Unix - Useful Commands

This quick guide lists commands, including a syntax and brief description. For more detail, use −

$man command

Files and Directories

These commands allow you to create directories and handle files.

Command	Description
cat	Display File Contents
cd	Changes Directory to dir name
chgrp	change file group
chmod	Changing Permissions
cp	Copy source file into destination
file	Determine file type
find	Find files
grep	Search files for regular expressions.
head	Display first few lines of a file
ls	Display information about file type.
mkdir	Create a new directory dirname
more	Display data in paginated form.
mv	Move (Rename) a oldname to newname.
pwd	Print current working directory.
rm	Remove (Delete) filename
rmdir	Delete an existing directory provided it is empty.
tail	Prints last few lines in a file.
touch	Update access and modification time of a file.

Manipulating data

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

Command	Description
awk	Pattern scanning and processing language
cmp	Compare the contents of two files
comm	Compare sorted data
cut	Cut out selected fields of each line of a file
diff	Differential file comparator
expand	Expand tabs to spaces
join	Join files on some common field
sort	Sort file data
split	Split file into smaller files
wc	Count words, lines, and characters
vi	Opens vi text editor
vim	Opens vim text editor

Compressed Files

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

Command	Description
compress	Compress files
gunzip	Uncompress gzipped files
gzip	GNU alternative compression method
uncompress	Uncompress files
unzip	List, test and extract compressed files in a ZIP archive
zcat	Cat a compressed file
zcmp	Compare compressed files
zdiff	Compare compressed files
zmore	File perusal filter for crt viewing of compressed text

Network Communication

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

Command	Description
ftp	File transfer program
rcp	Remote file copy
rlogin	Remote login to a UNIX host
rsh	Remote shell
telnet	Make terminal connection to another host
ssh	Secure shell terminal or command connection
scp	Secure shell remote file copy
sftp	secure shell file transfer program

Misc Commands

These commands list or alter information about the system

Command	Description
chgrp	Change the group ownership of a file
chown	Change owner
date	Print the date
du	Print amount of disk usage
echo	Echo arguments to the standard options
exit	Quit the system
Show group memberships
homequota	Show quota and file usage
iostat	Report I/O statistics
kill	Send a signal to a process
last	Show last logins of users
logout	log off UNIX
netstat	Show network status
passwd	Change user password
passwd	Change your login password
printenv	Display value of a shell variable
ps	Display the status of current processes
top	Display all system processes
umask	Show the permissions that are given to view files by default
uname	Display name of the current system
uptime	Get the system up time
useradd	Create a user account
users	Print names of logged in users
vmstat	Report virtual memory statistics
w	Show what logged in users are doing
who	List logged in users