_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>
</tr>
<tr>
<tdclass="tg-yw4l">dnsdomainname</td>
<tdclass="tg-yw4l">Show the DNS domain name of the system.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dnssec-keygen</td>
<tdclass="tg-yw4l">Generate encrypted Secure DNS keys for a given domain name.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dnssec-makekeyset</td>
<tdclass="tg-yw4l">Produce domain key set from one or more DNS security keys generated by dnssec-keygen.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dnssec-signkey</td>
<tdclass="tg-yw4l">Sign a secure DNS keyset with key signatures specified in the list of key-identifiers.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dnssec-signzone</td>
<tdclass="tg-yw4l">Sign a secure DNS zonefile with the signatures in the specified list of key-identifiers.</td>
</tr>
<tr>
<tdclass="tg-yw4l">doexec</td>
<tdclass="tg-yw4l">Used to run an executable with an arbitrary argv list provided.</td>
</tr>
<tr>
<tdclass="tg-yw4l">domainname</td>
<tdclass="tg-yw4l">Show or set the name of current NIS (Network Information Services) domain.</td>
</tr>
<tr>
<tdclass="tg-yw4l">dosfsck</td>
<tdclass="tg-yw4l">Check and repair MS-DOS file systems.</td>
</tr>
<tr>
<tdclass="tg-yw4l">du</td>
<tdclass="tg-yw4l">Show disk usage summary for a file(s).</td>
</tr>
<tr>
<tdclass="tg-yw4l">dump</td>
<tdclass="tg-yw4l">Backup utility for ext2/ext3 file systems.</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>
</tr>
<tr>
<tdclass="tg-yw4l">fc-cache</td>
<tdclass="tg-yw4l">Make font information cache after scanning the directories.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fc-list</td>
<tdclass="tg-yw4l">Show the list of available fonts.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fdformat</td>
<tdclass="tg-yw4l">Do a low-level format on a floppy disk.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fdisk</td>
<tdclass="tg-yw4l">Make changes to the disk partition table.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fetchmail</td>
<tdclass="tg-yw4l">Fetch mail from mail servers and forward it to the local mail delivery system.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fg</td>
<tdclass="tg-yw4l">Used to send a job to the foreground.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fgconsole</td>
<tdclass="tg-yw4l">Display the number of the current virtual console.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fgrep</td>
<tdclass="tg-yw4l">Display lines from a file(s) that match a specified string. A variant of grep.</td>
</tr>
<tr>
<tdclass="tg-yw4l">file</td>
<tdclass="tg-yw4l">Determine file type for a file.</td>
</tr>
<tr>
<tdclass="tg-yw4l">find</td>
<tdclass="tg-yw4l">Do a file search in a directory hierarchy.</td>
</tr>
<tr>
<tdclass="tg-yw4l">finger</td>
<tdclass="tg-yw4l">Display user data including the information listed in <em>.plan</em>and <em>.project</em>in each user’s home directory.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fingerd</td>
<tdclass="tg-yw4l">Provides a network interface for the finger program.</td>
</tr>
<tr>
<tdclass="tg-yw4l">flex</td>
<tdclass="tg-yw4l">Generate programs that perform pattern-matching on text.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fmt</td>
<tdclass="tg-yw4l">Used to convert text to a specified width by filling lines and removing new lines, displaying the output.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fold</td>
<tdclass="tg-yw4l">Wrap input line to fit in a specified width.</td>
</tr>
<tr>
<tdclass="tg-yw4l">for</td>
<tdclass="tg-yw4l">Expand words and run commands for each one in the resultant list.</td>
</tr>
<tr>
<tdclass="tg-yw4l">formail</td>
<tdclass="tg-yw4l">Used to filter standard input into mailbox format.</td>
</tr>
<tr>
<tdclass="tg-yw4l">format</td>
<tdclass="tg-yw4l">Used to format disks.</td>
</tr>
<tr>
<tdclass="tg-yw4l">free</td>
<tdclass="tg-yw4l">Show free and used system memory.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fsck</td>
<tdclass="tg-yw4l">Check and repair a Linux file system</td>
</tr>
<tr>
<tdclass="tg-yw4l">ftp</td>
<tdclass="tg-yw4l">File transfer protocol user interface.</td>
</tr>
<tr>
<tdclass="tg-yw4l">ftpd</td>
<tdclass="tg-yw4l">FTP server process.</td>
</tr>
<tr>
<tdclass="tg-yw4l">function</td>
<tdclass="tg-yw4l">Used to define function macros.</td>
</tr>
<tr>
<tdclass="tg-yw4l">fuser</td>
<tdclass="tg-yw4l">Find and kill a process accessing a file.</td>
</tr>
</tbody>
</table>
[⬆ ʀᴇᴛᴜʀɴ ᴛᴏ ᴛᴏᴩ](#table)
<h2> G</h2>
<tableclass="tg">
<tbody>
<tr>
<thclass="tg-yw4l">Command</th>
<thclass="tg-yw4l">Description</th>
</tr>
<tr>
<tdclass="tg-yw4l">g++</td>
<tdclass="tg-yw4l">Run the g++ compiler.</td>
</tr>
<tr>
<tdclass="tg-yw4l">gawk</td>
<tdclass="tg-yw4l">Used for pattern scanning and language processing. A GNU implementation of AWK language.</td>
</tr>
<tr>
<tdclass="tg-yw4l">gcc</td>
<tdclass="tg-yw4l">A C and C++ compiler by GNU.</td>
</tr>
<tr>
<tdclass="tg-yw4l">gdb</td>
<tdclass="tg-yw4l">A utility to debug programs and know about where it crashes.</td>
</tr>
<tr>
<tdclass="tg-yw4l">getent</td>
<tdclass="tg-yw4l">Shows entries from Name Service Switch Libraries for specified keys.</td>
</tr>
<tr>
<tdclass="tg-yw4l">getkeycodes</td>
<tdclass="tg-yw4l">Displays the kernel scancode-to-keycode mapping table.</td>
</tr>
<tr>
<tdclass="tg-yw4l">getopts</td>
<tdclass="tg-yw4l">A utility to parse positional parameters.</td>
</tr>
<tr>
<tdclass="tg-yw4l">gpasswd</td>
<tdclass="tg-yw4l">Allows an administrator to change group passwords.</td>
</tr>
<tr>
<tdclass="tg-yw4l">gpg</td>
<tdclass="tg-yw4l">Enables encryption and signing services as per the OpenPGP standard.</td>
</tr>
<tr>
<tdclass="tg-yw4l">gpgsplit</td>
<tdclass="tg-yw4l">Used to split an OpenPGP message into packets.</td>
</tr>
<tr>
<tdclass="tg-yw4l">gpgv</td>
<tdclass="tg-yw4l">Used to verify OpenPGP signatures.</td>
</tr>
<tr>
<tdclass="tg-yw4l">gpm</td>
<tdclass="tg-yw4l">It enables cut and paste functionality and a mouse server for the Linux console.</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>
</tr>
<tr>
<tdclass="tg-yw4l">scanadf</td>
<tdclass="tg-yw4l">Retrieve multiple images from a scanner equipped with an automatic document feeder (ADF).</td>
</tr>
<tr>
<tdclass="tg-yw4l">scanimage</td>
<tdclass="tg-yw4l">Read images from image acquisition devices (scanner or camera) and display on standard output in PNM (Portable aNyMap) format.</td>
</tr>
<tr>
<tdclass="tg-yw4l">scp</td>
<tdclass="tg-yw4l">Copy files between hosts on a network securely using SSH.</td>
</tr>
<tr>
<tdclass="tg-yw4l">screen</td>
<tdclass="tg-yw4l">A window manager that enables multiple pseudo-terminals with the help of ANSI/VT100 terminal emulation.</td>
</tr>
<tr>
<tdclass="tg-yw4l">script</td>
<tdclass="tg-yw4l">Used to make a typescript of everything displayed on the screen during a terminal session.</td>
</tr>
<tr>
<tdclass="tg-yw4l">sdiff</td>
<tdclass="tg-yw4l">Shows two files side-by-side and highlights the differences.</td>
</tr>
<tr>
<tdclass="tg-yw4l">sed</td>
<tdclass="tg-yw4l">Stream editor for filtering and transforming text (from a file or a pipe input).</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>
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<tdclass="tg-yw4l">tac</td>
<tdclass="tg-yw4l">Concatenate and print files in reverse order. Opposite of cat command.</td>
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<tdclass="tg-yw4l">tail</td>
<tdclass="tg-yw4l">Show the last 10 lines of each specified file(s).</td>
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<tdclass="tg-yw4l">tailf</td>
<tdclass="tg-yw4l">Follow the growth of a log file. (Deprecated command)</td>
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<tdclass="tg-yw4l">talk</td>
<tdclass="tg-yw4l">A two-way screen-oriented communication utility that allows two user to exchange messages simultaneously.</td>
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<tdclass="tg-yw4l">talkd</td>
<tdclass="tg-yw4l">A remote user communication server for <em>talk</em>.</td>
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<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>
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<tdclass="tg-yw4l">taskset</td>
<tdclass="tg-yw4l">Set/retrieve a process’s CPU affinity.</td>
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<tdclass="tg-yw4l">tcpd</td>
<tdclass="tg-yw4l">Access control utility for internet services.</td>
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<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>
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<tdclass="tg-yw4l">tcpslice</td>
<tdclass="tg-yw4l">Extract pieces of tcpdump files or merge them.</td>
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<tdclass="tg-yw4l">tee</td>
<tdclass="tg-yw4l">Read from standard input and write to standard output and files.</td>
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<tdclass="tg-yw4l">telinit</td>
<tdclass="tg-yw4l">Change SysV runlevel.</td>
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<tdclass="tg-yw4l">telnet</td>
<tdclass="tg-yw4l">Telnet protocol user interface. Used to interact with another host using telnet.</td>
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<tdclass="tg-yw4l">telnetd</td>
<tdclass="tg-yw4l">A server for the telnet protocol.</td>
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<tdclass="tg-yw4l">test</td>
<tdclass="tg-yw4l">Check file type and compare values.</td>
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<tdclass="tg-yw4l">tftp</td>
<tdclass="tg-yw4l">User interface to the internet TFTP (Trivial File Transfer Protocol).</td>
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<tdclass="tg-yw4l">tftpd</td>
<tdclass="tg-yw4l">TFTP server.</td>
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<tdclass="tg-yw4l">time</td>
<tdclass="tg-yw4l">Run programs and summarize system resource usage.</td>
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<tdclass="tg-yw4l">timeout</td>
<tdclass="tg-yw4l">Execute a command with a time limit.</td>
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<tdclass="tg-yw4l">times</td>
<tdclass="tg-yw4l">Shows accumulated user and system times for the shell and it’s child processes.</td>
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<tdclass="tg-yw4l">tload</td>
<tdclass="tg-yw4l">Shows a graph of the current system load average to the specified tty.</td>
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<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>
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<tdclass="tg-yw4l">top</td>
<tdclass="tg-yw4l">Displays real-time view of processes running on the system.</td>
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<tdclass="tg-yw4l">touch</td>
<tdclass="tg-yw4l">Change file access and modification times.</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>
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<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>
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<tdclass="tg-yw4l">│</td>
<tdclass="tg-yw4l">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.</td>
<tdclass="tg-yw4l">The OR operator is used to chain commands. It will execute succeeded commands which follows and stops if the preceding command fails.</tr>
<tdclass="tg-yw4l">The AND operator is used to chain commands. It will execute commands only if the first command is successful</td>
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<tdclass="tg-yw4l">;</td>
<tdclass="tg-yw4l">Command separator [semicolon]. Used to separate multiple commands and execute all the ones that is successful.</td>
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<tdclass="tg-yw4l">&</td>
<tdclass="tg-yw4l">Run job in background[and]. A command followed by an & will run in the background.</td>
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<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>
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<tdclass="tg-yw4l"> >, >>, <</td>
<tdclass="tg-yw4l">Redirect a command's output or input into a file.</td>
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<tdclass="tg-yw4l">>|</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.</td>
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<tdclass="tg-yw4l">""</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>
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<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>
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<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>
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<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>
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<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>
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<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.
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<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>
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<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>
