Unix - Useful Commands


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

$man command

Files and Directories

These commands allow you to create directories and handle files.

S.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.

S.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.

S.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 −

S.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.

S.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 −

S.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.

S.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 −

S.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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