08 unix commands

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Revision no.: PPT/2K403/02Revision no.: PPT/2K605/03

UNIX Commands


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Revision no.: PPT/2K605/03

CMS INSTITUTE, 2006. All rights reserved. No part of this material may be reproduced, stored or emailed without the prior permission of Programme Director, CMS Institute

Introduction

UNIX system provides the user with a number of powerful

commands to examine and maintain files efficiently.

Commands take a stream of characters as input and generate

a stream of characters as output.

UNIX shell usually treats the terminal keyboard as standard

input and the terminal screen as standard output.

Standard error is displayed, by default on the standard output

which may be redirected to an output file.


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Basic UNIX Commands


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cat

Syntax

cat [options] [file 1 file2 file3 .......... ]

Displays text file contents or copies the contents of file1 into

file2.

Example

To display the contents of the file named poem.

$cat poem


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chdir/cd

Syntax

cd pathname

Used to change the working directory.

Example

To return to your home directory

$cd

To change to misc directory by specifying the pathname along

with the command.

$cd misc


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clear

Syntax

Clear

To clear the screen

Example

To clear the screen on the monitor.

$clear


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cp

Syntax

cp file1 file2

Used to create duplicate copies of files.

Example

To copy the contents of File A to File B.

$copy fileA fileB

If the File B exists, the contents of FileB are erazed and the

contents of FileA are written onto it.


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find

Syntax

find pathname -name filename to be search -print

Used to search for files in a directory.

The parameters -name and -print are compulsory.

Example

To find a file A in the `/` i.e. root directory the command would be

$find / -name fileA -print


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In

Syntax

In file1 file2

Used to establish an additional filename for the same ordinaryfile.

In this file1 is the name of the ordinary file for which you wish

to establish an additional name or link and file2 is theadditional name of the file specified by file1.

It creates multiple links for the same file.

Example To create a link for a file `appeal`

$In appeal appeal1


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Is (contd.)

-r Reverse order of sort of listing

-R Recursively listing files of all subdirectories

-p Puts a slash(/) after each filename if that file is a directory.

-F Puts a slash(/) after each filename if that file is a directory and

puts a asterisk (*) after each filename if that filename is

executable.

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Is (contd.)

Examples

To list the files in the long format in the present directory.

$ ls l

total3

-rw -r--r-- 1 CMS student 13 Jan 1 10:39

data1

-rwxrwxrwx 1 CMS student 19 Feb 10 21:35

data2

drwxrwxr -- 2 CMS student 32 jan 16 16:50

prog-files

Revision no : PPT/2K605/03


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mkdir/md

Syntax

mkdir/md pathname

To create directories in your current directory.

Example

To create a directory `dd` in the present working directory

$mkdir dd



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more

Syntax

more [options] [file1 file2 file3 ............]

It allows the display of text in controlled increments on a CRT

terminal.

It is commonly used to make it possible to read the contents of

a long text file or the data stream in a pipe line a screen full at

a time.

Example

To list the entire contents of a large directory one screen at a time

$ls |more



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mv

Syntax

mv [option] file....... Target

It is used to move or rename files/directories.

Example

To rename the file named `wordlist` to `dictionary`.$mv wordlist dictionary

To move/rename two files `appeal` and `poem` respectively to the

Mail directory.$mv appeal poem Mail



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pwd

Syntax

Pwd

To display the full pathname for the current (or working)

directory.

Example If one is presently working in `/etc` directory the command would

give the resultas follows

$pwd/etc

$



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rmdir/rd

Syntax

rmdir/rd pathname

Used to delete a directory (directory should be empty before

deleting).

Example

To remove a directory `asdf` from the present working direcory

$rmdir asdf



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wc

Syntax

wc [options] file...

To count the lines, words and characters in one or more filesthat you specify on the command line.

Command switches with `wc` are:

-l to count the number of lines. -w to count the number of words.

-c to count the number of characters.

Example To check the number of lines in the file `test`

$wc l test



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rm

Syntax

rm [options] file..

Used to remove one or more files from a directory. Command switches with `rm` are:

-f force the removal of files that do not have write permission.

-R recursively delete the entire contents of the directory as well

as the directory file itself.

Example

To remove the file name `appeal` the command would be

$rm appeal To delete all the files in the directory Mail as well as the directory

Mail.

$rm -R Mail


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tail

Syntax

tail [options] file...

Used to view the end of a file and by default the last 10 lines of

the file are displayed.

The switch -n used to print the last n lines of the file mentioned

in the command.

Example

To display last 5 lines of `dd` file command would be

$tail 5 dd



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who

Syntax

Who

Used to display the names of all the users who are currentlylogged in.

Example

To display the users currently logged in$who

CMS1 tty02 Feb 2 10:30






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who am i

Syntax

who am I

Used to display the name of the current user.

Example

To display the name of the user currently logged in.$who am i

CMS tty02Feb 2 10:30

$



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Cal

Syntax cal [month][year]

Used to display the current calendar month but can be used to

display any month and year specified. Example

To display the current calendar month$cal

May 2004Su Mo Tu We Th Fr Sa

12 3 4 5 6 7 89 10 11 12 13 14 15

16 17 18 19 20 21 2223 24 25 26 27 28 29

30 31



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date

Syntax

Date

Used to display the current date and time.

Example

To display the current date

$ date

Fri May 21 11:30:05 IST 2004

$

08 unix commands

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