Comprehensive Guide to Linux Commands from A to Z – 2023 Edition

This article serves as a comprehensive guide to Linux commands, summarizing commands from A to Z. It is recommended to bookmark it for reference or to fill in any gaps in your knowledge!

A

Command	Description
access	Used to check if a program can access a specified file, verifying if the file exists.
accton	Used to turn on or off accounting processes or to change the information in the accounting file.
aclocal	Used to automatically generate the aclocal.m4 file from the configure.in file.
acpi	Used to display battery status and other ACPI information.
acpi_available	Tests if the ACPI (Advanced Configuration and Power Interface) subsystem is available.
acpid	Provides intelligent power management, notifying user-space programs about ACPI events.
addr2line	Used to convert addresses to file names and line numbers.
agetty	The Linux version of getty, a Unix program that manages physical or virtual terminals to allow multi-user access.
alias	Indicates to the shell to replace one string with another when executing commands.
amixer	Command-line mixer for the ALSA (Advanced Linux Sound Architecture) sound card driver.
aplay	Command-line audio player for the ALSA sound card driver.
aplaymidi	Used to play standard MIDI (Musical Instrument Digital Interface) files by sending the contents of the MIDI file to the ALSA MIDI port.
apropos	Helps users when they do not remember the exact command but know some keywords related to its purpose or function.
apt	Provides a high-level CLI (Command Line Interface) for the package management system, designed as an interface for end users, compared to more specialized APT tools like apt-cache and apt-get.
apt-get	A command-line tool that helps manage packages in Linux.
aptitude	Provides a highly integrated interface to interact with the machine’s package manager.
ar	Used to create, modify, and extract files from archives.
arch	Used to print the computer architecture.
arp	Manipulates the system’s ARP cache, allowing a complete dump of the ARP cache.
aspell	Used as a spell checker in Linux.
atd	A job scheduling daemon that runs scheduled jobs for later execution.
atrm	Used to remove specified jobs; to remove a job, its job number is passed in the command.
atq	Displays a list of pending jobs scheduled by the user.
autoconf	Used in Linux to generate configuration scripts.
autoheader	Used to create template files for C “#define” or any other template headers for configure.
automake	Used to automatically generate Makefile.in files that conform to GNU coding standards.
autoreconf	Used to create source code that can be automatically built for Unix-like systems.
autoupdate	Used to update the configure.in file in our Linux system to a newer version of Autoconf.
awk	A scripting language used for manipulating data and generating reports.

B

Command	Description
banner	Used to print uppercase ASCII strings to standard output.
basename	Removes directory information and suffix from a file name, i.e., prints the file name NAME and removes any leading directory components.
batch	Reads commands from standard input or a specified file and executes them when the system load level allows, i.e., when the average load is below 1.5.
bc	Command-line calculator.
bg	Used to place a foreground job in the background.
biff	Unix mail notification system that notifies the user on the command line when new mail arrives and tells who it is from.
bind	Used to set Readline key bindings and variables.
bison	A parser generator similar to yacc.
break	Used to terminate the execution of for, while, and until loops.
builtin	Used to run built-in shell commands, passing parameters (args) to it and obtaining the exit status.
bzcmp	Used to call the cmp utility on bzip2 compressed files.
bzdiff	Used to compare bzip2 compressed files.
bzgrep	Used to search for patterns or expressions in bzip2 compressed files.
bzip2	Used to compress and decompress files.
bzless	Starts faster for large files as it does not need to read the entire input file before starting.
bzmore	Acts as a CRT filter for viewing bzip2 compressed files, which are saved with a .bz2 suffix.

C

Command	Description
cal	Used to view the calendar for a specific month or the entire year; by default, it displays the calendar for the current month as output.
case	The best choice when we have to use multiple if/elif on a single variable.
cat	Reads data from a file and outputs its contents.
cc	Used to compile C language code and create executable files.
ccrypt	A command-line tool for data encryption and decryption.
cd	Called the change directory command. It is used to change the current working directory.
cfdisk	Displays or manipulates the disk partition table by providing a text-based “graphical” interface.
chage	Used to view and modify user password expiration information.
chattr	A filesystem command used to change file attributes in a directory.
chfn	Changes username and other details.
chgrp	Used to change the group ownership of files or directories.
chkconfig	Used to list all available services and view or update their runlevel settings.
chmod	Used to change the access mode of files.
chown	Used to change the owner or group of files.
chpasswd	Used to change the passwords of multiple users at once.
chroot	Used to change the root directory.
chrt	Used to manipulate the real-time attributes of processes.
chsh	Used to change the user’s login shell (current login shell).
chvt	Used to switch between different available TTY (TeleTYpewriter) terminals.
cksum	Used to display a CRC (Cyclic Redundancy Check) value, the byte size of a file, and the file name to standard output.
clear	Used to clear the terminal screen.
cmp	Used to compare two files byte by byte, helping you find out if the two files are the same.
col	Used to filter out reverse line feeds; the col utility simply reads from standard input and writes to standard output.
colcrt	Used to format text processor output for viewing on cathode ray tube displays.
colrm	Used to remove selected columns from a file.
column	Used to display the contents of a file in columns.
comm	Compares two sorted files line by line and writes to standard output the common lines and unique lines.
compress	Used to reduce file size; after compression, the file will be available and have a .Z extension.
continue	Used to skip the current iteration in for, while, and until loops.
cp	Used to copy files or a group of files or directories.
cpio	cpio stands for “copy in, copy out”; it is used to handle archive files such as *.cpio or *.tar, and this command can copy files to or from an archive.
cpp	The C compiler automatically uses it to transform programs before compilation.
cron	A software utility provided by Unix-like operating systems that automatically executes scheduled tasks at specified times.
crontab	A list of commands for scheduled tasks.
csplit	Used to split any file into multiple parts as needed by the user.
ctags	Provides quick access to files (e.g., quickly viewing function definitions).
cupsd	A scheduler for CUPS (Common Unix Printing System) that implements a printing system based on the Internet printing protocol.
curl	A tool for transferring data to or from a server using any supported protocol.
cut	Used to cut sections from each line of a file and write the result to standard output.
cvs	Used to store the history of files; whenever a file is corrupted or has any issues, “cvs” helps us revert to a previous version and recover our files.

D

Command	Description
date	Used to display the system date and time. It is also used to set the system’s date and time.
dc	Used to calculate arithmetic expressions. It computes expressions in postfix notation.
dd	A command-line utility for Unix and Unix-like operating systems, primarily aimed at converting and copying files.
declare	Used to declare shell variables and functions, set their attributes, and display their values.
depmod	Used to generate a list of dependency descriptions for kernel modules and their associated mapping files.
df	Used to display information about the total and available space on the filesystem.
diff	Used to show differences between files by comparing them line by line.
diff3	Used to compare three files line by line.
dir	Used to list the contents of a directory.
dirname	Used to remove the trailing slash from NAME and print the remaining part.
dirs	Used to display the list of currently remembered directories.
disable	Used to stop a printer or class.
dmesg	Used to check the kernel ring buffer and print kernel messages.
dmidecode	Used when a user wants to retrieve system hardware-related information such as processor, RAM (DIMM), BIOS details, etc., in a readable format.
domainname	Used to return the network information system (NIS) domain name of the host.
dos2unix	Converts DOS text files to UNIX format.
dosfsck	Diagnoses issues with the MS-DOS filesystem and attempts to fix them.
dstat	Used to retrieve information or statistics from the system’s components (e.g., network connections, IO devices, or CPU).
du	Used to track files and directories that are taking up excessive disk space.
dump	Used to back up the filesystem to a storage device.
dumpe2fs	Used to print superblock and block group information of the filesystem present on a device.
dumpkeys	Used to dump the keyboard translation table.

E

Command	Description
echo	Used to display the text/string line passed as a parameter.
ed	Used to start the ed text editor, a line-based text editor with a minimal interface that reduces the complexity of handling text files, i.e., creating, editing, displaying, and manipulating files.
egrep	Treats patterns as extended regular expressions and prints lines that match the pattern.
eject	Uses software to eject removable media (usually CD-ROMs, floppy disks, tapes, or JAZ or ZIP disks).
emacs	An editor with a simple user interface. Additionally, this editor does not have an insert mode; it only has an edit mode.
enable	Used to start a printer or class.
env	Used to print environment variables. It is also used to run utilities or commands in a custom environment.
eval	Built-in command used to execute parameters as shell commands.
ex	A text editor in Linux, also known as the line editor mode of the vi editor.
exec	Used to execute commands from bash itself.
exit	Used to exit the currently running shell.
expa	Converts tabs to spaces in a file; when no file is specified, it reads from standard input.
expect	This command or scripting language is suitable for scripts that require user input, automating tasks by providing input.
export	A bash shell BUILTINS command, meaning it is part of the shell, marking environment variables to be exported to subprocesses.
expr	Evaluates a given expression and displays its corresponding output.

F

Command	Description
factor	Used to print the prime factors of a given number, provided from the command line or read from standard input.
fc	Used to list, edit, or re-execute commands previously entered into the interactive shell.
fc-cache	Scans font directories and builds font caches for applications using fontconfig for font handling.
fc-list	Used to list available fonts and font styles; with formatting options, it can filter and organize the list of all fonts.
fdisk	Format disk is a dialog-driven command in Linux used to create and manipulate disk partition tables.
fg	Used to bring a background job to the foreground.
fgrep	Used to search for fixed strings in files.
file	Used to determine the type of a file; .file types can be human-readable (e.g., ‘ASCII text’) or MIME types (e.g., ‘text/plain; charset=us-ascii’).
find	Used to find files and directories and perform subsequent operations on them.
finger	A user information lookup command that provides details about all logged-in users.
fmt	Acts as a formatter to simplify and optimize text files.
fold	Wraps each line in the input file to fit a specified width and prints it to standard output.
for	Used to repeat a set of commands for each element present in a list.
free	Displays the total amount of available space and the amount of memory and swap memory used in the system, as well as the buffers used by the kernel.
Fun	Used to draw various types of patterns on the terminal.
function	Used to create functions or methods.

G

Command	Description
g++	Used for preprocessing, compiling, assembling, and linking source code to generate executable files.
gawk	Used for pattern scanning and processing language.
gcc	The GNU Compiler Collection primarily used to compile C and C++ languages. It can also be used to compile Objective C and Objective C++.
gdb	The GNU Debugger helps debug programs written in C, C++, Ada, Fortran, etc.
getent	Used to get entries from many important text files called databases.
gpasswd	Used to manage /etc/group and /etc/gshadow.
grep	Searches for specific character patterns in files and displays all lines containing that pattern.
groupadd	Used to create new user groups.
groupdel	Used to delete existing groups.
groupmod	Used to modify or change existing groups on the Linux system.
groups	A group is a collection of users. Groups make it easier to manage users with the same security and access rights.
grpck	Verifies the integrity of group information. It checks that all entries in /etc/group and /etc/gshadow have the correct format and contain valid data.
grpconv	Used to convert to shadow groups. The grpconv command creates a gshadow from the group and an optional existing gshadow.
gs	This command calls Ghostscript, an interpreter for Adobe Systems’ PostScript and Portable Document Format (PDF) languages.
gunzip	Used to compress or expand files or lists of files in Linux.
gzexe	Used to compress executable files, also used to automatically decompress and execute files.
gzip	This command compresses files. Each individual file is compressed into a single file.

H

Command	Description
halt	Used to instruct hardware to stop all CPU functions, which will restart or stop the system.
hash	Used to maintain a hash table of recently executed programs.
hdparm	Used to obtain statistics about hard disks, change write intervals, sound management, and DMA settings.
Head	Prints the first N data of the given input.
help	Displays information about shell built-in commands.
hexdump	Used to filter and display specified files or standard input in a human-readable specified format.
history	Used to view previously executed commands.
host	Used for DNS (Domain Name System) lookup operations.
hostid	Used to display the Host’s ID in hexadecimal format.
hostname	Used to get the DNS (Domain Name System) name and set the system’s hostname or NIS (Network Information System) domain name.
hostnamectl	Provides the appropriate API to control the hostname of the Linux system and change its related settings.
htop	Allows users to interactively monitor important resources or server processes in real-time.
hwclock	Utility for accessing the hardware clock, also known as the real-time clock (RTC).

I

Command	Description
iconv	Used to convert text from one encoding to another.
id	Used to find out the username and group name, as well as the numeric ID (UID or GID) of the current user or any other user on the server.
if	Used to execute commands based on conditions.
ifconfig	Used to configure kernel-resident network interfaces.
iftop	A network analysis tool used by system administrators to view bandwidth-related statistics.
ifup	Starts network interfaces, allowing data transmission and reception.
import	Used to capture screenshots of any active pages we have and output them as image files.
info	Reads documentation in info format, providing detailed information about commands.
insmod	Used to insert modules into the kernel.
install	Used to copy files and set attributes.
iostat	Used to monitor system input/output statistics for devices and partitions.
iotop	Used to display and monitor disk IO usage details, even providing a table of existing IO usage by processes.
ip	Used to perform multiple network management tasks.
ipcrm	Used to remove some IPC (Inter-Process Communication) resources. It eliminates IPC objects and their associated data structures from the system.
ipcs	Displays information about inter-process communication facilities that the calling process has read access to.
iptables	Used to set up and maintain tables for the Netfilter firewall for IPv4, included in the Linux kernel.
iptables-save	Saves the current iptables rules to a user-specified file for later use when needed.
iwconfig	Used to display parameters and wireless statistics extracted from /proc/net/wireless.

J

Command	Description
join	Used to join lines of two files based on key fields present in both files.
journalctl	Used to view systemd, kernel, and journal logs.

K

Command	Description
kill	Used to manually terminate processes. The kill command sends a signal to terminate the process.

L

Command	Description
last	Used to display a list of all users who have logged in and out since the creation of the file /var/log/wtmp.
less	Used to view the contents of text files one page (one screen) at a time.
let	Used to calculate arithmetic expressions of shell variables.
ln	Used to create links between files.
locate	Used to find files by name.
look	Displays lines that begin with a given string.
lsblk	Used to display detailed information about block devices, which are essentially files representing devices connected to the PC (except for RAM disks).
lshw	Used to generate detailed information about the system hardware configuration from various files under the /proc directory.
lsmod	Used to display the status of modules in the Linux kernel. It results in a list of loaded modules.
lsof	Provides a list of open files.
lsusb	Used to display information about the USB bus and its connected devices.

M

Command	Description
mailq	This command in Linux prints the mail queue, i.e., a list of messages in the mail queue.
man	Used to display the user manual for any command that can be run in the terminal.
md5sum	Used to verify data integrity using MD5 (Message-Digest Algorithm 5).
mkdir	Allows users to create directories. This command can create multiple directories at once.
modinfo	Used to display information about Linux kernel modules.
more	Used to view text files at the command prompt, displaying one screen at a time (e.g., log files) when the file is large.
mount	Used to mount filesystems found on devices to a tree structure with “/” as the root (Linux filesystem).
mpstat	Used to report processor-related statistics.
mv	Used to move one or more files or directories from one place to another in UNIX-like filesystems.

N

Command	Description
nc(netcat)	It is one of the powerful network tools, security tools, or network monitoring tools.
netstat	Displays various network-related information such as network connections, routing tables, interface statistics, masquerade connections, multicast memberships, etc.
nmcli	Used to control NetworkManager. The nmcli command can also be used to display the status of network devices, create, edit, activate/deactivate, and delete network connections.
nslookup	A network management tool used to query the Domain Name System (DNS) for domain name or IP address mappings or any other specific DNS records.

O

Command	Description
od	Used to convert the input content into different formats in octal format by default.

P

Command	Description
passwd	Used to change user account passwords.
paste	Used to horizontally concatenate files (parallel merge) by outputting lines composed of lines from each specified file, separated by tabs, to standard output.
pidof	Used to find the process ID of a specific running program.
ping	Used to check network connectivity between a host and a server/host.
pinky	A user information lookup command that provides details about all logged-in users.
pmap	Used to display the memory mapping of processes. Memory mapping indicates how memory is distributed.
poweroff	Sends an ACPI signal indicating the system to shut down power.
printf	Used to display given strings, numbers, or any other format specifiers in the terminal window.
ps	Used to list currently running processes and their PIDs, along with some other information depending on different options.
pwd	Prints the path of the working directory, starting from the root.

R

Command	Description
ranlib	Used to generate an index for archives.
rcp	Used to copy files from one computer to another.
read	Reads the total number of bytes from the specified file descriptor into a buffer.
readelf	Used to obtain information about ELF (Executable and Linkable Format) files.
readlink	Used to print the resolved symbolic link or canonical file name.
reboot	Instructs the system to restart or reboot.
rename	Used to rename files according to a regular expression perlexpr.
reset	Used to initialize the terminal. This is useful when the terminal is in an abnormal state after a program terminates.
restore	Used to restore files from backups created using dump.
return	Used to exit shell functions.
rev	Used to reverse lines by character.
rm	Used to remove files, directories, symbolic links, and other objects from UNIX-like filesystems.
rmdir	Used to remove empty directories from the filesystem in Linux.
rmmod	Used to remove modules from the kernel.
route	Used when you want to use the IP/kernel routing table.
rsync	Synchronizes files and directories between two hosts or machines.

S

Command	Description
sar	Used to monitor resources of the Linux system, such as CPU usage, memory usage, I/O device consumption, etc.
scp	Used to securely copy files between servers.
screen	Provides the ability to start and use multiple shell sessions from a single ssh session.
script	Used to make a typescript or record all terminal activity.
scriptreplay	Used to replay the typescript/terminal activity stored in the log file of script command.
sdiff	Used to compare two files and write the results to standard output in side-by-side format.
sed	Used for searching, filtering, text replacement, substitution, and text operations such as inserting, deleting searches, etc.
select	Used to create a numbered menu from which the user can select an option.
seq	Used to generate numbers from FIRST to LAST in steps of INCREMENT.
setsid	Used to run a program in a new session.
shift	Moves/moves command line parameters to the left by one position.
showkey	Prints the scan code or key code or “ascii” code of each key pressed to standard output.
shred	Used to securely delete files from the hard disk.
shutdown	Used to safely shut down the system.
sleep	Used to create virtual jobs. Virtual jobs help delay execution.
source	Used to read and execute the contents of a file (usually a set of commands) passed as parameters in the current shell script.
sort	Used to sort files, arranging records in a specific order.
split	Used to split large files into smaller files.
ssh	Protocol for securely connecting to remote servers/systems.
strace	It is one of the most powerful process monitoring, diagnostic, and teaching tools in Linux.
stty	Used to change and print terminal line settings.
sudo	Acts as a prefix for commands that are only allowed to be run by superusers.
sum	Used to find checksums and count blocks in files.
sync	Used to synchronize cached writes to persistent storage.
systemctl	Used to check and control the status of the “systemd” system and service manager.

T

Command	Description
tac	Used to concatenate and print files in reverse.
tail	Prints the last N data of the given input.
tar	Used to create and extract archive files.
tee	Reads standard input and writes it to standard output and one or more files.
time	Used to execute commands and print a summary of the real, user CPU time, and system CPU time spent executing the command when it terminates.
top	Provides a dynamic real-time view of the running system.
touch	Used to create, change, and modify file timestamps.
tr	Used to translate or delete characters.
tracepath	Used to trace the path to a destination, discovering the MTU along this path.
traceroute	Prints the route that packets take to reach a host.
tree	A recursive directory listing program that produces a deep-indented list of files.
tty	Displays information related to the terminal, printing the file name of the terminal connected to standard input.
type	Used to describe how its parameters would be translated if used as a command.

U

Command	Description
uname	Displays information about the system.
unexpand	Converts each space to a tab, writing the generated output to standard output.
uniq	Used to report or filter out duplicate lines in files.
unix2dos	Converts Unix text files to DOS format.
until	Used to execute a set of commands as long as the exit status of the last command in “until” is not zero.
uptime	Used to find out how long the system has been active (running).
useradd	Used to add user accounts to your system.
usermod	Used to change user attributes via command line in Linux.
username	Retrieves the username and its configuration.
users	Used to display the usernames of users currently logged into the current host.
userdel	Used to delete user accounts and related files.

V

Command	Description
vi	The default editor that comes with the UNIX operating system, known as the visual editor.
vmstat	A command for monitoring system performance, capable of monitoring information about processes, memory, paging, block IO, disk, and CPU scheduling.
vnstat	Used by system administrators to monitor network parameters, such as bandwidth consumption or certain traffic flowing in or out.

W

Command	Description
w	Used to display who is logged in and what they are doing.
wall	Displays messages, file contents, or other standard input on the terminals of all currently logged-in users.
watch	Used to execute programs periodically, displaying output in full screen.
wc	Used to find the number of lines, words, byte sizes, and character counts in files specified in file parameters.
wget	Used to download files from servers, even allowing users to work in the background without interrupting current processes.
whatis	Used to get a one-line description of manual pages.
which	Used to locate executable files associated with a given command by searching in the path environment variable.
while	Used to repeatedly execute a set of commands as long as COMMAND returns true.
who	Used to get information about currently logged-in users on the system.
whoami	Displays the username of the current user when this command is called.
write	Allows users to communicate with other users by copying lines from one user’s terminal to another.

X

Command	Description
xargs	Used to build and execute commands from standard input. It converts input received from standard input into command parameters.
xdg-open	Used to open files or URLs in the user’s preferred application.

Y

Command	Description
yes	Used to print a continuous output stream of the given STRING. If STRING is not mentioned, it prints ‘y’.

Z

Command	Description
zdiff	Used to call the diff program on files compressed with gzip.
zdump	Used to print the current time in the specified zone, or you can say print the current time in each zone name specified on the command line.
zgrep	Used to search for expressions from a given file, even if it is compressed.
zip	A compression and file packaging utility for Unix, where each file is stored in a single .zip file with a .zip extension.

Translated from the Network Technology Alliance site

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