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Linux Commands

  • Difficulty Level : Medium
  • Last Updated : 29 May, 2020

Linux is a Unix-Like operating system. All the Linux/Unix commands are run in the terminal provided by the Linux system. This terminal is just like the command prompt of Windows OS. Linux/Unix commands are case-sensitive. The terminal can be used to accomplish all Administrative tasks. This includes package installation, file manipulation, and user management. Linux terminal is user-interactive. The terminal outputs the results of commands which are specified by the user itself. Execution of typed command is done only after you press the Enter key.

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CommandsDescription

accessUsed to check whether the calling program has access to a specified file. It can be used to check whether a file exists or not
acctonUsed to turn on or turn off the process for accounting or change info process accounting file
aclocalUsed to automatically generate aclocal.m4 files from configure.in file
acpiUsed to display the battery status and other ACPI information
acpi_availableTests whether ACPI (Advanced Configuration and Power Interface) subsystem is available or not
acpidIt provides intelligent power management on a system and is used to notify the user-space programs about the ACPI events
addr2lineUsed to convert addresses into file names and line numbers
agettyIt is a Linux version of getty, which is a Unix program running on a host computer that manages physical or virtual terminals to allow multi-user access
aliasInstructs the shell to replace one string with another string while executing the commands
amixerIt is a command-line mixer for ALSA(Advanced Linux Sound Architecture) sound-card driver
aplayIt is a command-line audio player for ALSA(Advanced Linux Sound Architecture) sound card drivers.
aplaymidiUsed to play standard MIDI(Musical Instrument Digital Interface) files, by sending the content of a MIDI file to an ALSA(Advanced Linux Sound Architecture) MIDI port
aproposIt helps the user when they don’t remember the exact command but knows a few keywords related to the command that define its uses or functionality
aptProvides a high-level CLI (Command Line Interface) for the package management system and is intended as an interface for the end user which enables some options better suited for interactive usage by default compared to more specialized APT tools like apt-cache and apt-get
apt-getIt is a command-line tool which helps in handling packages in Linux
aptitudeOpens up a highly built-in interface to interact with the package manager of the machine
arUsed to create, modify and extract the files from the archives
archUsed to print the computer architecture
arpIt manipulates the System’s ARP cache. It also allows a complete dump of the ARP cache
aspellUsed as a spell checker in Linux
atdIt is a job scheduler daemon that runs jobs scheduled for later execution
atrmUsed to remove the specified jobs. To remove a job, its job number is passed in the command
atqIt displays the list of pending jobs which are scheduled by the user
autoconfUsed in Linux to generate configuration scripts
autoheaderUsed to create a template file of C “#define” or any other template header for configure to use
automakeUsed for automatically generating Makefile.in files compliant with the set GNU Coding Standards
autoreconfUsed to create automatically buildable source code for Unix-like systems
autoupdateUsed to update configure.in file in our Linux system to a newer Autoconf.
awkIt is a scripting language used for manipulating data and generating reports

bannerUsed to print the ASCII character string in large letter to standrad output
basenameIt strips directory information and suffixes from file names i.e. it prints the file name NAME with any leading directory components removed
batchUsed to read commands from standard input or a specified file and execute them when system load levels permit i.e. when the load average drops below 1.5
bcUsed for command line calculator
bgUsed to place foreground jobs in background
biffA mail notification system for unix that notifies the user at the command line when new mail arrives and tells from whom it is
bindUsed to set Readline key bindings and variables
bisonIt is basically a parser generator similar to yacc
breakUsed to terminate the execution of for loop, while loop and until loop
builtinUsed to run a shell builtin, passing it arguments(args), and also to get the exit status
bzcmpUsed to invoke the cmp utility on bzip2 compressed files
bzdiffUsed to compare the bzip2 compressed files
bzgrepUsed to search for a pattern or an expression but inside a bzip2-compressed file
bzip2Used to compress and decompress the files
bzlessIt does not have to read the entire input file before starting, so with a large file, it starts up faster
bzmoreUsed as a filter for CRT viewing of bzip2 compressed files, which are saved with .bz2 suffix

calUsed to see the calendar of a specific month or a whole year. By default, it shows current month’s calendar as output
caseIt is the best alternative when we had to use multiple if/elif on a single variable
catReads data from file and gives their content as output. It helps us to create, view, concatenate files
ccIt is used to compile the C language codes and create executables
ccryptIt is a command line tool for encryption and decryption of data
cdKnown as change directory command. It is used to change current working directory
cfdiskIt displays or manipulates the disk partition table by providing a text-based “graphical” interface
chageUsed to view and change the user password expiry information
chattrIt is a file system command which is used for changing the attributes of a file in a directory
chfnIt allows you to change a user’s name and other details easily. chfn stands for Change finger
chgrpUsed to change the group ownership of a file or directory
chkconfigUsed to list all available services and view or update their run level settings
chmodUsed to change the access mode of a file
chownUsed to change the file Owner or group
chpasswdUsed to change password for multiple users at a time
chrootUsed to change the root directory
chrtUsed for manipulating the real-time attributes of a process
chshUsed to change the user’s login shell(currently login shell)
chvtUsed to switch between the different TTY (TeleTYpewriter) terminals available
cksumUsed to display a CRC(Cyclic Redundancy Check) value, the byte size of the file and the name of the file to standard output
clearUsed to clear the terminal screen
cmpUsed to compare the two files byte by byte and helps you to find out whether the two files are identical or not
colIt is used to filter out reverse line feeds. The col utility simply reads from the standard input and writes to standard output
colcrtUsed to format the text processor output so that it can be viewed on Cathode Ray Tube displays
colrmRemoves selected columns from a file
columnUsed to display the contents of a file in columns
commCompares two sorted files line by line and write to standard output; the lines that are common and the lines that are unique
compressUsed to reduce the file size. After compression, the file will be available with an added .Z extension
continueUsed to skip the current iteration in for, while and until loop
cpUsed to copy files or group of files or directory
cpiocpio stands for “copy in, copy out“. It is used for processing the archive files like *.cpio or *.tar. This command can copy files to and from archives
cppIt is automatically used by C compiler to transform your program before compilation
cronA software utility, offered by Linux-like operating system which automates the scheduled task at a predetermined time
crontabA list of commands that you want to run on a regular schedule, and also the name of the command used to manage that list
csplitUsed to split any file into many parts as required by the user
ctagsIt allows quick access across the files (For example quickly seeing definition of a function)
cupsdIt is a type of scheduler for CUPS (Common Unit Printing System). It implements the printing system on the basis of the Internet Printing Protocol
curlA tool to transfer data to or from a server, using any of the supported protocols
cutFor cutting out the sections from each line of files and writing the result to standard output
cvsUsed to store the history of a file. Whenever a file gets corrupted or anything goes wrong “cvs” help us to go back to the previous version and restore our file

dateUsed to display the system date and time. It is also used to set date and time of the system
dcUsed to evaluate arithmetic expressions. It evaluates expressions in the form of a postfix expression
ddIt is a command-line utility for Unix and Unix-like operating systems whose primary purpose is to convert and copy files
declareUsed to declare shell variables and functions, set their attributes and display their values
depmodUsed to generate a list of dependency description of kernel modules and its associated map files
dfUsed to display information related to file systems about total space and available space
diffUsed to display the differences in the files by comparing the files line by line
diff3Used to compare the three files line by line
dirUsed to list the contents of a directory
dirnameUsed to remove the trailing forward slahes “/” from the NAME and prints the remaining portion
dirsUsed to display the list of currently remembered directories
disableUsed to stop the printers or classes
dmesgUsed to examine the kernel ring buffer and print the message buffer of kernel
dmidecodeUsed 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
domainnameUsed to return the Network Information System (NIS) domain name of the host
dos2unixConverts a DOS text file to UNIX format
dosfsckDiagnoses MS-DOS file system for problems and attempts to repair them
dstatUsed to retrieve information or statistics form components of the system such as network connections, IO devices, or CPU, etc.
duUsed to track the files and directories which are consuming excessive amount of space on hard disk drive
dumpUsed to backup the filesystem to some storage device
dumpe2fsUsed to print the super block and blocks group information for the filesystem present on device
dumpkeysUsed for the dump keyboard translation tables



echoUsed to display line of text/string that are passed as an argument
edUsed for launching the ed text editor which is a line-based text editor with a minimal interface which makes it less complex for working on text files i.e creating, editing, displaying and manipulating files
egrepIt treats the pattern as an extended regular expression and prints out the lines that match the pattern
ejectIt allows ejecting a removable media (typically a CD-ROM, floppy disk, tape, or JAZ or ZIP disk) using the software
emacsIt is a editor having simple user interface. Also, there is no insert mode in this editor. It only have editing mode.
enableUsed to start the printers or classes
envUsed to either print environment variables. It is also used to run a utility or command in a custom environment
evalBuilt-in command used to execute arguments as a shell command
exIt is a text editor in Linux which is also termed as the line editor mode of the vi editor
execUsed to execute a command from the bash itself
exitUsed to exit the shell where it is currently running
expandAllows you to convert tabs into spaces in a file and when no file is specified it reads from standard input
expectThis command or scripting language works with scripts that expect user inputs. It automates the task by providing inputs
exportIt is bash shell BUILTINS commands, which means it is part of the shell. It marks an environment variables to be exported to child-processes
exprIt evaluates a given expression and displays its corresponding output

factorUsed to print the prime factors of the given numbers, either given from command line or read from standard input
fcUsed to list, edit or re-execute the commands previously entered into an interactive shell
fc-cacheIt scans the font directories and build font cache for applications which use fontconfig for their font handling
fc-listIt is used to list the available fonts and font styles. Using the format option, the list of all fonts can be filtered and sorted out
fdiskFormat disk is a dialog-driven command in Linux used for creating and manipulating disk partition table
fgUsed to put a background job in foreground
fgrepUsed to search for the fixed-character strings in a file
fileUsed to determine the type of a file. .file type may be of human-readable(e.g. ‘ASCII text’) or MIME type(e.g. ‘text/plain; charset=us-ascii’)
findUsed to find files and directories and perform subsequent operations on them
fingerIt is a user information lookup command which gives details of all the users logged in.
fmtWorks as a formatter for simplifying and optimizing text files
foldIt wraps each line in an input file to fit a specified width and prints it to the standard output
forUsed to repeatedly execute a set of command for every element present in the list
freeDisplays the total amount of free space available along with the amount of memory used and swap memory in the system, and also the buffers used by the kernel
FunUsed to draw various type of patterns on the terminal
functionUsed to create functions or methods

g++Used for preprocessing, compilation, assembly and linking of source code to generate an executable file
gawkUsed for pattern scanning and processing language
gccGNU Compiler Collections is used to compile mainly C and C++ language. It can also be used to compile Objective C and Objective C++
gdbGNU Debugger tool helps to debug the programs written in C, C++, Ada, Fortran, etc.
getentUsed to get the entries in a number of important text files called databases
gpasswdUsed to administer the /etc/group and /etc/gshadow
grepSearches a file for a particular pattern of characters, and displays all lines that contain that pattern
groupaddUsed to create a new user group
groupdelUsed to delete a existing group
groupmodUsed to modify or change the existing group on Linux system
groupsGroups are the collection of users. Groups make it easy to manage users with the same security and access privileges
grpckIt verifies the integrity of the groups information. It checks that all entries in /etc/group and /etc/gshadow have the proper format and contain valid data
grpconvIt is used to convert to shadow groups. The grpconv command creates a gshadow from the group and an optionally existing gshadow
gsThis command invokes Ghostscript, which is an interpreter of Adobe Systems PostScript and Portable Document Format(PDF) languages
gunzipUsed to compress or expand a file or a list of files in Linux
gzexeUsed to compress executable files and also used to automatically uncompress and execute the files
gzipThis command compresses files. Each single file is compressed into a single file.

haltUsed to instruct the hardware to stop all the CPU functions. Basically, it reboots or stops the system.
hashUsed to maintain a hash table of recently executed programs
hdparmUsed to get statistics about the hard disk, alter writing intervals, acoustic management, and DMA settings
HeadPrints the top N number of data of the given input
helpDisplays information about shell built-in commands
hexdumpUsed to filter and display the specified files, or standard input in a human readable specified format
historyUsed to view the previously executed command
hostUsed for DNS (Domain Name System) lookup operations
hostidUsed to displays the Host’s ID in hexadecimal format
hostnameUsed to obtain the DNS(Domain Name System) name and set the system’s hostname or NIS(Network Information System) domain name.
hostnamectlProvides a proper API used to control Linux system hostname and change its related settings
htopIt is a command line utility that allows the user to interactively monitor the system’s vital resources or server’s processes in real time
hwclockUtility for accessing the hardware clock, also called Real Time Clock (RTC)

iconvUsed to convert some text in one encoding into another encoding
idUsed to find out user and group names and numeric ID’s (UID or group ID) of the current user or any other user in the server
ifUsed to execute commands based on conditions
ifconfigUsed to configure the kernel-resident network interfaces.
iftopIt is a network analyzing tool used by system administrators to view the bandwidth related stats
ifupIt basically brings the network interface up, allowing it to transmit and receive data
importUsed for capturing a screenshot for any of the active pages we have and it gives the output as an image file
infoReads documentation in the info format. It will give detailed information for a command when compared with the main page
insmodUsed to insert modules into the kernel
installUsed to copy files and set attributes
iostatUsed for monitoring system input/output statistics for devices and partitions
iotopUsed to display and monitor the disk IO usage details and even gets a table of existing IO utilization by the process
ipUsed for performing several network administration tasks
ipcrmUsed to remove some IPC(Inter-Process Communication) resources. It eliminates the IPC objects and their associated data structure form the system
ipcsShows information on the inter-process communication facilities for which the calling process has read access
iptablesUsed to set up and maintain tables for the Netfilter firewall for IPv4, included in the Linux kernel
iptables-saveIt will save the current iptables rules in a user specified file, that can be used later when the user wants
iwconfigUsed to display the parameters, and the wireless statistics which are extracted from /proc/net/wireless

joinIt is a command line utility for joining lines of two files based on a key field present in both the files
journalctlUsed to view systemd, kernal and journal logs

killUsed to terminate processes manually. kill command sends a signal to a process which terminates the process

lastUsed to display the list of all the users logged in and out since the file /var/log/wtmp was created
lessUsed to read contents of text file one page(one screen) per time
letUsed to evaluate arithmetic expressions on shell variables
lnUsed to create links between files
locateUsed to find the files by name
lookShows the lines beginning with a given string
lsblkUsed to display details about block devices and these block devices(Except ram disk) are basically those files that represent devices connected to the pc.
lshwUsed to generate the detailed information of the system’s hardware configuration from various files in the /proc directory
lsmodUsed to display the status of modules in the Linux kernel. It results in a list of loaded modules
lsofProvides a list of files that are opened
lsusbUsed to display the information about USB buses and the devices connected to them

mailqThis command in Linux prints the mail queue i.e the list of messages that are there in the mail queue
manUsed to display the user manual of any command that we can run on the terminal
md5sumTo verify data integrity using MD5 (Message Digest Algorithm 5)
mkdirAllows the user to create directories. This command can create multiple directories at once
modinfoUsed to display the information about a Linux Kernel module
moreUsed to view the text files in the command prompt, displaying one screen at a time in case the file is large (For example log files)
mountUsed to mount the filesystem found on a device to big tree structure(Linux filesystem) rooted at ‘/‘
mpstatUsed to report processor related statistics.
mvUsed to move one or more files or directories from one place to another in file system like UNIX



nc(netcat)It is one of the powerful networking tool, security tool or network monitoring tool.
netstatDisplays various network related information such as network connections, routing tables, interface statistics, masquerade connections, multicast memberships, etc.
nmcliUsed for controlling NetworkManager. nmcli commnad can also be used to display network device status, create, edit, activate/deactivate, and delete network connections
nslookupIt is a network administration tool for querying the Domain Name System (DNS) to obtain domain name or IP address mapping or any other specific DNS record

odUsed to convert the content of input in different formats with octal format as the default format

passwdUsed to change the user account passwords
pasteUsed to join files horizontally (parallel merging) by outputting lines consisting of lines from each file specified, separated by tab as delimiter, to the standard output
pidofUsed to find out the process IDs of a specific running program
pingUsed to check the network connectivity between host and server/host
pinkyIt is a user information lookup command which gives details of all the users logged in. Unlike finger, in the pinky, you may trim the information of your interest.
pmapUsed to display the memory map of a process. A memory map indicates how memory is spread out
poweroffSends an ACPI signal which instructs the system to power down
printfUsed to display the given string, number or any other format specifier on the terminal window
psUsed to list the currently running processes and their PIDs along with some other information depends on different options
pwdIt prints the path of the working directory, starting from the root

ranlibUsed to generate index to archive
rcpUsed to copy files from one computer to another computer
readReads up the total number of bytes from the specified file descriptor into the buffer
readelfUsed to get information of ELF(Executable and Linkable Format) Files
readlinkUsed to print resolved symbolic links or canonical file names
rebootInstructs the system to restart or reboot
renameUsed to rename the named files according to the regular expression perlexpr
resetUsed to initialize the terminal. This is useful once a program dies leaving a terminal in an abnormal state
restoreUsed for restoring files from a backup created using dump
returnUsed to exit from a shell function.
revUsed to reverse the lines characterwise
rmUsed to remove objects such as files, directories, symbolic links and so on from the file system like UNIX
rmdirUsed to remove empty directories from the filesystem in Linux
rmmodUsed to remove a module from the kernel
routeUsed when you want to work with the IP/kernel routing table
rsyncIt is a software utility for Unix-Like systems that efficiently sync files and directories between two hosts or machines

sarUsed to monitor Linux system’s resources like CPU usage, Memory utilization, I/O devices consumption, etc.
scpUsed to copy file(s) between servers in a secure way.
screenProvides the ability to launch and use multiple shell sessions from a single ssh session
scriptUsed to make typescript or record all the terminal activities
scriptreplayUsed to replay a typescript/terminal_activity stored in the log file that was recorded by the script command
sdiffUsed to compare two files and then writes the results to standard output in a side-by-side format
sedUsed for finding, filtering, text substitution, replacement and text manipulations like insertion, deletion search etc.
selectUsed to create a numbered menu from which a user can select an option
seqUsed to generate numbers from FIRST to LAST in steps of INCREMENT
setsidUsed to run a program in a new session
shiftShifts/moves the command line arguments to one position left.
showkeyprints to standard output either the scan codes or the key code or the `ascii’ code of each key pressed
shredUsed in order to delete a file completely from hard disk
shutdownUsed to shutdown the system in a safe way
sleepUsed to create a dummy job. A dummy job helps in delaying the execution
sourceUsed to read and execute the content of a file(generally set of commands), passed as an argument in the current shell script
sortUsed to sort a file, arranging the records in a particular order
splitUsed to split large files into smaller files
sshProtocol used to securely connect to a remote server/system
straceIt is one of the most powerful process monitoring, diagnostic, instructional tool of Linux.
sttyUsed to change and print terminal line settings
sudoUsed as a prefix of some command that only superuser are allowed to run
sumUsed to find checksum and count the blocks in a file
syncUsed to synchronize cached writes to persistent storage
systemctlUsed to examine and control the state of “systemd” system and service manager

tacUsed to concatenate and print files in reverse
TailPrints the last N number of data of the given input
tarUsed to create Archive and extract the Archive files
teeReads the standard input and writes it to both the standard output and one or more files
timeUsed to execute a command and prints a summary of real-time, user CPU time and system CPU time spent by executing a command when it terminates
topProvides a dynamic real-time view of the running system
touchUsed to create, change and modify timestamps of a file
trIt is a command line utility for translating or deleting characters
tracepathUsed to traces path to destination discovering MTU along this path
traceroutePrints the route that a packet takes to reach the host
TreeA recursive directory listing program that produces a depth-indented listing of files
ttyIt displays the information related to terminal. It basically prints the file name of the terminal connected to standard input
typeUsed to describe how its argument would be translated if used as commands

unameDisplays the information about the system
unexpandConverts each spaces into tabs writing the produced output to the standard output
uniqIt is a command line utility that reports or filters out the repeated lines in a file
unix2dosConverts a Unix text file to DOS format
untilUsed to execute a set of commands as long as the final command in the ‘until’ Commands has an exit status which is not zero
UptimeUsed to find out how long the system is active (running)
useraddUsed to add user accounts to your system
usermodUsed to change the properties of a user in Linux through the command line
usernameIt provides a set of commands to fetch username and its configurations from the Linux host
usersUsed to show the user names of users currently logged in to the current host
userdelUsed to delete a user account and related files

viIt is the default editor that comes with the UNIX operating system is called visual editor.
vmstatIt is a performance monitoring command of the system as it gives the information about processes, memory, paging, block IO, disk and CPU scheduling
vnstatUsed by system administrators in order to monitor network parameters such as bandwidth consumption or maybe some traffic flowing in or out

wUsed to show who is logged on and what they are doing
wallDisplays a message, or the contents of a file, or otherwise its standard input, on the terminals of all currently logged in users
watchUsed to execute a program periodically, showing output in fullscreen
wcUsed to find out number of lines, word count, byte and characters count in the files specified in the file arguments
WgetUsed to download files from the server even when the user has not logged on to the system and it can work in background without hindering the current process
whatisUsed to get a one-line manual page descriptions
whichUsed to locate the executable file associated with the given command by searching it in the path environment variable
whileUsed to repeatedly execute a set of command as long as the COMMAND returns true
whoUsed to get information about currently logged in user on to system
whoamiDisplays the username of the current user when this command is invoked
writeAllows a user to communicate with other users, by copying lines from one user’s terminal to others

xargsUsed to build and execute commands from standard input. It converts input recieved from standard input into arguments of a command
xdg-openUsed to open a file or URL in the user’s preferred application

yesUsed to print a continous output stream of given STRING. If STRING is not mentioned then it prints ‘y’

zdiffUsed to invoke the diff program on files compressed via gzip
zdumpUsed to print the current time in the specified zone or you can say prints the current time in each zonename named on the command line
zgrepUsed to search out expressions from a given a file even if it is compressed
zipIt is a compression and file packaging utility for Unix. Each file is stored in single .zip {.zip-filename} file with the extension .zip

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