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 dirname
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
ln	Create softlink on oldname
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
perl	Data manipulation language
sed	Stream text editor
sort	Sort file data
split	Split file into smaller files
tr	Translate characters
uniq	Report repeated lines in a file
wc	Count words, lines, and characters
vi	Opens vi text editor
vim	Opens vim text editor
fmt	Simple text formatter
spell	Check text for spelling error
ispell	Check text for spelling error
ispell	Check text for spelling error
emacs	GNU project Emacs
ex, edit	Line editor
emacs	GNU project Emacs
emacs	GNU project Emacs

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

Getting Information

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

Command	Description
apropos	Locate commands by keyword lookup
info	Displays command information pages online
man	Displays manual pages online
whatis	Search the whatis database for complete words.
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.

Command	Description
ftp	File transfer program
rcp	Remote file copy
rlogin	Remote login to a UNIX host
rsh	Remote shell
tftp	Trivial file transfer program
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

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 -

Command	Description
evolution	GUI mail handling tool on Linux
mail	Simple send or read mail program
mesg	Permit or deny messages
parcel	Send files to another user
pine	Vdu-based mail utility
talk	Talk to another user
write	Write message to another user

Programming Utilities

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

Command	Description
dbx	Sun debugger
gdb	GNU debugger
make	Maintain program groups and compile programs.
nm	Print program's name list
size	Print program's sizes
strip	Remove symbol table and relocation bits
cb	C program beautifier
cc	ANSI C compiler for Suns SPARC systems
ctrace	C program debugger
gcc	GNU ANSI C Compiler
indent	Indent and format C program source
bc	Interactive arithmetic language processor
gcl	GNU Common Lisp
perl	General purpose language
php	Web page embedded language
py	Python language interpreter
asp	Web page embedded language
CC	C++ compiler for Suns SPARC systems
g++	GNU C++ Compiler
javac	JAVA compiler
appletvieweir	JAVA applet viewer
netbeans	Java integrated development environment on Linux
sqlplus	Run the Oracle SQL interpreter
sqlldr	Run the Oracle SQL data loader
mysql	Run the mysql SQL interpreter

Misc Commands

These commands list or alter information about the system -

Command	Description
chfn	Change your finger information
chgrp	Change the group ownership of a file
chown	Change owner
date	Print the date
determin	Automatically find terminal type
du	Print amount of disk usage
echo	Echo arguments to the standard options
exit	Quit the system
finger	Print information about logged-in users
groupadd	Create a user group
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
lun	List user names or login ID
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
ps	Print process status statistics
quota -v	Display disk usage and limits
reset	Reset terminal mode
script	Keep script of terminal session
script	Save the output of a command or process
setenv	Set environment variables
stty	Set terminal options
time	Time a command
top	Display all system processes
tset	Set terminal mode
tty	Print current terminal name
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