Unix / Linux - Useful Commands

Files and Directories

These commands allow you to create directories and handle files.

Given below is the list of commands in Files and Directories.

Sr.No.	Command & Description
1	cat Displays File Contents
2	cd Changes Directory to dirname
3	chgrp Changes file group
4	chmod Changes permissions
5	cp Copies source file into destination
6	file Determines file type
7	find Finds files
8	grep Searches files for regular expressions
9	head Displays first few lines of a file
10	ln Creates softlink on oldname
11	ls Displays information about file type
12	mkdir Creates a new directory dirname
13	more Displays data in paginated form
14	mv Moves (Renames) an oldname to newname
15	pwd Prints current working directory
16	rm Removes (Deletes) filename
17	rmdir Deletes an existing directory provided it is empty
18	tail Prints last few lines in a file
19	touch Updates access and modification time of a file

Manipulating data

The contents of files can be compared and altered with the following commands.

Given below is the list of commands in Manipulating data.

Sr.No.	Command & Description
1	awk Pattern scanning and processing language
2	cmp Compares the contents of two files
3	comm Compares sorted data
4	cut Cuts out selected fields of each line of a file
5	diff Differential file comparator
6	expand Expands tabs to spaces
7	join Joins files on some common field
8	perl Data manipulation language
9	sed Stream text editor
10	sort Sorts file data
11	split Splits file into smaller files
12	tr Translates characters
13	uniq Reports repeated lines in a file
14	wc Counts words, lines, and characters
15	vi Opens vi text editor
16	vim Opens vim text editor
17	fmt Simple text formatter
18	spell Checks text for spelling error
19	ispell Checks text for spelling error
20	emacs GNU project Emacs
21	ex, edit Line editor
22	emacs GNU project Emacs

Compressed Files

Files may be compressed to save space. Compressed files can be created and examined.

Sr.No.	Command & Description
1	compress Compresses files
2	gunzip Helps uncompress gzipped files
3	gzip GNU alternative compression method
4	uncompress Helps uncompress files
5	unzip List, test and extract compressed files in a ZIP archive
6	zcat Cat a compressed file
7	zcmp Compares compressed files
8	zdiff Compares compressed files
9	zmore File perusal filter for crt viewing of compressed text

Getting Information

Various Unix manuals and documentation are available on-line. The following Shell commands give information −

Sr.No.	Command & Description
1	apropos Locates commands by keyword lookup
2	info Displays command information pages online
2	man Displays manual pages online
3	whatis Searches the whatis database for complete words
4	yelp GNOME help viewer

Network Communication

These following commands are used to send and receive files from a local Unix hosts to the remote host around the world.

Sr.No.	Command & Description
1	ftp File transfer program
2	rcp Remote file copy
3	rlogin Remote login to a Unix host
4	rsh Remote shell
5	tftp Trivial file transfer program
6	telnet Makes terminal connection to another host
7	ssh Secures shell terminal or command connection
8	scp Secures shell remote file copy
9	sftp Secures shell file transfer program

Some of these commands may be restricted at your computer for security reasons.

Messages between Users

The Unix systems support on-screen messages to other users and world-wide electronic mail −

Sr.No.	Command & Description
1	evolution GUI mail handling tool on Linux
2	mail Simple send or read mail program
3	mesg Permits or denies messages
4	parcel Sends files to another user
5	pine Vdu-based mail utility
6	talk Talks to another user
7	write Writes message to another user

Programming Utilities

The following programming tools and languages are available based on what you have installed on your Unix.

Given below is the list of tools and languages in Programming Utilities.

Sr.No.	Command & Description
1	dbx Sun debugger
2	gdb GNU debugger
3	make Maintains program groups and compile programs
4	nm Prints program's name list
5	size Prints program's sizes
6	strip Removes symbol table and relocation bits
7	cb C program beautifier
8	cc ANSI C compiler for Suns SPARC systems
9	ctrace C program debugger
10	gcc GNU ANSI C Compiler
11	indent Indent and format C program source
12	bc Interactive arithmetic language processor
13	gcl GNU Common Lisp
14	perl General purpose language
15	php Web page embedded language
16	py Python language interpreter
17	asp Web page embedded language
18	CC C++ compiler for Suns SPARC systems
19	g++ GNU C++ Compiler
20	javac JAVA compiler
21	appletvieweir JAVA applet viewer
22	netbeans Java integrated development environment on Linux
23	sqlplus Runs the Oracle SQL interpreter
24	sqlldr Runs the Oracle SQL data loader
25	mysql Runs the mysql SQL interpreter

Misc Commands

These commands list or alter information about the system −

Given below is the list of Misc Commands in Unix.

Sr.No.	Command & Description
1	chfn Changes your finger information
2	chgrp Changes the group ownership of a file
3	chown Changes owner
4	date Prints the date
5	determin Automatically finds terminal type
6	du Prints amount of disk usage
7	echo Echo arguments to the standard options
8	exit Quits the system
9	finger Prints information about logged-in users
10	groupadd Creates a user group
11	groups Show group memberships
12	homequota Shows quota and file usage
13	iostat Reports I/O statistics
14	kill Sends a signal to a process
15	last Shows last logins of users
16	logout Logs off Unix
17	lun Lists user names or login ID
18	netstat Shows network status
19	passwd Changes user password
20	passwd Changes your login password
21	printenv Displays value of a shell variable
22	ps Displays the status of current processes
23	ps Prints process status statistics
24	quota -v Displays disk usage and limits
25	reset Resets terminal mode
26	script Keeps script of terminal session
27	script Saves the output of a command or process
28	setenv Sets environment variables
30	stty Sets terminal options
31	time Helps time a command
32	top Displays all system processes
33	tset Sets terminal mode
34	tty Prints current terminal name
35	umask Show the permissions that are given to view files by default
36	uname Displays name of the current system
37	uptime Gets the system up time
38	useradd Creates a user account
39	users Prints names of logged in users
40	vmstat Reports virtual memory statistics
41	w Shows what logged in users are doing
42	who Lists logged in users

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