Unix - Useful Commands


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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 −

td>groups
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