Linux Command Line Reference

#A

accept   Accept or Reject jobs to a destination, such as a printer.

access   Check a user’s RWX permission for a file.

aclocal   GNU autoconf too

aconnect    ALSA sequencer connection manager.

acpi   Show information about the Advanced Configuration and Power Interface.

acpi_available   Check if ACPI functionality exists on the system.

acpid   Informs user-space programs about ACPI events.

addr2line   Used to convert addresses into file names and line numbers.

addresses   Formats for internet mail addresses.

agetty   An alternative Linux Getty

alias   Create an alias for Linux commands

alsactl   Access advanced controls for ALSA soundcard driver.

amidi   Perform read/write operation for ALSA RawMIDI ports.

amixer   Access CLI-based mixer for ALSA soundcard driver.

anacron   Used to run commands periodically.

aplay   Sound recorder and player for CLI.

aplaymidi   CLI utility used to play MIDI files.

apm   Show Advanced Power Management (APM) hardware info on older systems.

apmd   Used to handle events reported by APM BIOS drivers.

apropos   Shows the list of all man pages containing a specific keyword

apt   Advanced Package Tool, a package management system for Debian and derivatives.

apt-get   Command-line utility to install/remove/update packages based on APT system.

aptitude   Another utility to add/remove/upgrade packages based on the APT system.

ar   A utility to create/modify/extract from archives.

arch   Display print machine hardware name.

arecord   Just like aplay, it’s a sound recorder and player for ALSA soundcard driver.

arecordmidi   Record standard MIDI files.

arp   Used to make changes to the system’s ARP cache

as   A portable GNU assembler.

aspell   An interactive spell checker utility.

at   Used to schedule command execution at specified date & time, reading commands from an input file.

atd   Used to execute jobs queued by the at command.

atq   List a user’s pending jobs for the at command.

atrm   Delete jobs queued by the at command.

audiosend   Used to send an audio recording as an email.

aumix   An audio mixer utility.

autoconf   Generate configuration scripts from a TEMPLATE-FILE and send the output to standard output.

autoheader   Create a template header for configure.

automake   Creates GNU standards-compliant Makefiles from template files

autoreconf   Update generated configuration files.

autoscan   Generate a preliminary configure.in

autoupdate   Update a configure.in file to newer autoconf.

awk   Used to find and replace text in a file(s).

#B

badblocks   Search a disk partition for bad sectors.

banner   Used to print characters as a poster.

basename   Used to display filenames with directoy or suffix.

bash   GNU Bourne-Again Shell.

batch   Used to run commands entered on a standard input.

bc   Access the GNU bc calculator utility.

bg   Send processes to the background.

biff   Notify about incoming mail and sender’s name on a system running comsat server.

bind   Used to attach a name to a socket.

bison   A GNU parser generator, compatible with yacc.

break   Used to exit from a loop (eg: for, while, select).

builtin   Used to run shell builtin commands, make custom functions for commands extending their functionality.

bzcmp   Used to call the cmp program for bzip2 compressed files.

bzdiff   Used to call the diff program for bzip2 compressed files.

bzgrep   Used to call grep for bzip2 compressed files.

bzip2   A block-sorting file compressor used to shrink given files.

bzless   Used to apply ‘less’ (show info one page at a time) to bzip2 compressed files.

bzmore   Used to apply ‘more’ (an inferior version of less) to bzip2 compressed files.

#C

cal   Show calendar.

cardctl   Used to control PCMCIA sockets and select configuration schemes.

cardmgr   Keeps an eye on the added/removes sockets for PCMCIA devices.

case   Execute a command conditionally by matching a pattern.

cat   Used to concatenate files and print them on the screen.

cc   GNU C and C++ compiler.

cd   Used to change directory.

cdda2wav   Used to rip a CD-ROM and make WAV file.

cdparanoia   Record audio from CD more reliably using data-verification algorithms.

cdrdao   Used to write all the content specified to a file to a CD all at once.

cdrecord   Used to record data or audio compact discs.

cfdisk   Show or change the disk partition table.

chage   Used to change user password information.

chattr   Used to change file attributes.

chdir   Used to change active working directory.

chfn   Used to change real user name and information.

chgrp   Used to change group ownership for file.

chkconfig   Manage execution of runlevel services.

chmod   Change access permission for a file(s).

chown   Change the owner or group for a file.

chpasswd   Update password in a batch.

chroot   Run a command with root privileges.

chrt   Alter process attributed in real-time.

chsh   Switch login shell.

chvt   Change foreground virtual terminal.

cksum   Perform a CRC checksum for files.

clear   Used to clear the terminal window.

cmp   Compare two files (byte by byte).

col   Filter reverse (and half-reverse) line feeds from the input.

colcrt   Filter nroff output for CRT previewing.

colrm   Remove columns from the lines of a file.

column   A utility that formats its input into columns.

comm   Used to compare two sorted files line by line.

command   Used to execute a command with arguments ignoring shell function named command.

compress   Used to compress one or more file(s) and replacing the originals ones.

continue   Resume the next iteration of a loop.

cp   Copy contents of one file to another.

cpio   Copy files from and to archives.

cpp   GNU C language processor.

cron   A daemon to execute scheduled commands.

crond   Same work as cron.

crontab   Manage crontab files (containing schedules commands) for users.

csplit   Split a file into sections on the basis of context lines.

ctags   Make a list of functions and macro names defined in a programming source file.

cupsd   A scheduler for CUPS.

curl   Used to transfer data from or to a server using supported protocols.

cut   Used to remove sections from each line of a file(s).

cvs   Concurrent Versions System. Used to track file versions, allow storage/retrieval of previous versions, and enables multiple users to work on the same file.

#D

date   Show system date and time.

dc   Desk calculator utility.

dd   Used to convert and copy a file, create disk clone, write disk headers, etc.

ddrescue   Used to recover data from a crashed partition.

deallocvt   Deallocates kernel memory for unused virtual consoles.

debugfs   File system debugger for ext2/ext3/ext4

declare   Used to declare variables and assign attributes.

depmod   Generate modules.dep and map files.

devdump   Interactively displays the contents of device or file system ISO.

df   Show disk usage.

diff   Used to compare files line by line.

diff3   Compare three files line by line.

dig   Domain Information Groper, a DNS lookup utility.

dir   List the contents of a directory.

dircolors   Set colors for ‘ls’ by altering the LS_COLORS environment variable.

dirname   Display pathname after removing the last slash and characters thereafter.

dirs   Show the list of remembered directories.

disable   Restrict access to a printer.

dlpsh   Interactive Desktop Link Protocol (DLP) shell for PalmOS.

dmesg   Examine and control the kernel ring buffer.

dnsdomainname   Show the DNS domain name of the system.

dnssec-keygen   Generate encrypted Secure DNS keys for a given domain name.

dnssec-makekeyset   Produce domain key set from one or more DNS security keys generated by dnssec-keygen.

dnssec-signkey   Sign a secure DNS keyset with key signatures specified in the list of key-identifiers.

dnssec-signzone   Sign a secure DNS zonefile with the signatures in the specified list of key-identifiers.

doexec   Used to run an executable with an arbitrary argv list provided.

domainname   Show or set the name of current NIS (Network Information Services) domain.

dosfsck   Check and repair MS-DOS file systems.

du   Show disk usage summary for a file(s).

dump   Backup utility for ext2/ext3 file systems.

dumpe2fs   Dump ext2/ext3/ext4 file systems.

dumpkeys   Show information about the keyboard driver’s current translation tables.

#E

e2fsck   Used to check ext2/ext3/ext4 file systems.

e2image   Store important ext2/ext3/ext4 filesystem metadata to a file.

e2label   Show or change the label on an ext2/ext3/ext4 filesystem.

echo   Send input string(s) to standard output i.e. display text on the screen.

ed   GNU Ed – a line-oriented text editor.

edquota   Used to edit filesystem quotas using a text editor, such as vi.

egrep   Search and display text matching a pattern.

eject   Eject removable media.

elvtune   Used to set latency in the elevator algorithm used to schedule I/O activities for specified block devices.

emacs   Emacs text editor command line utility.

enable   Used to enable/disable shell builtin commands.

env   Run a command in a modified environment. Show/set/delete environment variables.

envsubst   Substitute environment variable values in shell format strings.

esd   Start the Enlightenment Sound Daemon (EsounD or esd). Enables multiple applications to access the same audio device simultaneously.

esd-config   Manage EsounD configuration.

esdcat   Use EsounD to send audio data from a specified file.

esdctl   EsounD control program.

esddsp   Used to reroute non-esd audio data to esd and control all the audio using esd.

esdmon   Used to copy the sound being sent to a device. Also, send it to a secondary device.

esdplay   Use EsounD system to play a file.

esdrec   Use EsounD to record audio to a specified file.

esdsample   Sample audio using esd.

etags   Used to create a list of functions and macros from a programming source file. These etags are used by emacs. For vi, use ctags.

ethtool   Used to query and control network driver and hardware settings.

eval   Used to evaluate multiple commands or arguments are once.

ex   Interactive command

exec   An interactive line-based text editor.

exit   Exit from the terminal.

expand   Convert tabs into spaces in a given file and show the output.

expect   An extension to the Tcl script, it’s used to automate interaction with other applications based on their expected output.

export   Used to set an environment variable.

expr   Evaluate expressions and display them on standard output.

#F

factor   Display prime factors of specified integer numbers.

false   Do nothing, unsuccessfully. Exit with a status code indicating failure.

fc-cache   Make font information cache after scanning the directories.

fc-list   Show the list of available fonts.

fdformat   Do a low-level format on a floppy disk.

fdisk   Make changes to the disk partition table.

fetchmail   Fetch mail from mail servers and forward it to the local mail delivery system.

fg   Used to send a job to the foreground.

fgconsole   Display the number of the current virtual console.

fgrep   Display lines from a file(s) that match a specified string. A variant of grep.

file   Determine file type for a file.

find   Do a file search in a directory hierarchy.

finger   Display user data including the information listed in .plan and .project in each user’s home directory.

fingerd   Provides a network interface for the finger program.

flex   Generate programs that perform pattern-matching on text.

fmt   Used to convert text to a specified width by filling lines and removing new lines, displaying the output.

fold   Wrap input line to fit in a specified width.

for   Expand words and run commands for each one in the resultant list.

formail   Used to filter standard input into mailbox format.

format   Used to format disks.

free   Show free and used system memory.

fsck   Check and repair a Linux file system

ftp   File transfer protocol user interface.

ftpd   FTP server process.

function   Used to define function macros.

fuser   Find and kill a process accessing a file.

#G

g++   Run the g++ compiler.

gawk   Used for pattern scanning and language processing. A GNU implementation of AWK language.

gcc   A C and C++ compiler by GNU.

gdb   A utility to debug programs and know about where it crashes.

getent   Shows entries from Name Service Switch Libraries for specified keys.

getkeycodes   Displays the kernel scancode-to-keycode mapping table.

getopts   A utility to parse positional parameters.

gpasswd   Allows an administrator to change group passwords.

gpg   Enables encryption and signing services as per the OpenPGP standard.

gpgsplit   Used to split an OpenPGP message into packets.

gpgv   Used to verify OpenPGP signatures.

gpm   It enables cut and paste functionality and a mouse server for the Linux console.

gprof   Shows call graph profile data.

grep   Searches input files for a given pattern and displays the relevant lines.

groff   Serves as the front-end of the groff document formatting system.

groffer   Displays groff files and man pages.

groupadd   Used to add a new user group.

groupdel   Used to remove a user group.

groupmod   Used to modify a group definition.

groups   Show the group(s) to which a user belongs.

grpck   Verifies the integrity of group files.

grpconv   Creates a gshadow file from a group or an already existing gshadow.

gs   Invokes Ghostscript, and interpreter and previewer for Adobe’s PostScript and PDF languages.

gunzip   A utility to compress/expand files.

gzexe   Used compress executable files in place and have them automatically uncompress and run at a later stage.

gzip   Same as gzip.

#H

halt   Command used to half the machine.

hash   Shows the path for the commands executed in the shell.

hdparm   Show/configure parameters for SATA/IDE devices.

head   Shows first 10 lines from each specified file.

help   Display’s help for a built-in command.

hexdump   Shows specified file output in hexadecimal, octal, decimal, or ASCII format.

history   Shows the command history.

host   A utility to perform DNS lookups.

hostid   Shows host’s numeric ID in hexadecimal format.

hostname   Display/set the hostname of the system.

htdigest   Manage the user authentication file used by the Apache web server.

htop   An interactive process viewer for the command line.

hwclock   Show or configure the system’s hardware clock.

#I

iconv   Convert text file from one encoding to another.

id   Show user and group information for a specified user.

if   Execute a command conditionally.

ifconfig   Used to configure network interfaces.

ifdown   Stops a network interface.

ifup   Starts a network interface.

imapd   An IMAP (Interactive Mail Access Protocol) server daemon.

import   Capture an X server screen and saves it as an image.

inetd   Extended internet services daemon, it starts the programs that provide internet services.

info   Used to read the documentation in Info format.

init   Systemd system and service manager.

insmod   A program that inserts a module into the Linux kernel.

install   Used to copy files to specified locations and set attributions during the install process.

iostat   Shows statistics for CPU, I/O devices, partitions, network filesystems.

ip   Display/manipulate routing, devices, policy, routing and tunnels.

ipcrm   Used to remove System V interprocess communication (IPC) objects and associated data structures.

ipcs   Show information on IPC facilities for which calling process has read access.

iptables   Administration tool for IPv4 packet filtering and NAT.

iptables-restore   Used to restore IP tables from data specified in the input or a file.

iptables-save   Used to dump IP table contents to standard output.

isodump   A utility that shows the content iso9660 images to verify the integrity of directory contents.

isoinfo   A utility to perform directory like listings of iso9660 images.

isosize   Show the length of an iso9660 filesystem contained in a specified file.

isovfy   Verifies the integrity of an iso9660 image.

ispell   A CLI-based spell-check utility.

#J

jobs   Show the list of active jobs and their status.

join   For each pair of input lines, join them using a command field and display on standard output.

#K

kbd_mode   Set a keyboard mode. Without arguments, shows the current keyboard mode.

kbdrate   Reset keyboard repeat rate and delay time.

kill   Send a kill (termination) signal to one more processes.

killall   Kills a process(es) running a specified command.

killall5   A SystemV killall command. Kills all the processes excluding the ones which it depends on.

klogd   Control and prioritize the kernel messages to be displayed on the console, and log them through syslogd.

kudzu   Used to detect new and enhanced hardware by comparing it with existing database. Only for RHEL and derivates.

#L

last   Shows a list of recent logins on the system by fetching data from /var/log/wtmp file.

lastb   Shows the list of bad login attempts by fetching data from /var/log/btmp file.

lastlog   Displays information about the most recent login of all users or a specified user.

ld   The Unix linker, it combines archives and object files. It then puts them into one output file, resolving external references.

ldconfig   Configure dynamic linker run-time bindings.

ldd   Shows shared object dependencies.

less   Displays contents of a file one page at a time. It’s advanced than more command.

lesskey   Used to specify key bindings for less command.

let   Used to perform integer artithmetic on shell variables.

lftp   An FTP utility with extra features.

lftpget   Uses lftop to retrieve HTTP, FTP, and other protocol URLs supported by lftp.

link   Create links between two files. Similar to ln command.

ln   Create links between files. Links can be hard (two names for the same file) or soft (a shortcut of the first file).

loadkeys   Load keyboard translation tables.

local   Used to create function variables.

locale   Shows information about current or all locales.

locate   Used to find files by their name.

lockfile   Create semaphore file(s) which can be used to limit access to a file.

logger   Make entries in the system log.

login   Create a new session on the system.

logname   Shows the login name of the current user.

logout   Performs the logout operation by making changes to the utmp and wtmp files.

logrotate   Used for automatic rotation, compression, removal, and mailing of system log files.

look   Shows any lines in a file containing a given string in the beginning.

losetup   Set up and control loop devices.

lpadmin   Used to configure printer and class queues provided by CUPS (Common UNIX Printing System).

lpc   Line printer control program, it provides limited control over CUPS printer and class queues.

lpinfo   Shows the list of avaiable devices and drivers known to the CUPS server.

lpmove   Move on or more printing jobs to a new destination.

lpq   Shows current print queue status for a specified printer.

lpr   Used to submit files for printing.

lprint   Used to print a file.

lprintd   Used to abort a print job.

lprintq   List the print queue.

lprm   Cancel print jobs.

lpstat   Displays status information about current classes, jobs, and printers.

ls   Shows the list of files in the current directory.

lsattr   Shows file attributes on a Linux ext2 file system.

lsblk   Lists information about all available or the specified block devices.

lsmod   Show the status of modules in the Linux kernel.

lsof   List open files.

lspci   List all PCI devices.

lsusb   List USB devices.

#M

m4   Macro processor.

mail   Utility to compose, receive, send, forward, and reply to emails.

mailq   Shows to list all emails queued for delivery (sendmail queue).

mailstats   Shows current mail statistics.

mailto   Used to send mail with multimedia content in MIME format.

make   Utility to maintain groups of programs, recompile them if needed.

makedbm   Creates an NIS (Network Information Services) database map.

makemap   Creates database maps used by the keyed map lookups in sendmail.

man   Shows manual pages for Linux commands.

manpath   Determine search path for manual pages.

mattrib   Used to change MS-DOS file attribute flags.

mbadblocks   Checks MD-DOS filesystems for bad blocks.

mcat   Dump raw disk image.

mcd   Used to change MS-DOS directory.

mcopy   Used to copy MS-DOS files from or to Unix.

md5sum   Used to check MD5 checksum for a file.

mdel, mdeltree   Used to delete MS-DOS file. mdeltree recursively deletes MS-DOS directory and its contents.

mdir   Used to display an MS-DOS directory.

mdu   Used to display the amount of space occupied by an MS-DOS directory.

merge   Three-way file merge. Includes all changes from file2 and file3 to file1.

mesg   Allow/disallow osends to sedn write messages to your terminal.

metamail   For sending and showing rich text or multimedia email using MIME typing metadata.

metasend    An interface for sending non-text mail.

mformat   Used to add an MS-DOS filesystem to a low-level formatted floppy disk.

mimencode   Translate to/from MIME multimedia mail encoding formats.

minfo   Display parameters of an MS-DOS filesystem.

mkdir   Used to create directories.

mkdosfs   Used to create an MS-DOS filesystem under Linux.

mke2fs   Used create an ext2/ext3/ext4 filesystem.

mkfifo   Used to create named pipes (FIFOs) with the given names.

mkfs   Used to build a Linux filesystem on a hard disk partition.

mkfs.ext3   Same as mke2fs, create an ext3 Linux filesystem.

mkisofs   Used to create an ISO9660/JOLIET/HFS hybrid filesystem.

mklost+found   Create a lost+found directory on a mounted ext2 filesystem.

mkmanifest   Makes a list of file names and their DOS 8.3 equivalent.

mknod   Create a FIFO, block (buffered) special file, character (unbuffered) special file with the specified name.

mkraid   Used to setup RAID device arrays.

mkswap   Set up a Linux swap area.

mktemp   Create a temporary file or directory.

mlabel   Make an MD-DOS volume label.

mmd   Make an MS-DOS subdirectory.

mmount   Mount an MS-DOS disk.

mmove   Move or rename an MS-DOS file or subdirectory.

mmv   Mass move and rename files.

modinfo   Show information about a Linux kernel module.

modprobe   Add or remove modules from the Linux kernel.

more   Display content of a file page-by-page.

most   Browse or page through a text file.

mount   Mount a filesystem.

mountd   NFS mount daemon.

mpartition   Partition an MS-DOS disk.

mpg123   Command-line mp3 player.

mpg321   Similar to mpg123.

mrd   Remove an MS-DOS subdirectory.

mren   Rename an existing MS-DOS file.

mshowfat   Show FTA clusters allocated to a file.

mt   Control magnetic tape drive operation.

mtools   Utilities to access MS-DOS disks.

mtoolstest   Tests and displays the mtools configuration files.

mtr   A network diagnostic tool.

mtype   Display contents of an MS-DOS file.

mv   Move/rename files or directories.

mzip   Change protection mode and eject disk on Zip/Jaz drive.

#N

named   Internet domain name server.

namei   Follow a pathname until a terminal point is found.

nameif   Name network interfaces based on MAC addresses.

nc   Netcat utility. Arbitrary TCP and UDP connections and listens.

netstat   Show network information.

newaliases   Rebuilds mail alias database.

newgrp   Log-in to a new group.

newusers   Update/create new users in batch.

nfsd   Special filesystem for controlling Linux NFS server.

nfsstat   List NFS statistics.

nice   Run a program with modified scheduling priority.

nl   Show numbered line while displaying the contents of a file.

nm   List symbols from object files.

nohup   Run a command immune to hangups.

notify-send   A program to send desktop notifications.

nslookup   Used performs DNS queries. Read this article for more info.

nsupdate   Dynamic DNS update utility.

#O

objcopy   Copy and translate object files.

objdump   Display information from object files.

od   Dump files in octal and other formats.

op   Operator access, allows system administrators to grant users access to certain root operations that require superuser privileges.

open   Open a file using its default application.

openvt   Start a program on a new virtual terminal (VT).

#P

passwd   Change user password.

paste   Merge lines of files. Write to standard output, TAB-separated lines consisting of sqentially correspnding lines from each file.

patch   Apply a patchfile (containing differences listing by diff program) to an original file.

pathchk   Check if file names are valid or portable.

perl   Perl 5 language interpreter.

pgrep   List process IDs matching the specified criteria among all the running processes.

pidof   Find process ID of a running program.

ping   Send ICMP ECHO_REQUEST to network hosts.

pinky   Lightweight finger.

pkill   Send kill signal to processes based on name and other attributes.

pmap   Report memory map of a process.

popd   Removes directory on the head of the directory stack and takes you to the new directory on the head.

portmap   Converts RPC program numbers to IP port numbers.

poweroff   Shuts down the machine.

pppd   Point-to-point protocol daemon.

pr   Convert (column or paginate) text files for printing.

praliases   Prints the current system mail aliases.

printcap   Printer capability database.

printenv   Show values of all or specified environment variables.

printf   Show arguments formatted according to a specified format.

ps   Report a snapshot of the current processes.

ptx   Produce a permuted index of file contents.

pushd   Appends a given directory name to the head of the stack and then cd to the given directory.

pv   Monitor progress of data through a pipe.

pwck   Verify integrity of password files.

pwconv   Creates shadow from passwd and an optionally existing shadow.

pwd   Show current directory.

python

#Q

quota   Shows disk usage, and space limits for a user or group. Without arguments, only shows user quotas.

quotacheck   Used to scan a file system for disk usage.

quotactl   Make changes to disk quotas.

quotaoff   Enable enforcement of filesystem quotas.

quotaon   Disable enforcement of filesystem quotas.

quotastats   Shows the report of quota system statistics gathered from the kernel.

#R

raidstart   Start/stop RAID devices.

ram   RAM disk device used to access the RAM disk in raw mode.

ramsize   Show usage information for the RAM disk.

ranlib   Generate index to the contents of an archive and store it in the archive.

rar   Create and manage RAR file in Linux.

rarpd   Respond to Reverse Address Resoultion Protocol (RARP) requests.

rcp   Remote copy command to copy files between remote computers.

rdate   Set system date and time by fetching information from a remote machine.

rdev   Set or query RAM disk size, image root device, or video mode.

rdist   Remote file distribution client, maintains identical file copies over multiple hosts.

rdistd   Start the rdist server.

read   Read from a file descriptor.

readarray   Read lines from a file into an array variable.

readcd   Read/write compact disks.

readelf   Shows information about ELF (Executable and Linkable fomrat) files.

readlink   Display value of a symbolic link or canonical file name.

readonly   Mark functions and variables as read-only.

reboot   Restart the machine.

reject   Accept/reject print jobs sent to a specified destination.

remsync   Synchronize remote files over email.

rename   Rename one or more files.

renice   Change priority of active processes.

repquota   Report disk usage and quotas for a specified filesystem.

reset   Reinitialize the terminal.

resize2fs   Used to resize ext2/ext3/ext4 file systems.

restore   Restore files from a backup created using dump.

return   Exit a shell function.

rev   Show contents of a file, reversing the order of characters in every line.

rexec   Remote execution client for exec server.

rexecd   Remote execution server.

richtext   View “richtext” on an ACSII terminal.

rlogin   Used to connect a local host system with a remote host.

rlogind   Acts as the server for rlogin. It facilitates remote login, and authentication based on privileged port numbers from trusted hosts.

rm   Removes specified files and directories (not by default).

rmail   Handle remote mail received via uucp.

rmdir   Used to remove empty directories.

rmmod   A program to remove modules from Linux kernel.

rndc   Name server control utility. Send command to a BIND DNS server over a TCP connection.

rootflags   Show/set flags for the kernel image.

route   Show/change IP routing table.

routed   A daemon, invoked at boot time, to manage internet routing tables.

rpcgen   An RPC protocol compiler. Parse a file written in the RPC language.

rpcinfo   Shows RPC information. Makes an RPC call to an RPC server and reports the findings.

rpm   A package manager for linux distributions. Originally developed for RedHat Linux.

rsh   Remote shell. Connects to a specified host and executes commands.

rshd   A daemon that acts as a server for rsh and rcp commands.

rsync   A versitile to for copying files remotely and locally.

runlevel   Shows previous and current SysV runlevel.

rup   Remote status display. Shows current system status for all or specified hosts on the local network.

ruptime   Shows uptime and login details of the machines on the local network.

rusers   Shows the list of the users logged-in to the host or on all machines on the local network.

rusersd   The rsuerd daemon acts as a server that responds to the queries from rsuers command.

rwall   Sends messages to all users on the local network.

rwho   Reports who is logged-in to the hosts on the local network.

rwhod   Acts as a server for rwho and ruptime commands.

#S

sane-find-scanner   Find SCSI and USB scanner and determine their device files.

scanadf   Retrieve multiple images from a scanner equipped with an automatic document feeder (ADF).

scanimage   Read images from image aquistion devices (scanner or camera) and display on standard output in PNM (Portable aNyMap) format.

scp   Copy files between hosts on a network securely using SSH.

screen   A window manager that enables multiple pseudo-terminals with the help of ANSI/VT100 terminal emulation.

script   Used to make a typescript of everything displayed on the screen during a terminal session.

sdiff   Shows two files side-by-side and highlights the differences.

sed   Stream editor for filtering and transforming text (from a file or a pipe input).

select   Synchronous I/O multiplexing.

sendmail   It’s a mail router or an MTA (Mail Transfer Agent). sendmail support can send a mail to one or more recepients using necessary protocols.

sensors   Shows the current readings of all sensor chips.

seq   Displays an incremental sequence of numbers from first to last.

set   Used to manipulate shell variables and functions.

setfdprm   Sets floppy disk parameters as provided by the user.

setkeycodes   Load kernel scancode-to-keycode mapping table entries.

setleds   Show/change LED light settings of the keyboard.

setmetamode   Define keyboard meta key handling. Without arguments, shows current meta key mode.

setquota   Set disk quotas for users and groups.

setsid   Run a program in a new session.

setterm   Set terminal attributes.

sftp   Secure File Transfer program.

sh   Command interpreter (shell) utility.

sha1sum   Compute and check 160-bit SHA1 checksum to verify file integrity.

shift   Shift positional parameters.

shopt   Shell options.

showkey   Examines codes sent by the keyboard displays them in printable form.

showmount   Shows information about NFS server mount on the host.

shred   Overwrite a file to hide its content (optionally delete it), making it harder to recover it.

shutdown   Power-off the machine.

size   Lists section size and the total size of a specified file.

skill   Send a signal to processes.

slabtop   Show kernel slab cache information in real-time.

slattach   Attack a network interface to a serial line.

sleep   Suspend execution for a specified amount of time (in seconds).

slocate   Display matches by searching filename databases. Takes ownership and file permission into consideration.

snice   Reset priority for processes.

sort   Sort lines of text files.

source   Run commands from a specified file.

split   Split a file into pieces of fixed size.

ss   Display socket statistics, similar to netstat.

ssh   An SSH client for logging in to a remote machine. It provides encrypted communication between the hosts.

ssh-add   Adds private key identities to the authentication agent.

ssh-agent   It holds private keys used for public key authentication.

ssh-keygen   It generates, manages, converts authentication keys for ssh.

ssh-keyscan   Gather ssh public keys.

sshd   Server for the ssh program.

stat   Display file or filesystem status.

statd   A daemon that listens for reboot notifications from other hosts, and manages the list of hosts to be notified when the local system reboots.

strace   Trace system calls and signals.

strfile   Create a random access file for storing strings.

strings   Search a specified file and prints any printable strings with at least four characters and followed by an unprintable character.

strip   Discard symbols from object files.

stty   Change and print terminal line settings.

su   Change user ID or become superuser.

sudo   Execute a command as superuser.

sum   Checksum and count the block in a file.

suspend   Suspend the execution of the current shell.

swapoff   Disable devices for paging and swapping.

swapon   Enable devices for paging and swapping.

symlink   Create a symbolic link to a file.

sync   Synchronize cached writes to persistent storage.

sysctl   Configure kernel parameters at runtime.

sysklogd   Linux system logging utilities. Provides syslogd and klogd functionalities.

syslogd   Read and log system messages to the system console and log files.

#T

tac   Concatenate and print files in reverse order. Opposite of cat command.

tail   Show the last 10 lines of each specified file(s).

tailf   Follow the growth of a log file. (Deprecated command)

talk   A two-way screen-oriented communication utility that allows two user to exchange messages simulateneously.

talkd   A remote user communication server for talk.

tar   GNU version of the tar archiving utility. Used to store and extract multiple files from a single archive.

taskset   Set/retrieve a process’s CPU affinity.

tcpd   Access control utility for internet services.

tcpdump   Dump traffic on network. Displays a description of the contents of packets on a network interface that match the boolean expression.

tcpslice   Extract pieces of tcpdump files or merge them.

tee   Read from standard input and write to standard output and files.

telinit   Change SysV runlevel.

telnet   Telnet protocol user interface. Used to interact with another host using telnet.

telnetd   A server for the telnet protocol.

test   Check file type and compare values.

tftp   User interface to the internet TFTP (Trivial File Transfer Protocol).

tftpd   TFTP server.

time   Run programs and summarize system resource usage.

timeout   Execute a command with a time limit.

times   Shows accumulated user and system times for the shell and it’s child processes.

tload   Shows a graph of the current system load average to the specified tty.

tmpwatch   Recursively remove files and directories which haven’t been accessed for the specified period of time.

top   Displays real-time view of processes running on the system.

touch   Change file access and modification times.

tput   Modify terminal-dependent capabilities, color, etc.

tr   Translate, squeeze, or delete characters from standard input and display on standard output.

tracepath   Traces path to a network host discovering MTU (Maximum Transmission Unit) along this path.

traceroute   Traces the route taken by the packets to reach the network host.

trap   Trap function responds to hardware signals. It defines and creates handlers to run when the shell receives signals.

troff   The troff processor of the groff text formatting system.

TRUE   Exit with a status code indicating success.

tset   Initialize terminal.

tsort   Perform topological sort.

tty   Display the filename of the terminal connected to standard input.

tune2fs   Adjust tunable filesystem parameters on ext2/ext3/ext4 filesystems.

tunelp   Set various parameters for the line printer devices.

type   Write a description for a command type.

#U

ul   Underline text.

ulimit   Get and set user limits for the calling process.

umask   Set file mode creation mask.

umount   Unmount specified file systems.

unalias   Remove alias definitions for specified alias names.

uname   Show system information.

uncompress   Uncompress the files compressed with the compress command.

unexpand   Convert spaces to tabs for a specified file.

unicode_start   Put keyboard and console in Unicode mode.

unicode_stop   Revert keyboard and console from Unicode mode.

uniq   Report or omit repeating lines.

units   Convert units from one scalar to another.

unrar   Extract files from a RAR archive.

unset   Remove variable or function names.

unshar   Unpack shell archive scripts.

until   Execute command until a given condition is true.

uptime   Tell how long the system has been running.

useradd   Create a new user or update default user information.

userdel   Delete a user account and related files.

usermod   Modify a user account.

users   Show the list of active users on the machine.

usleep   Suspend execution for microsecond intervals.

uudecode   Decode a binary file.

uuencode   Encode a binary file.

uuidgen   Created a new UUID (Universally Unique Identifier) table.

#V

vdir   Same as ls -l -b. Verbosely list directory contents.

vi   A text editor utility.

vidmode   Set the video mode for a kernel image. Displays current mode value without arguments. Alternative: rdev -v

vim   Vi Improved, a text-based editor which is a successor to vi.

vmstat   Shows information about processes, memory, paging, block IO, traps, disks, and CPU activity.

volname   Returns volume name for a device formatted with an ISO-9660 filesystem. For example, CD-ROM.

#W

w   Show who is logged-on and what they’re doing.

wait   Waits for a specified process ID(s) to terminate and returns the termination status.

wall   Display a message on the terminals all the users who are currently logged-in.

warnquota   Send mail to the users who’ve exceeded their disk quota soft limit.

watch   Runs commands repeatedly until interrupted and shows their output and errors.

wc   Print newline, word, and byte count for each of the specified files.

wget   A non-interactive file download utility.

whatis   Display one line manual page descriptions.

whereis   Locate the binary, source, and man page files for a command.

which   For a given command, lists the pathnames for the files which would be executed when the command runs.

while   Conditionally execute commands (while loop).

who   Shows who is logged on.

whoami   Displays the username tied to the current effective user ID.

whois   Looks for an object in a WHOIS database

write   Display a message on other user’s terminal.

#X

xargs   Runs a command using initial arguments and then reads remaining arguments from standard input.

xdg-open   Used to open a file or URL in an application preferred by the user.

xinetd   Extended internet services daemon. Works similar to inetd.

xz   Compress/ Decompress .xz and .lzma files.

#Y

yacc   Yet Another Compiler Compiler, a GNU Project parser generator.

yes   Repeatedly output a line with a specified string(s) until killed.

ypbind   A daemon that helps client processes to connect to an NIS server.

ypcat   Shows the NIS map (or database) for the specified MapName parameter.

ypinit   Sets up NIS maps on an NIS server.

ypmatch   Shows values for specified keys from an NIS map.

yppasswd   Change NIS login password.

yppasswdd   Acts as a server for the yppasswd command. Receives and executes requests.

yppoll   Shows the ID number or version of NIS map currently used on the NIS server.

yppush   Forces slave NIS servers to copy updated NIS maps.

ypserv   A daemon activated at system startup. It looks for information in local NIS maps.

ypset   Point a client (running ypbind) to a specifc server (running ypserv).

yptest   Calls various functions to check the configuration of NIS services.

ypwhich   Shows the hostname for NIS server or master server for a given map.

ypxfr   Transfers NIS server map from server to a local host.

#Z

zcat   Used to compress/uncompress files. Similar to gzip

zcmp   Compare compressed files.

zdiff   Compare compressed files line by line.

zdump   Displays time for the timezone mentioned.

zforce   Adds .gz extension to all gzipped files.

zgrep   Performs grep on compressed files.

zic   Creates time conversion information files using the specified input files.

zip   A file compression and packaging utility.

zless   Displays information of a compressed file (using less command) on the terminal one screen at a time.

zmore   Displays output of a compressed file (using more command) on the terminal one page at a time.

znew   Recompress .z files to .gz. files.