UNIX Command Reference

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UNIX command line reference links to explanations. The list below is an excerpt from the rich command line set and will be changed constantly.

A

Command	Description	Extra
ack	A better than grep implementation. See also UNIX ack	NCyg
admin	Administer SCCS files.	NCyg
apt	Package managing system	NCyg
ar	Maintain, modify, and extract from archives. Now largely obsoleted by tar.	Cyg
as	GNU assembler tool. Also known as Gas.	Cyg
at	Single-time command scheduler	Cyg
awk	Pattern scanning and processing language. See also AWK.	Cyg.

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B

Command	Description	Extra
banner	Creates ascii art version of an input string for printing large banners	Cyg
basename	Returns the final component of a path	Cyg
batch	Runs jobs when the system load level permits	NCyg
bc	An arbitrary precision calculator language with syntax similar to the C programming language.	Cyg

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C

Command	Description	Extra
cal	Displays a calendar	NC
cat	Concatenates files to standard output. Example:cat fileIn | sort -u > FileOut.uniq	Cyg
cc	C-compiler	Cyg
cd	Changes the directory	Cyg
chmod	Change the permissions of a file or directory. See the table below for all combinations/settings. The roles are: u for users g for group o for others a all which is used in chmod as the combination for ufo'. # rwx Permission rwx 7 rwx full 111 6 rw. read and write 110 5 r.x read and execute 101 4 r.. read only 100 3 .wx write and execute 011 2 .w. write only 010 1 ..x execute only 001 0 ... none 000 So: Command Result Description chmod u+x chmod 100 ---x------ Gives the User permission to eXecute chmod u+r,g+x chmod 510 -r-x--x--- Gives extra read access (existing access 'execute' to the user, and grant execute access to the group. chmod u-rx chmod 010 ------x--- Removes the read and execute from user, without changing the granted group access. chmod a+x chmod 111 ---x--x--x Grants execute rights to all. chmod --reference   Make the file permissions of file2 exactly the same as file 1.	Cyg
chown	Change the owner of a file or directory	Cyg
cksum	Print the CRC checksum and bytecount of a file (see also MD5)	Cyg
clear	Clears the content of the screen	Cyg
cmp	Compares two files byte for byte	Cyg
comm	Sorts two files and compare them line for line	Cyg
cp	Copies a file or directory to another location. To copy directories recursive use: cp -r xxx yyy	Cyg
crontab	Schedules commands to be executed periodically.	NC
crypt	Crypts or decrypts a data	NC
csh	C shell (csh) is a Unix shell developed by Bill Joy for the BSD Unix system.	NC
csplit	csplit separates a file into sections and place the sections into files names xx00 through xx99.	Cyg
ctags	Generate tags file summarising location of objects in source files.	NC
cut	cut extract a certain range of characters from a line, usually from a file.	Cyg

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D

Command	Description	Extra
date	Print or set the system date and/or time	Cyg
dbx	(System V and BSD) Symbolic debugger.	NC
dc	Reverse-Polish desk calculator which supports unlimited precision arithmetic	Cyg
dd	Converts and copies a file (Disk Dump). A powerful low-level tool for cloning hrd disks.	Cyg
df	Displays the amount of disk space used and available on the filesystems accessible to a user.	Cyg
diff	Reports the line difference between 2 files.	Cyg
diff3	Compares three files and report the differences.	Cyg
dircmp	Compares the contents of files between two directories	Cyg
dirname	Strips non-directory suffixes from a path	Cyg
du	estimate the file space usage	Cyg

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E

Command	Description	Extra
echo	Print to standard output	Cyg
ed	Standard text editor. See also ex.	NC
env	Show environment variables; run a program with altered environment variables	Cyg
eqn	Part of the troff suite of Unix document layout tools, eqn is a preprocessor that formats equations for printing. A similar program, neqn, accepted the same input as eqn, but produced output tuned to look better in nroff. eqn was created by Brian Kernighan and Lorinda Cherry.	Cyg
ex	Advanced version of the standard Unix editor ed,	Cyg
expr	Evaluates an expression	Cyg

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F

Command	Description	Extra
factor (num)	Produce the prime factors of num.	Cyg
fc	Processes the command history list	Cyg
fgrep	Simplified pattern matching (synonym for "grep -F")	Cyg
file	Determine the type of a file, (See also stat)	Cyg
find	Search for files through a directory hierarchy. One of the most complicated UNIX commands, See also GNU Find. An alternative GUI find is SearchMonkey. See also xargs, and the Examples.	Cyg
finger	Displays data about one or more users, including information listed in the files. Also the shell you are currently using (finger -m <username>)	Cyg
fit	fmt fills and joins text, producing lines of roughly the same length.	Cyg
fold	Fold breaks the lines of the named files so that they are no wider than the specified width.	Cyg
ftp	ftp transfers files to and from remote network site hostname.	Cyg

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G

Command	Description	Extra
Gedit	gedit is the official text editor of the GNOME desktop environment. Is also available for Windows, MacOS.	Ubuntu
getopts	Retrieves options and option-arguments from a list of parameters.	Cyg
gprof	Display call-graph profile data of C programs.	Cyg
grep	grep takes a regular expression on the command line, reads standard input or a list of files, and outputs the lines containing matches for the regular expression.	Cyg
groups	Show the groups that user belongs to (default is your groups). Groups are listed in /etc/passwd and /etc/group.	Cyg

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H

Command	Description	Extra
head	Output the first parts of a file.	Cyg
help	Display helpful information about builtin commands.	Cyg
hostid	Print the hexadecimal ID number of the host machine.	Cyg

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I

Command	Description	Extra
iconv	Convert the encoding of the specified files	Cyg
id	Prints the UID of the account of which the program is executed by.	Cyg
install	Install] copies files and set attributes	Cyg
ipcrm	Removes a message queue, semaphore set or shared memory id.	Cyg
ipcs	Provides information on IPC facilities	Cyg

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J

Command	Description	Extra
join	Joins lines of two files on a common field	Cyg

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K

Command	Description	Extra
kill	Sends a message normaly a termination signal (message) to a program	Cyg
ksh	Korn shell, standard shell on many proprietary Unix systems, powerful successor to the Unix Bourne shell (sh), written by David Korn,	NC

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L

Command	Description	Extra
ld	Program linker	Cyg
less	Shows the content of a file on the terminal screen.	Cyg
ln	Creates symbolic links.	Cyg
login	Logs in to the system	Cyg
logname	Logname prints the user login name	Cyg
lp	Prints a file (on a line printer)	NC
ls	Lists segments or lists files (directories). Examples: Show symbolic links: ls -l . | grep ">" Alias example for showing all information: alias la='ls -al ' Alias example for shwing alias lr='ls -l | wc' The meaning of all fields of ls -Al common known as the alias la. Type User Group Other ldc r w x r w x r w x [1] [2] [3] [4] [1] The type of the entry, a symbol link (l), a directory (d) or a character file (c) [2] The user rights for read, write and execute. [3] The group rights for read, write and execute. [4] The other rights for read, write and execute. The full signature of the la -Al can be: lrwxrwxrwx owner group 12345 Feb 26 07:08 file1 Meaning: owner the name of the owner of the file, use the chown command to change (i.e.: chown root file) group, the group to which the file belongs, use the chown command to change (i.e. chown :friends file). 12345, the size of the file, edit the file to change Feb 26 07:08, the creation date of the file, use touch to change file1, the filename of the file, use mv to change (i.e. mv file1 file2).	Cyg

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M

Command	Description	Extra
mail	Unix standard mail client. Examples Mail	NC
mailx	Improved mail client	NC
make	Automates builds. See the GNU Make Wiki page.	Cyg.
man	Displays extensive documentation on commands	Cyg
mkdir	Makes a (sub)directory	Cyg
more	Displays the named files on a terminal, one screenful at a time.	Cyg
mv	Moves a file or directory from one place to another.	Cyg

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N

Command	Description	Extra
nice	maps to a kernel call of the same name.	Cyg
nl	Numbers the lines of a file.	Cyg
nohup	Run a command with immunity to hangups outputting to non-tty	Cyg

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O

Command	Description	Extra

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P

Command	Description	Extra
Periodic	Runs periodic system functions Example: sudo periodic daily weekly monthly
ps	Process Status displays the currently-running processes. Example to show if cron is running: ps -el | grep cron

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Q

Command	Description	Extra

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R

Command	Description	Extra
replace	KSH replaces characters/text in a string. This KSH option is a feature of the shell. See the kWh manual. Examples are: Replaces 1st occurrence of text in string: ${string/find/replace} Replaces all occurrences of text in string: ${string//find/replace}	KSH Only.
rm	Removes a file (file list).
rsync	rsync synchronizes files and directories from one location o another while minimizing data transfer by using the delta encoding when appropriate. For examples look at Unix rsync

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S

Command	Description	Extra
sh	Bourne shell, the standard Unix shell
scp	Secure Copy or SCP is a means of securely transferring computer files between a local and a remote host or between two remote hosts, using the Secure Shell (SSH) protocol. scp SourceFile user@host:directory/TargetFile scp user@host:folder/SourceFile TargetFile	See also Secure copy for secure copy without Password.
sed	Sed reads text input, line by line, either from a file or a stream, into an internal buffer called the pattern space. Each line read starts a cycle. To the pattern space, sed applies one or more operations which have been specified via a sed script. sed implements a programming language with about 25 commands that specify the operations on the text. When the sed script ends, sed outputs the pattern space, and reads the next line into the pattern space, starting a new cycle.
split	Split a large file into smaller parts. Examples: split -b 22 newfile.txt new Split the file "newfile.txt" into three separate files called newaa, newab and newac each file the size of 22. split -l 300 file.txt new Split the file "newfile.txt" into files beginning with the name "new" each containing 300 lines of text each split -b 720mb file.zip parts Split the file "file.zip" into files beginning with the name "parts" each containing 720Mb. In windows combine the file using: copy /b file1+file2 result
strings	Shows all string in a binary dump. strings dd_onbz.dmp | less -f
sudo	The sudo command is a program for some UNIX and Unix-like computer operating systems that allows users to run programs with the security privileges of another user (normally the superuser, or root). See also: Sudo manpage, Ubuntu Karmic sudo manpage and SuDo Home Page .
sysv-rc-conf	sysv-rc-conf gives an easy to use interface for managing etc/rc{runlevel}.d/ symlinks. The interface comes in two different flavors, one that simply allows turning services on or off and another that allows for more fine tuned management of the symlinks. It’s a replacement for programs like ntsysv(8) or rcconf(8). See also Linux startup process.	Ubuntu

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T

Command	Description	Extra
tail	Tails to see and follow (-f) the lines of a logfile.	Cyg
Test	The test command in Unix evaluates the expression parameter. In some shells such as FreeBSD sh(1) it is a shell builtin, even though the external version still exists. In the second form of the command, the [ ] (brackets) must be surrounded by blank spaces. This is because [ is a program and POSIX compatible shells require a space between the program name and its arguments. One must test explicitly for file names in the C shell. File-name substitution (globbing) causes the shell script to exit.
tr	Translate, squeeze, and/or delete characters from standard input, writing to standard output. Example: tr -cs "[:alpha:]" "[\n*]" < input > output	Cyg

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U

Command	Description	Extra
uptime	Print how long the system has been running

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V

Command	Description	Extra
vi	vi is a family of screen-oriented text editors. See the internal wiki page on vi.	Cyg
visudo	visudo edits the sudoers file in a safe fashion, analogous to vipw. Visudo locks the sudoers file against multiple simultaneous edits, provides basic sanity checks, and checks for parse errors. If the sudoers file is currently being edited you will receive a message to try again later.	Ubuntu

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W

Command	Description	Extra
wc	Unix Word Count, showing the number of lines, words and bytes. Example: wc foo bar	Cygwin
Whois	Who is gives the owner/user of an IP-address. See the Whois-wiki page for detailed information on whois and the available free and paid services.	Cygwin

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X

Command	Description	Extra
xargs	xargs reads items from the standard input, delimited by blanks or newlines and executes the command one or more times. xargs is useful when passing large number of arguments to a command. See also Find and the examples.

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Z

Command	Description	Extra
zip	ZIP managess package and compress (archive) files

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See also

• List of UNIX Programs
• Examples Find, One of the powerful UNIX commands is find. But there are a few people knowing every trick f it. Here some basic examples.
• Examples Mail, How to send a mail with attachment and more.
• UNIX Compendium, by Mark Burgess, Edition 2.2, August 2001, Edited by Harm Frielink