</td>
</tr>
<tr>
<tdclass="tg-yw4l">quotaoff</td>
<tdclass="tg-yw4l">Enable enforcement of filesystem quotas.</td>
</tr>
<tr>
<tdclass="tg-yw4l">quotaon</td>
<tdclass="tg-yw4l">Disable enforcement of filesystem quotas.</td>
</tr>
<tr>
<tdclass="tg-yw4l">quotastats</td>
<tdclass="tg-yw4l">Shows the report of quota system statistics gathered from the kernel.</td>
</tr>
</tbody>
</table>
[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table)
<h2> R</h2>
<tableclass="tg">
<tbody>
<tr>
<thclass="tg-yw4l">Command</th>
<thclass="tg-yw4l">Description</th>
</tr>
<tr>
<tdclass="tg-yw4l">raidstart</td>
<tdclass="tg-yw4l">Start/stop RAID devices.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ram</td>
<tdclass="tg-yw4l">RAM disk device used to access the RAM disk in raw mode.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ramsize</td>
<tdclass="tg-yw4l">Show usage information for the RAM disk.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ranlib</td>
<tdclass="tg-yw4l">Generate index to the contents of an archive and store it in the archive.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rar</td>
<tdclass="tg-yw4l">Create and manage RAR file in Linux.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rarpd</td>
<tdclass="tg-yw4l">Respond to Reverse Address Resolution Protocol (RARP) requests.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rcp</td>
<tdclass="tg-yw4l">Remote copy command to copy files between remote computers.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rdate</td>
<tdclass="tg-yw4l">Set system date and time by fetching information from a remote machine.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rdev</td>
<tdclass="tg-yw4l">Set or query RAM disk size, image root device, or video mode.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rdist</td>
<tdclass="tg-yw4l">Remote file distribution client, maintains identical file copies over multiple hosts.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rdistd</td>
<tdclass="tg-yw4l">Start the rdist server.</td>
</tr>
<tr>
<tdclass="tg-yw4l">read</td>
<tdclass="tg-yw4l">Read from a file descriptor.</td>
</tr>
<tr>
<tdclass="tg-yw4l">readarray</td>
<tdclass="tg-yw4l">Read lines from a file into an array variable.</td>
</tr>
<tr>
<tdclass="tg-yw4l">readcd</td>
<tdclass="tg-yw4l">Read/write compact disks.</td>
</tr>
<tr>
<tdclass="tg-yw4l">readelf</td>
<tdclass="tg-yw4l">Shows information about ELF (Executable and Linkable format) files.</td>
</tr>
<tr>
<tdclass="tg-yw4l">readlink</td>
<tdclass="tg-yw4l">Display value of a symbolic link or canonical file name.</td>
</tr>
<tr>
<tdclass="tg-yw4l">readonly</td>
<tdclass="tg-yw4l">Mark functions and variables as read-only.</td>
</tr>
<tr>
<tdclass="tg-yw4l">reboot</td>
<tdclass="tg-yw4l">Restart the machine.</td>
</tr>
<tr>
<tdclass="tg-yw4l">reject</td>
<tdclass="tg-yw4l">Accept/reject print jobs sent to a specified destination.</td>
</tr>
<tr>
<tdclass="tg-yw4l">remsync</td>
<tdclass="tg-yw4l">Synchronize remote files over email.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rename</td>
<tdclass="tg-yw4l">Rename one or more files.</td>
</tr>
<tr>
<tdclass="tg-yw4l">renice</td>
<tdclass="tg-yw4l">Change priority of active processes.</td>
</tr>
<tr>
<tdclass="tg-yw4l">repquota</td>
<tdclass="tg-yw4l">Report disk usage and quotas for a specified filesystem.</td>
</tr>
<tr>
<tdclass="tg-yw4l">reset</td>
<tdclass="tg-yw4l">Reinitialize the terminal.</td>
</tr>
<tr>
<tdclass="tg-yw4l">resize2fs</td>
<tdclass="tg-yw4l">Used to resize ext2/ext3/ext4 file systems.</td>
</tr>
<tr>
<tdclass="tg-yw4l">restore</td>
<tdclass="tg-yw4l">Restore files from a backup created using dump.</td>
</tr>
<tr>
<tdclass="tg-yw4l">return</td>
<tdclass="tg-yw4l">Exit a shell function.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rev</td>
<tdclass="tg-yw4l">Show contents of a file, reversing the order of characters in every line.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rexec</td>
<tdclass="tg-yw4l">Remote execution client for exec server.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rexecd</td>
<tdclass="tg-yw4l">Remote execution server.</td>
</tr>
<tr>
<tdclass="tg-yw4l">richtext</td>
<tdclass="tg-yw4l">View “richtext” on an ACSII terminal.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rlogin</td>
<tdclass="tg-yw4l">Used to connect a local host system with a remote host.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rlogind</td>
<tdclass="tg-yw4l">Acts as the server for rlogin.It facilitates remote login, and authentication based on privileged port numbers from trusted hosts.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rm</td>
<tdclass="tg-yw4l">Removes specified files and directories (not by default).</td>
</tr>
<tr>
<tdclass="tg-yw4l">rmail</td>
<tdclass="tg-yw4l">Handle remote mail received via uucp.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rmdir</td>
<tdclass="tg-yw4l">Used to remove empty directories.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rmmod</td>
<tdclass="tg-yw4l">A program to remove modules from Linux kernel.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rndc</td>
<tdclass="tg-yw4l">Name server control utility. Send command to a BIND DNS server over a TCP connection.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rootflags</td>
<tdclass="tg-yw4l">Show/set flags for the kernel image.</td>
</tr>
<tr>
<tdclass="tg-yw4l">route</td>
<tdclass="tg-yw4l">Show/change IP routing table.</td>
</tr>
<tr>
<tdclass="tg-yw4l">routed</td>
<tdclass="tg-yw4l">A daemon, invoked at boot time, to manage internet routing tables.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rpcgen</td>
<tdclass="tg-yw4l">An RPC protocol compiler. Parse a file written in the RPC language.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rpcinfo</td>
<tdclass="tg-yw4l">Shows RPC information. Makes an RPC call to an RPC server and reports the findings.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rpm</td>
<tdclass="tg-yw4l">A package manager for Linux distributions. Originally developed for RedHat Linux.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rsh</td>
<tdclass="tg-yw4l">Remote shell. Connects to a specified host and executes commands.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rshd</td>
<tdclass="tg-yw4l">A daemon that acts as a server for rsh and rcp commands.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rsync</td>
<tdclass="tg-yw4l">A versitile to for copying files remotely and locally.</td>
</tr>
<tr>
<tdclass="tg-yw4l">runlevel</td>
<tdclass="tg-yw4l">Shows previous and current SysV runlevel.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rup</td>
<tdclass="tg-yw4l">Remote status display. Shows current system status for all or specified hosts on the local network.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ruptime</td>
<tdclass="tg-yw4l">Shows uptime and login details of the machines on the local network.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rusers</td>
<tdclass="tg-yw4l">Shows the list of the users logged-in to the host or on all machines on the local network.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rusersd</td>
<tdclass="tg-yw4l">The rsuerd daemon acts as a server that responds to the queries from rsuers command.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rwall</td>
<tdclass="tg-yw4l">Sends messages to all users on the local network.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rwho</td>
<tdclass="tg-yw4l">Reports who is logged-in to the hosts on the local network.</td>
</tr>
<tr>
<tdclass="tg-yw4l">rwhod</td>
<tdclass="tg-yw4l">Acts as a server for rwho and ruptime commands.</td>
</tr>
</tbody>
</table>
[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table)
<h2> S</h2>
<tableclass="tg">
<tbody>
<tr>
<thclass="tg-yw4l">Command</th>
<thclass="tg-yw4l">Description</th>
</tr>
<tr>
<tdclass="tg-yw4l">sane-find-scanner</td>
<tdclass="tg-yw4l">Find SCSI and USB scanner and determine their device files.</td>
<tdclass="tg-yw4l">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.</td>
</tr>
<tr>
<tdclass="tg-yw4l">sensors</td>
<tdclass="tg-yw4l">Shows the current readings of all sensor chips.</td>
</tr>
<tr>
<tdclass="tg-yw4l">seq</td>
<tdclass="tg-yw4l">Displays an incremental sequence of numbers from first to last.</td>
</tr>
<tr>
<tdclass="tg-yw4l">set</td>
<tdclass="tg-yw4l">Used to manipulate shell variables and functions.</td>
</tr>
<tr>
<tdclass="tg-yw4l">setfdprm</td>
<tdclass="tg-yw4l">Sets floppy disk parameters as provided by the user.</td>
<tdclass="tg-yw4l">Examines codes sent by the keyboard displays them in printable form.</td>
</tr>
<tr>
<tdclass="tg-yw4l">showmount</td>
<tdclass="tg-yw4l">Shows information about NFS server mount on the host.</td>
</tr>
<tr>
<tdclass="tg-yw4l">shred</td>
<tdclass="tg-yw4l">Overwrite a file to hide its content (optionally delete it), making it harder to recover it.</td>
</tr>
<tr>
<tdclass="tg-yw4l">shutdown</td>
<tdclass="tg-yw4l">Power-off the machine.</td>
</tr>
<tr>
<tdclass="tg-yw4l">size</td>
<tdclass="tg-yw4l">Lists section size and the total size of a specified file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">skill</td>
<tdclass="tg-yw4l">Send a signal to processes.</td>
</tr>
<tr>
<tdclass="tg-yw4l">slabtop</td>
<tdclass="tg-yw4l">Show kernel slab cache information in real-time.</td>
</tr>
<tr>
<tdclass="tg-yw4l">slattach</td>
<tdclass="tg-yw4l">Attack a network interface to a serial line.</td>
</tr>
<tr>
<tdclass="tg-yw4l">sleep</td>
<tdclass="tg-yw4l">Suspend execution for a specified amount of time (in seconds).</td>
</tr>
<tr>
<tdclass="tg-yw4l">slocate</td>
<tdclass="tg-yw4l">Display matches by searching filename databases. Takes ownership and file permission into consideration.</td>
</tr>
<tr>
<tdclass="tg-yw4l">snice</td>
<tdclass="tg-yw4l">Reset priority for processes.</td>
</tr>
<tr>
<tdclass="tg-yw4l">sort</td>
<tdclass="tg-yw4l">Sort lines of text files.</td>
</tr>
<tr>
<tdclass="tg-yw4l">source</td>
<tdclass="tg-yw4l">Run commands from a specified file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">split</td>
<tdclass="tg-yw4l">Split a file into pieces of fixed size.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ss</td>
<tdclass="tg-yw4l">Display socket statistics, similar to netstat.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ssh</td>
<tdclass="tg-yw4l">An SSH client for logging in to a remote machine. It provides encrypted communication between the hosts.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ssh-add</td>
<tdclass="tg-yw4l">Adds private key identities to the authentication agent.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ssh-agent</td>
<tdclass="tg-yw4l">It holds private keys used for public key authentication.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ssh-keygen</td>
<tdclass="tg-yw4l">It generates, manages, converts authentication keys for ssh.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ssh-keyscan</td>
<tdclass="tg-yw4l">Gather ssh public keys.</td>
</tr>
<tr>
<tdclass="tg-yw4l">sshd</td>
<tdclass="tg-yw4l">Server for the ssh program.</td>
</tr>
<tr>
<tdclass="tg-yw4l">stat</td>
<tdclass="tg-yw4l">Display file or filesystem status.</td>
</tr>
<tr>
<tdclass="tg-yw4l">statd</td>
<tdclass="tg-yw4l">A daemon that listens for reboot notifications from other hosts, and manages the list of hosts to be notified when the local system reboots.</td>
</tr>
<tr>
<tdclass="tg-yw4l">strace</td>
<tdclass="tg-yw4l">Trace system calls and signals.</td>
</tr>
<tr>
<tdclass="tg-yw4l">strfile</td>
<tdclass="tg-yw4l">Create a random access file for storing strings.</td>
</tr>
<tr>
<tdclass="tg-yw4l">strings</td>
<tdclass="tg-yw4l">Search a specified file and prints any printable strings with at least four characters and followed by an unprintable character.</td>
</tr>
<tr>
<tdclass="tg-yw4l">strip</td>
<tdclass="tg-yw4l">Discard symbols from object files.</td>
</tr>
<tr>
<tdclass="tg-yw4l">stty</td>
<tdclass="tg-yw4l">Change and print terminal line settings.</td>
</tr>
<tr>
<tdclass="tg-yw4l">su</td>
<tdclass="tg-yw4l">Change user ID or become superuser.</td>
</tr>
<tr>
<tdclass="tg-yw4l">sudo</td>
<tdclass="tg-yw4l">Execute a command as superuser.</td>
</tr>
<tr>
<tdclass="tg-yw4l">sum</td>
<tdclass="tg-yw4l">Checksum and count the block in a file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">suspend</td>
<tdclass="tg-yw4l">Suspend the execution of the current shell.</td>
</tr>
<tr>
<tdclass="tg-yw4l">swapoff</td>
<tdclass="tg-yw4l">Disable devices for paging and swapping.</td>
</tr>
<tr>
<tdclass="tg-yw4l">swapon</td>
<tdclass="tg-yw4l">Enable devices for paging and swapping.</td>
</tr>
<tr>
<tdclass="tg-yw4l">symlink</td>
<tdclass="tg-yw4l">Create a symbolic link to a file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">sync</td>
<tdclass="tg-yw4l">Synchronize cached writes to persistent storage.</td>
</tr>
<tr>
<tdclass="tg-yw4l">sysctl</td>
<tdclass="tg-yw4l">Configure kernel parameters at runtime.</td>
</tr>
<tr>
<tdclass="tg-yw4l">sysklogd</td>
<tdclass="tg-yw4l">Linux system logging utilities. Provides syslogd and klogd functionalities.</td>
</tr>
<tr>
<tdclass="tg-yw4l">syslogd</td>
<tdclass="tg-yw4l">Read and log system messages to the system console and log files.</td>
</tr>
</tbody>
</table>
[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table)
<h2> T</h2>
<tableclass="tg">
<tbody>
<tr>
<thclass="tg-yw4l">Command</th>
<thclass="tg-yw4l">Description</th>
</tr>
<tr>
<tdclass="tg-yw4l">tac</td>
<tdclass="tg-yw4l">Concatenate and print files in reverse order. Opposite of cat command.</td>
</tr>
<tr>
<tdclass="tg-yw4l">tail</td>
<tdclass="tg-yw4l">Show the last 10 lines of each specified file(s).</td>
</tr>
<tr>
<tdclass="tg-yw4l">tailf</td>
<tdclass="tg-yw4l">Follow the growth of a log file. (Deprecated command)</td>
</tr>
<tr>
<tdclass="tg-yw4l">talk</td>
<tdclass="tg-yw4l">A two-way screen-oriented communication utility that allows two user to exchange messages simultaneously.</td>
</tr>
<tr>
<tdclass="tg-yw4l">talkd</td>
<tdclass="tg-yw4l">A remote user communication server for <em>talk</em>.</td>
</tr>
<tr>
<tdclass="tg-yw4l">tar</td>
<tdclass="tg-yw4l">GNU version of the tar archiving utility. Used to store and extract multiple files from a single archive.</td>
</tr>
<tr>
<tdclass="tg-yw4l">taskset</td>
<tdclass="tg-yw4l">Set/retrieve a process’s CPU affinity.</td>
</tr>
<tr>
<tdclass="tg-yw4l">tcpd</td>
<tdclass="tg-yw4l">Access control utility for internet services.</td>
</tr>
<tr>
<tdclass="tg-yw4l">tcpdump</td>
<tdclass="tg-yw4l">Dump traffic on network. Displays a description of the contents of packets on a network interface that match the boolean expression.</td>
</tr>
<tr>
<tdclass="tg-yw4l">tcpslice</td>
<tdclass="tg-yw4l">Extract pieces of tcpdump files or merge them.</td>
</tr>
<tr>
<tdclass="tg-yw4l">tee</td>
<tdclass="tg-yw4l">Read from standard input and write to standard output and files.</td>
</tr>
<tr>
<tdclass="tg-yw4l">telinit</td>
<tdclass="tg-yw4l">Change SysV runlevel.</td>
</tr>
<tr>
<tdclass="tg-yw4l">telnet</td>
<tdclass="tg-yw4l">Telnet protocol user interface. Used to interact with another host using telnet.</td>
</tr>
<tr>
<tdclass="tg-yw4l">telnetd</td>
<tdclass="tg-yw4l">A server for the telnet protocol.</td>
</tr>
<tr>
<tdclass="tg-yw4l">test</td>
<tdclass="tg-yw4l">Check file type and compare values.</td>
</tr>
<tr>
<tdclass="tg-yw4l">tftp</td>
<tdclass="tg-yw4l">User interface to the internet TFTP (Trivial File Transfer Protocol).</td>
</tr>
<tr>
<tdclass="tg-yw4l">tftpd</td>
<tdclass="tg-yw4l">TFTP server.</td>
</tr>
<tr>
<tdclass="tg-yw4l">time</td>
<tdclass="tg-yw4l">Run programs and summarize system resource usage.</td>
</tr>
<tr>
<tdclass="tg-yw4l">timeout</td>
<tdclass="tg-yw4l">Execute a command with a time limit.</td>
</tr>
<tr>
<tdclass="tg-yw4l">times</td>
<tdclass="tg-yw4l">Shows accumulated user and system times for the shell and it’s child processes.</td>
</tr>
<tr>
<tdclass="tg-yw4l">tload</td>
<tdclass="tg-yw4l">Shows a graph of the current system load average to the specified tty.</td>
</tr>
<tr>
<tdclass="tg-yw4l">tmpwatch</td>
<tdclass="tg-yw4l">Recursively remove files and directories which haven’t been accessed for the specified period of time.</td>
</tr>
<tr>
<tdclass="tg-yw4l">top</td>
<tdclass="tg-yw4l">Displays real-time view of processes running on the system.</td>
</tr>
<tr>
<tdclass="tg-yw4l">touch</td>
<tdclass="tg-yw4l">Change file access and modification times.</td>
<tdclass="tg-yw4l">Used by system administrators in order to monitor network parameters such as bandwidth consumption or maybe some traffic flowing in or out.</td>
> 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.
<tdclass="tg-yw4l">Filename path separator [forward slash]. Separates the components of a filename. It also represents the path to root directory.</td>
</tr>
<tr>
<tdclass="tg-yw4l">\</td>
<tdclass="tg-yw4l">Escape [backslash]. A quoting mechanism for single characters. It preserves the literal value of the next character that follows, with the exception of newline.</td>
<tdclass="tg-yw4l">Pipe. This is a method of chaining commands together. Connects the output (stdout) of command1 to the input (stdin) of command2. Each command reads the previous command’s output.</td>
</tr>
<tr>
<tdclass="tg-yw4l">|&</td>
<tdclass="tg-yw4l">This operator connects the output (stdout) and error (stderr) of command1 to the input (stdin) of command2.</td>
<tdclass="tg-yw4l">The OR operator is used to chain commands. It will execute the first command then stop if successful, if not, it will proceed pass failed commands until one is successful and stop.</tr>
<tdclass="tg-yw4l">The AND operator is used to chain commands. It will execute commands only if the first command is successful and proceed until one fails.</td>
<tdclass="tg-yw4l">Force redirection (even if the <ahref="https://www.google.com/search?q=what+is+noclobber+bash+meaning+%3F&client=firefox-b-d&sxsrf=ALiCzsYjxhOR8rNOMWPfYf5DFKIqA_f7SA%3A1667859549077&ei=XYRpY4uiBMLhxgGuwoP4Cw&ved=0ahUKEwjLxNT_jJ37AhXCsDEKHS7hAL8Q4dUDCA4&uact=5&oq=what+is+noclobber+bash+meaning+%3F&gs_lcp=Cgxnd3Mtd2l6LXNlcnAQAzIHCCMQsAMQJzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwA0oECE0YAUoECEEYAEoECEYYAFAAWABg0gFoAXABeACAAQCIAQCSAQCYAQDIAQnAAQE&sclient=gws-wiz-serp"><b>noclobber</b></a> option is set). This will forcibly overwrite an existing file.
</tr>
<tr>
<tdclass="tg-yw4l">#</td>
<tdclass="tg-yw4l">Comment [number sign]. Lines in files beginning with a # (with the exception of #!) are comments and will not be executed.</td>
<tdclass="tg-yw4l">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.</td>
<tr>
<tdclass="tg-yw4l">' '</td>
<tdclass="tg-yw4l">Single quotes protects the text inside them so that it has a literal meaning. This is a stronger form of quoting than double quotes.</td>
</tr>
</tr>
<tr>
<tdclass="tg-yw4l">" "</td>
<tdclass="tg-yw4l">Whitespace. This is a tab, newline, vertical tab, form feed, carriage return, or space. Bash uses whitespace to determine where words begin and end.</td>
</tr>
<tdclass="tg-yw4l">:</td>
<tdclass="tg-yw4l">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.</td>
</tr>
<tr>
<tdclass="tg-yw4l">!</td>
<tdclass="tg-yw4l">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.</td>
</tr>
<tr>
<tdclass="tg-yw4l">*</td>
<tdclass="tg-yw4l">Wild card [asterisk]. The * character serves as a "wild card" for filename expansion in <ahref="https://www.google.com/search?q=What+is+globbing+in+shell%3F&client=firefox-b-d&sxsrf=ALiCzsYC9z8Ynyd5KFHYK7jo2SDHxrCuxg%3A1667844117587&ei=FUhpY77DI46ykvQPlPO_8A8&ved=0ahUKEwj-oa3B05z7AhUOmYQIHZT5D_4Q4dUDCA4&uact=5&oq=What+is+globbing+in+shell%3F&gs_lcp=Cgxnd3Mtd2l6LXNlcnAQAzIICAAQFhAeEA8yBQgAEIYDMgUIABCGAzIFCAAQhgMyBQgAEIYDOgQIABBHSgQITRgBSgQIQRgASgQIRhgAUPdAWPdAYJ9DaABwA3gAgAGdAYgBnQGSAQMwLjGYAQCgAQKgAQHIAQjAAQE&sclient=gws-wiz-serp"><b>globbing</b></a>. By itself, it matches every filename in a given directory.
</td>
<tr>
<tdclass="tg-yw4l">?</td>
<tdclass="tg-yw4l">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.</td>
</tr>
<tr>
<tdclass="tg-yw4l">{ }</td>
<tdclass="tg-yw4l">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.</td>
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<tdclass="tg-yw4l">( )</td>
<tdclass="tg-yw4l"><ahref="https://www.google.com/search?q=what+is+linux+Subshell+%3F&client=firefox-b-d&biw=1440&bih=660&sxsrf=ALiCzsanH7oWuGhBf-7bIH_SmJhmw9gGxg%3A1667750422612&ei=FtpnY5KDJdeCwbkP3eejiAc&ved=0ahUKEwiS5o289pn7AhVXQTABHd3zCHEQ4dUDCA4&uact=5&oq=what+is+linux+Subshell+%3F&gs_lcp=Cgxnd3Mtd2l6LXNlcnAQAzIECCMQJzoKCAAQRxDWBBCwA0oECE0YAUoECEEYAEoECEYYAFCyBliyBmC7B2gCcAF4AIABcYgBcZIBAzAuMZgBAKABAcgBCMABAQ&sclient=gws-wiz-serp"><b>Subshell</b></a> 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.</td>
