08 Unix Commands
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Transcript of 08 Unix Commands
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Revision no.: PPT/2K403/02Revision no.: PPT/2K605/03
UNIX Commands
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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
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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
CMS2 tty03 Feb 2 9:40
CMS3 tty01 Feb 2 9:00
CMS4 tty07 Feb 2 9:00
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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
$