General user:
env – Show environment variables; run a program with altered environment variables
file <filename>– Determine the type of a file
nohup – Run a command with immunity to hangups outputting to non-tty
uptime – Print how long the system has been running
System management:
fuser – Identify processes by files or sockets
logger – Make entries in the system log
newgrp (or sg) – Log in to a new group
pathchk – Check the validity/portability of filenames
shutdown – turn off or reboot a system
shutdown -h now : it will shutdown the computer after shutting down all the services
poweroff -f : it will shutdown computer immediately without looking into the services.
Kernel specific:
date – Print or set the system date and time
dmesg – Print the kernel message ring buffer
ipcrm – Remove a message queue, semaphore set or shared memory ID
ipcs – Provide information on IPC facilities
uname -a : Print assorted system statistics
Processes and task management:
at – Single-time command scheduler
chroot – Change the system root directory for all child processes
cron – Periodic command scheduler
crontab – Crontab file editor
exit – Terminate the current shell process
kill – Send a signal to process, or terminate a process (by PID)
killall – Terminate processes by name (in GNU/Linux)
nice – Alter priorities for processes
pgrep – Find PIDs of processes by name
pkill – Send a signal to process, or terminate a process. Equivalent to Linux killall
ps – Report process status
renice – Alter the priorities of an already running process
sleep – Delay for specified time
time – Time a command
timex – Time process shell execution, measure process data and system activity
top – Produce a dynamic list of all resident processes
wait – Wait for the specified process
watch – Run the specified command repeatedly
Job Control
bg – Resume a job in background
jobs – List active jobs
fg – Resume a job in foreground
User management and support
chsh – Change user shell
finger – Get details about user
id – Print real/effective UIDs/GIDs
last – Show listing of last logged in users
lastlog – Show last log in information for users
locale – Get locale specific information
localedef – Compile locale definitions
logname – Print user’s login name
mesg – Control write access to your terminal
passwd – Change user password
su – Start a new process (defaults to shell) as a different user (defaults to root)
sudo – Execute a command as a different user
users – Show who is logged on (only users’ names)
w – Show logged-in users and their current tasks
whatis – Print command description from whatis database
whereis – Locate the command’s binary and the manual pages associated with it
which – Locate where a command is executed from
who – Show who is logged on (with some details)
whoami – Show the user’s login name
write – Send a message to another user
Terminal configuration
stty – Change and print terminal line settings
tput – Initialize a terminal/query terminfo database
tty – Print filename of terminal connected to standard input
Files and texts
info – The GNU alternative to man
man – The standard unix documentation system
Filesystem Utilities
chattr – Change file attributes on a Linux second extended file system
chgrp – Change the group of a file or directory
chmod – Change the permissions of a file or directory
chown – Change the owner of a file or directory
cd – Change to another directory location
cp – Copy a file or directory to another location
dd – Convert and copy a file in blocks
df – Report disk space
dircmp – Compare contents of files between two directories
du – Calculate used disk space
fdupes – Find or remove duplicate files within a directory
find – Search for files through a directory hierarchy
fsck – Check filesystem
fstat – Identify open files
link – Link one file/directory to another (privileged user only)
ln – Link one file/directory to another
ls – List directory contents
lsattr – List file attributes on a Linux second extended file system
lsof – List open files
mkdir – Make a directory
mkfifo – Make a named pipe
mount – Mount a filesystem
mv – Move or rename a file or directory
pwd – Print the current working directory
rm – Delete a file or directory tree
readlink – Display value of a symbolic link, or display canonical path for a file
rmdir – Delete an empty directory
touch – Create a new file or update its modification time
tree – Print a depth-indented tree of a given directory
unlink – System call to remove a file or directory
Archivers and compression
afio – Compatible superset of cpio with added functionality
ar – Maintain, modify, and extract from static library files (historically also used for archives of other file types)
bzip2 – Compress files by block-sorting
compress – Compress files using the LZW algorithm
cpio – A traditional archiving tool/format
gzip – The gzip file compressor
pack, pcat, unpack – included in old versions of ATT Unix. Uses Huffman coding, obsoleted by compress.
pax – POSIX archive tool that handles multiple formats.
tar – Tape ARchiver, concatenates files
uncompress – Uncompress files compressed with compress.
zcat – Print files to stdout from gzip archives without unpacking them to separate file(s)
Text Processing
awk – A pattern scanning and processing language
banner – Create ascii art version of an input string for printing large banners
cat – Concatenate files to standard output
cksum – Print the CRC checksum and bytecount of a file (see also MD5)
cmp (Unix) – Compare two files byte for byte
comm – Sort two files and compare them line for line
csplit – Split a file into sections determined by context lines
cut – Remove sections from each line of a file or standard input
diff3 – Compare one text file against two other files
diff – Compare two text files line by line
egrep – Extended pattern matching (synonym for “grep -E”)
expand – Convert tabs to spaces
fc – Process the command history list
fgrep – Simplified pattern matching (synonym for “grep -F”)
fold – Wrap each input line to fit within the given width
grep – Print lines matching a pattern
head – Output the first parts of a file
iconv – Convert the encoding of the specified files
join – Join lines of two files on a common field
less – Improved more-like text pager
merge – Three-way merge of files (see also paste)
more – Pager
nkf – Convert Japanese characters
nl – Number the lines of a file
nroff – Fixed-width (non-typesetter) version of the standard Unix typesetting system
od – Dump files in various formats, e.g. octal
paste – Merge lines of files
patch – Change files based on a patch file
rev – Reverse lines of a file
sed – Stream EDitor
sort – Sort lines of text files
split – Split a file into pieces
tac – cat in reverse — display files to standard output in reverse order starting at the end of the file
tail – Output the tail end of files
tee – Read from standard input, write to standard output and files
tr – Translate characters
tsort – Perform a topological sort
unexpand – Convert spaces to tabs
uniq – Remove duplicate lines from a sorted file
uudecode – Decode a binary file that was used for transmission using electronic mail
uuencode – Encode a binary file for transmission using electronic mail
wc – Count words, lines and bytes
Text editors
acme – Bitmapped text editor and integrated development environment ported from the Plan 9 operating system with client-server design, by Rob Pike. This is the successor of sam.
ed – Original line-oriented, regular-expression based Unix text editor
ex – Line-oriented text editor from BSD Unix, originally derived from Unix ed, later augmented by a screen-oriented “visual” mode, creating vi; typically a symbolic link to vi (or vim) causing it to start up in line-editing mode
GNU Emacs – Freely programmable full-screen text editor and general computing environment (using builtin Elisp, a simple dialect of the Lisp programming language)
Joe – A screen-oriented text editor using a Wordstar-style command set
Jove – A screen-oriented text editor using an Emacs-style command set
MicroEMACS – A screen-oriented text editor using an Emacs-style command set
nano – Clone of pico (see below)
NEdit – A Motif based text editor for the X11 windowing system, remniscient of text editors on Mac or Windows systems
nvi – “New” vi, unencumbered (no remaining original Unix code) reimplementation of ex/vi for the 4.4BSD operating system release
pico – PIne’s message COmposition editor (simple, easy to use screen editor)
sam – Bitmapped multifile text editor with client-server design, by Rob Pike
vi – “Visual” (screen-oriented) text editor (originally ex in screen-oriented “visual” mode)
VILE – “Vi Like Emacs”, a vi-like text editor that has been derived from the MicroEMACS text editor
vim – Vi IMproved, portable vi-compatible editor with multiple buffers, screen splitting, syntax highlighting and a lot of other features not found in standard ex/vi
XEmacs – Popular version of emacs that is derived from GNU Emacs
Communication, networking and remote access
Apache – A web server for Unix-like systems
efax – Integrated fax program
ftp, sftp – File transfer protocol, SSH file transfer protocol
HylaFAX – Fax server
minicom – Connect directly to a computer via modem
netcat – Versatile network utility for reading from and writing to network connections
NFS – Network filesystem
OpenVPN – Virtual private (encrypting) networking software
Postfix – Mail transfer agent
rsh, SSH, telnet – Remote login software
Samba – SMB and CIFS client and server for UNIX
Sendmail – Popular email transport software
talk – Utility that allows talking to another logged-in user
uustat – A Basic Networking Utilities (BNU) command that displays status information about several types of BNU operations
uucp – File transfer utility (Unix-to-Unix Copy)
uux – Remote command execution over UUCP
E-mail clients
elm – Screen-oriented mail program that used to be very popular
mail – Original Unix email program
mailx/Mail – Improved version of Unix mail program from BSD Unix
mh – A message handler
Mulberry – Powerful graphical IMAP-centric e-mail client (recently released as open source)
Mutt – Screen-oriented mail program
nmh – A new message handler
Opera – Web browser and e-mail client (proprietary)
Pine – Screen-oriented mail and news program, originally derived from elm
procmail – Automatic mail sorting
Mozilla Thunderbird – Extensible e-mail client
Network system services
fingerd – A daemon for finger – a program used to return a human-readable status report on either the system at the moment or a particular person in depth
inetd – A daemon on many Unix systems that manages Internet services
xinetd – Replacement for inetd
{ For edit the section, register yourself } Network Utilities
authbind – Used to authorize non-root users to use port numbers below 1024
dhclient – A DHCP client
dhcpd – The DHCP daemon
dhcpcd – A DHCP client-daemon
ifconfig – A tool used to configure a network interface for TCP/IP
iwconfig – Similar to ifconfig, but is dedicated to wireless networking interfaces
ping – A network tool that tests of whether a particular host is up and reachable on the network
pppd – Point-to-Point Protocol daemon
tcpd – Secures programs launched from inetd
{ For edit the section, register yourself } Network monitoring and security
Ethereal and tethereal – A packet sniffer deprecated in favor of a fork called Wireshark
ettercap – A tool for network protocol analysis
John the Ripper – Password-cracking software
Nessus – A comprehensive open-source network vulnerability scanning program
Netstat – Displays a list of the active network connections the computer
Nmap – Free port scanning software
SAINT – System Administrator’s Integrated Network Tool – Network Vulnerability Scanner.
SATAN – the Security Administrator Tool for Analyzing Networks – A testing and reporting tool that collects information about networked hosts
Snoop – Solaris packet sniffer
Snort – An open source network intrusion detection system
tcpdump – A computer network debugging tool that intercepts and displays TCP/IP packets being transmitted or received
Wireshark – A protocol analyzer with GUI frontend and various sorting and filtering options that was forked from Ethereal by its original author.
Script Interpreters
printf – Format and print data
strings – Print strings of printable characters found in a file
test – Test an expression
times – Prints information about the current shell execution’s time
true – Return a value that evaluates as True
unset – Unset a shell variable
xargs – Build and execute command lines from standard input
expr – Evaluate expressions
User interfaces
X11 – Graphical user interface (GUI)
o startx and xinit
o xterm
Desktops/Graphical User Interfaces
4dwm – Variant of the Motif Window Manager found on Silicon Graphics’ IRIX operating system
Blackbox and its variants (including Fluxbox and Waimea)
CDE – Common Desktop Environment, most commonly found on proprietary UNIX systems
dfm – Desktop File Manager resembling OS/2 and designed to work with IceWM
EDE – Small desktop environment that is meant to be simple and fast
Enlightenment – an open source window manager for the X Window System
FVWM – Virtual window manager
FVWM95 – Window manager designed to behave like Windows 95
FVWM-Crystal – Flashy window manager
GNOME – GNU Network Object Model Environment
IceWM – ICE Window Manager
Ion (window manager) – Tiling and tabbing window manager for the X Window System, designed for use without a mouse
JWM – Joe’s Window Manager
KDE – K Desktop Environment
MWM – Motif Window Manager
Quartz Compositor – Apple’s GUI interface for the Darwin BSD based operating system Mac OS X
Window Maker – Window manager designed to emulate NeXT’s GUI
WMI – Window Manager Improved
XFce – A desktop environment for Unix and other Unix-like platforms
Secutiry
ClamAV – open-source virus scanner
Enigmail – Graphical interface to gpg for Mozilla Application Suite and Mozilla Thunderbird
gpg – GNU Privacy Guard, a complete and free replacement for PGP (to do file and email encryption and signature).
mcrypt – Replacement for the legacy crypt program; can also make OpenPGP-compatible files.
openssl – Secure Sockets Layer and general crypto library.
pinepgp – Filters that enable pine to use signed/encrypted email.
Package management software
apt – Front-end for dpkg or rpm
debconf – Debian package configuration management system
dpkg – The Debian package manager
drakconf – Front-end configuration utility for Mandriva Linux
GNU Stow – Link applications from specific directories into a common directory
emerge – A frontend to portage
pacman – A package manager used primarily by Arch Linux
portage – The Gentoo Linux package manager
rpm – Originally the package manager for Red Hat Linux, now used by several distributions including Mandriva Linux
Synaptic – GTK+ frontend for the apt package manager. Primarily used by Ubuntu Linux, Debian Sarge, and other Debian-based systems; but usable on any system using apt
urpmi – Front-end to rpm, used by Mandriva Linux
YaST – System management utility mainly used by SuSE
yum – Front-end for rpm, used by Fedora
OS X/Darwin specific programs
defaults – Access the Mac OS X user defaults system
fink – The Fink package manager
open – Opens argument(s) in the GUI as if the user had double clicked
osacompile – Compile AppleScripts and other OSA language scripts
osalang – Information about installed OSA languages
osascript – Execute AppleScripts and other OSA language scripts
say – Convert text to audible speech
Desktop Publishing
LaTeX – Popular TeX macro package for higher-level typesetting
lp – Print a file (on a line printer)
Passepartout – Desktop publishing program
pr – Convert text files for printing
Scribus – Desktop publishing program
TeX – Macro-based typesetting system
troff – The original and standard Unix typesetting system
Desktop utilities
bc – An arbitrary precision calculator language with syntax similar to the C programming language
cal – Display a calendar
dc – Reverse-Polish desk calculator which supports unlimited precision arithmetic
fortune – Fortune cookie program that prints a random quote
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