Brief overview of Unix and Linux commands

Updated: 07/12/2017 by Computer Hope

Below is a listing of each of the Unix and Linux commands currently listed on Computer Hope and a brief explanation of each command. Clicking on any of the commands will display additional help and information about that command.

Note: Not all the below commands will work with every distribution and may also not work because of your privileges.

Reference Guides
Regular Expressions Quick Reference Overview of using regular expressions in commands and searches
Command Description
a2p Create a Perl script from an AWK script.
ac Print statistics about user connection time.
addgroup Add a group to the system.
adduser Add a user to the system.
agrep Version of the grep utility which also matches approximate patterns.
alias Create an alternate name for a command.
apropos Search the manual pages for a keyword or regular expression.
apt-cache Search for information about software packages available through APT.
apt-get Command line tool for managing APT software packages.
aptitude Text-based front end for the APT package management system.
ar Create, modify, and extract files from archives.
arch Display the architecture of the system.
arp Manipulate the system ARP cache.
as An assembler.
aspell An interactive spell checker.
at Schedule a command to be run at a certain time.
awk Interpreter for the AWK text processing programming language.
basename Strip directory information and suffixes from file names.
bash The Bourne Again shell command interpreter.
bc A calculator.
bdiff Identify the differences between two very big files.
bfs An editor which can load very large files.
bg Resume a suspended program without bringing it to the foreground.
biff Receive detailed mail notifications at the command line.
break Break out of a while, for, foreach, or until loop.
bs A Linux version of the popular game "Battleship."
bye On some systems, an alias for the exit command.
cal Display a conveniently-formatted calendar from the command line.
calendar Display appointments and reminders.
cancel Cancel a print job under the System V operating system.
cat Output the contents of a file.
cc Compiler of the C programming language.
cd Change the working directory.
cfdisk A more user-friendly version of the fdisk disk partitioning utility.
chdir Function and alias for the cd command.
checkeq Language processor which assists in describing equations.
checknr Check nroff and troff files for errors.
chfn Change a user's finger information.
chgrp Change the group ownership of files and directories.
chkey Change the secure RPC key pair on SunOS.
chmod Change the permissions of files and directories.
chown Change the ownership of files and directories.
chroot Run a command or shell from another directory, and treat that directory as root.
chsh Change login shell.
cksum Calculate and display a CRC for files.
clear Clears the screen.
cmp Compare two files byte by byte.
col Filter reverse linefeeds.
comm Compare two sorted files line by line.
compress Compress a file or files.
continue Break out of a while, for, foreach, or until loop.
cp Copy files and directories.
cpio Copy files to or from archives.
crontab View and edit a list of jobs for the system to run at regular intervals.
csh The C shell command interpreter.
csplit Split files based on a defined context.
ctags Create tag files for source code.
cu Calls up another system, acting as a dial-in terminal.
curl Transfer data to or from a server.
cut Remove or "cut out" sections of each line of a file or files.
date Output the current date and time.
dc An arbitrary-precision arithmetic package.
dd Copy and convert the encoding of files.
delgroup Remove a group from the system.
deluser Remove a user from the system.
depmod Generate a list of kernel module dependences and associated map files.
deroff Remove nroff/troff, tbl, and eqn constructs from files.
df Report the amount of available disk space on file systems.
dhclient Communicate with a DHCP server to obtain a dynamic IP address.
diff Identify the differences between two files.
dig DNS lookup utility.
dircmp Compare the contents of two directories, listing unique files.
dirname Strip the file name from a pathname, leaving only the directory component.
dmesg Print or control the kernel ring buffer.
dos2unix Convert text files between DOS and Unix formats.
dpkg Query, install, remove, and maintain Debian software packages and their dependencies.
dpost Translate files created by troff into PostScript under Solaris.
du Report the amount of disk space used by a file or files.
echo Output text.
ed A simple text editor.
edit A text editor.
egrep Filter text which matches an extended regular expression.
eject Eject removable media.
elm A mail client.
emacs A highly extensible text editor.
enable Enable and disable LP printers.
env Report the value of environment variables.
eqn Language processor for describing equations.
ex Line-editor mode of the vi text editor.
exit Exit the command shell.
expand Expand tab characters to a series of spaces.
expr Evaluate arguments as an expression.
fc List, edit, or re-execute commands from the command history.
fdisk A disk partitioning utility.
fg Resumes a suspended job and brings it to the foreground.
fgrep Filter text which matches a fixed-character string.
file Determine a file's type.
find Find files within a directory hierarchy.
findsmb List information about machines networked with the Samba protocol.
finger List information about a user.
fmt A formatter for simplifying and optimizing text files.
fold Wrap lines of text to a specified line width.
for Execute a set of commands in a repeating loop.
foreach Execute a set of commands once for each of a given set of input items.
free  Display the amount of free and used memory.
fsck Check and repair a Linux file system.
ftp Conduct an interactive FTP session over a secure network connection.
fuser Identify processes using files or sockets.
gawk GNU's version of the AWK programming language.
getfacl Display file access control lists.
gpasswd Administer /etc/group and /etc/gshadow.
gprof Display call graph profile data.
grep Filter text which matches a regular expression.
groupadd Add a group to the system.
groupdel Remove a group from the system.
groupmod Modify a group definition.
gunzip Expand compressed files.
gview An alias which launches a graphical version of the vim text editor.
gvim An alias for vim.
gzip Create, modify, list the contents of, and extract files from GNU zip archives.
halt Stop the computer.
hash Access internal hash tables under Solaris.
hashstat Evaluate the effectiveness of internal hash tables under Solaris.
head Display the first lines of a file.
help Display help for built-in shell commands.
history Display the command history.
host Convert a host name to an IP address and vice versa.
hostid Print the numeric identifier for the current host.
hostname Set or print the hostname of system.
id Display real and effective user and group IDs.
ifconfig View or modify the configuration of network interfaces.
ifdown Disable a network interface.
ifquery Parse information about a network interface.
ifup Enable a network interface.
info Read Info documents.
init The parent of all processes on the system.
insmod Insert a module into the Linux kernel.
iostat Report CPU and I/O statistics for devices and partitions.
ip Display and manipulate information about routing, devices, policy routing and tunnels.
isalist Display the native instruction sets available on a Solaris system.
iwconfig Configure a wireless network interface.
jobs List the status of all running jobs.
join Join the lines of two files which share a common field of data.
keylogin Decrypt a user's secret key on SunOS.
kill Send a signal to a process, affecting its behavior or killing it.
killall Kill processes by name.
ksh The Korn shell command interpreter.
last Display a listing of the most recently logged-in users.
ld Link editor for object files.
ldd List dynamic dependencies of executable files or shared objects.
less Scrolling text viewer.
lex Generate programs for performing lexical tasks.
link Create a hard link to a regular file.
ln Create a link, or a symbolic link, to a file or directory.
lo Exit the command shell.
locate Search a local database to find files by name.
login Begin a session on a system.
logname Return a user's login name.
logout Exit the command shell.
losetup Set up and control loop devices.
lp Print a file on the System V operating system.
lpadmin Configure LP print services.
lpc Control line printers.
lpq List the status of available printers.
lpr Submit print requests.
lprm Remove requests from the print queue.
lpstat List the status of the LP print services.
ls List the contents of a directory or directories.
lsb_release Display information about your Linux distribution.
lsmod Show the status of Linux kernel modules.
lsof List open files.
lzcat View compressed .lzma files.
lzma Compress files to .lzma file.
mach Display the processor of the current system.
mail Read, compose, and manage mail.
mailcompat Provide SunOS 4.x compatibility for the Solaris mailbox format.
mailx Process mail messages.
make Automatically build executable programs and libraries from source code.
man Display the manual page of a given command.
md5sum Computes and checks the MD5 message digest.
merge Performs a merge of the contents of three files.
mesg Control if (non-root) users can send messages to your terminal.
mii-tool View and manipulate the status of a media-independent interface.
mkdir Create a directory.
mkfs Build a Linux file system, usually a hard disk partition.
mkswap Set up a Linux swap area.
modinfo Show information about a Linux kernel module.
modprobe Add and remove modules from the Linux kernel.
more Display text one screen at a time.
mount Mount a file system so that its data may be accessed.
mt Control magnetic tapes.
mv Move files and directories from one location to another, and optionally rename them.
myisamchk Check, repair, optimize, or fetch information about a MySQL database.
mysql An open-source relational database management system.
mysqldump A tool for backing up or transferring MySQL databases.
nc TCP/IP swiss army knife.
neqn Language processor for describing equations.
netstat Print information about network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.
newalias Install new elm aliases.
newform Change the format of a text file under Solaris.
newgrp Log into a new group.
nice Invoke a command with an altered scheduling priority.
niscat Display NIS+ tables and objects.
nischmod Change access rights on a NIS+ object.
nischown Change the owner of a NIS+ object on a system running Solaris.
nischttl Change the time to live value of a NIS+ object.
nisdefaults Display NIS+ default values.
nisgrep Utilities for searching NIS+ tables.
nismatch Utilities for searching NIS+ tables.
nispasswd Change NIS+ password information.
nistbladm Administer NIS+ tables.
nl Number the lines in a file.
nmap Network exploration tool and security port scanner.
nohup Instruct a command to continue running even if the session is disconnected or the user logs out.
nroff Format documents for terminal display or line-printer.
nslookup Query a name server for information about a remote host.
od Dump files in octal and other formats.
on Execute a command on a remote system, but with the local environment.
onintr Built-in shell function which responds to hardware interrupts.
optisa Determine which instruction set is optimal to use on a Solaris system.
pack Compress files using a Huffman algorithm.
pagesize Display the size of a page of memory in bytes.
parted A disk partition manipulation program.
partprobe Inform the operating system about changes to the partition table.
passwd Change a user's password.
paste Merge corresponding lines of files.
pax Read and write file archives, and copy directory hierarchies.
pcat Print the uncompressed contents of a compressed file.
perl Interpreter for the Perl programming language.
pg Browse page by page through text files.
pgrep Look up processes based on the name or other attributes.
pico A simple text editor.
pine A client for using mail and newsgroups.
ping Send ICMP ECHO_REQUEST packets to network hosts.
pkill Send a signal to any process whose attributes match a regular expression.
poweroff Stop the computer.
pr Format a text file for printing.
printenv Print all or part of the environment.
printf Write formatted output.
priocntl Display or set scheduling parameters of a processes under Solaris.
ps Report the status of a process or processes.
pstree Display processes in a tree format.
pvs Display the internal version information of dynamic objects within an ELF file.
pwd Print the name of the working directory.
quit Exit the command shell.
rcp Copy files to or from a remote system.
readlink Print the value of a symbolic link or canonical file name.
reboot Stop the computer.
red Run ed in "restricted" (less powerful, more secure) mode.
rehash Recompute internal hash tables under Solaris.
rename Rename multiple files according to a regular expression.
renice Alter the priority of running processes.
repeat Execute a set of commands in a repeating loop.
replace A string-replacement utility.
rgview An alias for vim.
rgvim An alias for vim.
rlogin Begin a session on a remote system.
rm Delete files.
rmdir Remove a directory.
rmmod Remove a module from the Linux kernel.
rn A newsgroup reader.
route Display and manipulate the IP routing table.
rpcinfo Report information about Remote Procedure Calls.
rsh Execute a command on a remote shell.
rsync A fast and versatile file copying tool capable of synchronizing files across remote systems.
rview An alias for vim.
rvim An alias for vim.
s2p Convert a sed script into a Perl script.
sag Under Solaris, Graphically displays system activity data generated by sar.
sar Display CPU activity under Solaris.
scp Copy files securely over a network connection.
screen Screen manager with VT100/ANSI terminal emulation.
script Record everything printed on your screen.
sdiff Compare two files, side-by-side.
sed A utility for filtering and transforming text.
sendmail Send mail.
service Run a System V init script.
set Set the value of an environment variable.
setenv Set the value of an environment variable.
setfacl Modify the access control list of a file or files.
sfdisk A low-level disk partitioning program.
sftp Conduct an interactive FTP session over a secure network connection.
sh The Bourne shell command interpreter.
sha224sum Computes and checks a SHA224 message digest.
sha256sum Computes and checks a SHA256 message digest.
sha384sum Computes and checks a SHA384 message digest.
sha512sum Computes and checks a SHA512 message digest.
shred Overwrite a file's contents, irrevocably destroying them.
shutdown Schedule a time for the system to be powered down.
sleep Wait a given number of seconds.
slogin Login to a remote system securely.
smbclient An ftp-like client for accessing SMB/CIFS resources on servers.
sort Sort the lines in a text file.
spell A spell checker.
split Split a file into pieces.
startx Start an X Window System session.
stat Display the status of a file or filesystem.
stop Stop a running job.
strftime Format strings that represent the system date and time.
strip Discard symbols from object files.
stty Set options for your terminal display.
su Become the superuser or another user.
sudo Execute a command as the superuser.
swapoff Disable a Linux swap area.
swapon Enable a Linux swap area.
sysklogd Linux system logging utilities.
tabs Set tab stops on a terminal.
tac Output the contents of files in reverse order.
tail Print the last lines of a text file.
talk Talk with other logged in users.
tar Create, modify, list the contents of, and extract files from tar archives.
tbl Preprocessor which formats tables for nroff or troff.
tcopy Copy a magnetic tape.
tcpdump Capture raw network traffic.
tcsh A command-line shell similar to csh, with some additional features.
tee Route a file's contents to multiple outputs.
telinit Process control initialization.
telnet Connect to a remote system using the telnet protocol.
test Check file types and compare values.
time Report how long it takes for a command to execute.
timex Report process data and system activity for a specified command.
todos Convert text files between DOS and Unix formats.
top Display a sortable, continually-updated list of processes.
touch Update the timestamp of a file or directory.
tput Initialize a terminal or query the terminfo database.
tr Translate one set of characters to another.
traceroute Trace the route that packets take to a remote host.
trap A function which "traps" signals and interrupts, and reacts to them.
tree List the contents of a file hierarchy visually in a tree format.
troff Typeset or format documents for terminal display or line-printer.
tty Print the file name of the terminal connected to standard input.
ul Translate underscores to underlining.
umask Get or set the file mode creation mask.
umount Unmount a file system, making its data inaccessible.
unalias Remove an alias.
uname Print information about the current system.
uncompress Extract files from compressed archives.
unhash Remove internal hash table under Solaris.
uniq Identify, and optionally filter out, repeated lines in a file.
unlink Remove a file.
unlzma Decompress .lzma files.
unpack Expand a compressed file.
until Execute a set of commands until a certain condition is true.
unxz Decompress .xz files.
unzip List, test and extract compressed files in a zip archive.
uptime Display information about how long the system has been running.
useradd Add a user to the system.
userdel Remove a user from the system.
usermod Modify a user's account.
vacation Reply to mail automatically.
vgrind "Grind" nice program listings.
vi Text editor based on the visual mode of ex.
view Run vim in read-only mode.
vim An advanced version of vi.
vipw Safely edit the password file.
visudo Safely edit the sudoers file.
vmstat Report statistics about virtual memory usage.
w Show who is logged on and what they are doing.
wait Await process completion.
wall Send a message to all logged-in users.
wc Display a count of lines, words, and characters in a file.
wget Download files via HTTP or FTP.
whatis Display short manual page descriptions.
whereis Locate the binary, source, and manual page files for a command.
which Locate the binary executable of a command.
while Execute a set of actions while a certain condition is true.
who Report which users are logged in to the system.
whoami Print your effective userid.
whois An internet user name directory service.
write Send a message to another user.
X Executable of the X Window System.
Xorg The executable of the X Window System server.
xargs Build and execute complex commands, and execute them on multiple files.
xfd Display all the characters in an X font.
xhost Server access control program for X.
xinit The initializer of the X Window System.
xlsfonts Display X font lists.
xrdb An X server resource database utility.
xset A user preference utility for X.
xterm A terminal emulator for X.
xz Compress files to .xz files.
xzcat View compressed .xz files.
yacc "Yet another compiler-compiler."
yes Repeatedly output a given string, or the letter "y".
yppasswd Change a network password in an NIS database.
yum An interactive rpm-based package manager.
zcat Print the uncompressed contents of compressed files.
zip A compression and archiving utility.
zipcloak Encrypt files within an existing zip archive.
zipinfo Display technical information about a zip file.
zipnote View, add, or modify a zip file's comments.
zipsplit Split a single zip archive into a set of smaller zip files.

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