78
Command A Command A alias COMMAND: alias command allows you to create a shortcut to a command. As the name indicates, you can set alias/shortcut name for the commands/paths which is too longer to remember. SYNTAX: The Syntax is alias [options] [ AliasName [ =String ] ] OPTIONS: -a Removes all alias definitions from the current shell execution environment. -p Prints the list of aliases in the form alias name=value on standard output. EXAMPLE: 1. To create a shortcut temporarily: alias lhost='cd /var/www/html' This command will set lhost to cd /var/www/html/. Now if you type lhost it will take you to the specified folder/directory. 2. To create a shortcut Permanently: You can put your aliases into the /home/user/.bashrc file. It is good to add them at the end of the file. alias home='cd /var/www/html/hscripts/linux-commands' Now if you type home it will take you to the specified folder/directory. 3. To create a shortcut for a command: alias c='clear' This command will set c to clear. Now if you type c it will clear the screen. awk COMMAND: awk command is used to manipulate the text.This command checks each line of a file, looking for patterns that match those given on the command line.

Linux & Unix Command

Embed Size (px)

Citation preview

Page 1: Linux & Unix Command

Command ACommand A

alias COMMAND:     alias command allows you to create a shortcut to a command. As the name indicates, you can set alias/shortcut name for the commands/paths which is too longer to remember.

SYNTAX:  The Syntax is      alias [options] [ AliasName [ =String ] ]

OPTIONS:     

-a Removes all alias definitions from the current shell execution environment.

-p Prints the list of aliases in the form alias name=value on standard output.

EXAMPLE:     

1. To create a shortcut temporarily:

alias lhost='cd /var/www/html'

This command will set lhost to cd /var/www/html/.Now if you type lhost it will take you to the specified folder/directory.

2. To create a shortcut Permanently:You can put your aliases into the /home/user/.bashrc file. It is good to add them at the end of the file.

alias home='cd /var/www/html/hscripts/linux-commands'

Now if you type home it will take you to the specified folder/directory.

3. To create a shortcut for a command:

alias c='clear'

This command will set c to clear.Now if you type c it will clear the screen.

awk COMMAND:     awk command is used to manipulate the text.This command checks each line of a file, looking for patterns that match those given on the command line.

SYNTAX:  The Syntax is      awk '{pattern + action}' {filenames}

OPTIONS:     

-W version Display version information and exit.

-F Print help message and exit.

Page 2: Linux & Unix Command

EXAMPLE:     Lets create a file file1.txt and let it have the following data:

Data in file1.txt

14   15   16

15   15   11

5     56    6

5     25    11. To print the second column data in file1.txt

awk '{print $2}' file1.txt

This command will manipulate and print second column of text file (file1.txt). The output will look like

15155625

2. To multiply the column-1 and column-2 and redirect the output to file2.txt:

awk '{print $1,$2,$1*$2}' file1.txt > file2.txtCommand Explanation:

$1 : Prints 1st column

$2 : Prints 2ndcolumn

$1*$2 : Prints Result of $1 x $2

file1.txt :  input file

> :  redirection symbol

file2.txt :  output fileThe above command will redirect the output to file2.txt and it will look like,14    15    21015    15    2255      56    2805      25    125

autoreconf COMMAND:     autoreconf - Update generated configuration files

Run 'autoreconf' repeatedly to remake the GNU Build System files in the DIRECTORIES or the directory trees driven by CONFIG-URE-AC.

     By default, it only remakes those files that are older than their predecessors. If you install new versions of the GNU Build System, running 'autoreconf' remakes all of the files by giving it the '--force' option.

SYNTAX:  The Syntax is       autoreconf [OPTION] ... [CONFIGURE-AC or DIRECTORY] ...

OPTIONS:     

Operation modes:

Page 3: Linux & Unix Command

-h,--help print this help, then exit.

-V, --version print version number, then exit.

-v,--verbose verbosely report processing.

-d,--debug don't remove temporary files.

-f, --force consider all files obsolete.

-i, --install copy missing auxiliary files.

-s,--symlink with -i, install symbolic links instead of copies

-m, --make when applicable, re-run ./configure && make

-W,--warnings=CATEGORY report the warnings falling in CATEGORY [syntax]

Warning categories include:

'cross' cross compilation issues

'gnu' GNU coding standards (default in gnu and gnits modes).

'obsolete' obsolete features or constructions

'override' user redefinitions of Automake rules or variables

'portability' portability issues

'syntax' dubious syntactic constructs (default).

EXAMPLE:     

autoreconf --force --install -I config -I m4a2p COMMAND:     a2p - Awk to Perl translatorA2p takes an awk script specified on the command line (or from standard input) and produces a comparable perl script on the standard output.

SYNTAX:  The Syntax is       a2p [options] [filename]

OPTIONS:     

-D<number> sets debugging flags.

-F<character> tells a2p that this awk script is always invoked with this -F switch.

-n<fieldlist>specifies the names of the input fields if input does not have to be split into an array.

-<number> causes a2p to assume that input will always have that many fields.

EXAMPLE:     

a2p myfile - would convert the file myfile.

Page 4: Linux & Unix Command

Awk to perl translator scripts are often embedded in a shell script that pipes stuff into and out

of awk. Often the shell script wrapper can be incorporated into the perl script, since perl can

start up pipes into and out of itself, and can do other things that awk can't do by itself. 

Command B

bc COMMAND:     bc command is used for command line calculator. It is similar to basic calculator. By using which we can do basic mathematical calculations.

SYNTAX:  The Syntax is      bc [options]

OPTIONS:     

-c Compile only. The output is dc commands that are sent to the standard output.

-l Define the math functions and initialize scale to 20, instead of the default zero.

filenameName of the file that contains the basic calculator commands to be calculated this is not a necessary command.

EXAMPLE:     

1. bc

Output:

bc 1.06Copyright 1991-1994,1997,1998,2000 Free Software Foundation,Inc.This is free software with ABSOLUTELY NO WARRANTY.For details type `warranty'.9*218

The above command used is for mathematical calculations.

2. bc -l

Output:

bc 1.06Copyright 1991-1994,1997,1998,2000 Free Software Foundation,Inc.This is free software with ABSOLUTELY NO WARRANTY.For details type `warranty'.1+23

The above command displays the sum of '1+2'.

3. bc calc.txt

Page 5: Linux & Unix Command

Output:

bc 1.06Copyright 1991-1994,1997,1998,2000 Free Software Foundation,Inc.This is free software with ABSOLUTELY NO WARRANTY.For details type `warranty'. 3

'calc.txt' file have the following code:1+2. Get the input from file and displays the output.

bg COMMAND:     bg command is used to place a job in background. User can run a job in the background by adding a "&" symbol at the end of the command.

SYNTAX:  The Syntax is      bg [options] [job]

OPTIONS:     

-l Report the process group ID and working directory of the jobs.

-p Report only the process group ID of the jobs.

-xReplace any job_id found in command or arguments with the corresponding process group ID, then execute command passing it arguments.

job Specifies the job that want to run in the background.

EXAMPLE:     

1. To Run a process in background2. kmail- start the email client application.

Press ctrl+z to stop the current job.

Now just type bg to move last stopped job to background.

3. To move the specified job to back ground:

Lets start some three jobs and suspend those process in background.

kmail- start the email client application.

Press ctrl+z to stop the current job.

xmms- music player application.

Press ctrl+z to stop the current job.

sleep 120- a dummy job.

Press ctrl+z to stop the current job.

Page 6: Linux & Unix Command

jobs

The above command will display the jobs in the shell.

[1] Stopped kmail[2]- Stopped xmms[3]+ Stopped sleep 120bg 2

The above command will start running the xmms application. In such way you can start running the specific background process.

jobs[1]- Stopped kmail[2] Running xmms &[3]+ Stopped sleep 120

bzip2 COMMAND:     bzip2 linux command is used to compress the file. Each file is replaced by a compressed version of itself with .bz2 extension.

SYNTAX:  The Syntax is      bzip2 [ options ] filenames

OPTIONS:     

- c Compress or decompress to standard output.

- d Force decompression.

- z The complement to -d. Force compression.

- tPerforms the integrity test. It performs a trial decompression test and prints the result.

- f Force overwrite of output file.

- kKeep the original file. dont delete the input file during compression or decompression.

- q Quiet, suppress non-essential warning messages.

- s Reduce memory usage, for compression,decompression and testing.

- v verbose mode shows the compression ratio for each file processed.

- V Displays the version of the software.

- L Displays the license terms and conditions.

- 1 Performs fast compression,creating a relatively large files.

- 9 Get the best possible compression.

EXAMPLE:     

1. To Compress a file using bzip2:

Lets have a text file as an example.

Page 7: Linux & Unix Command

$ ls -l-rw-rw-r-- 1 hiox hiox 9150000 Sep 26 18:37 hiox.txt

$ bzip2 -c -1 hiox.txt > hiox.txt.bz2$ ls -l-rw-rw-r-- 1 hiox hiox 9150000 Sep 26 18:37 hiox.txt-rw-rw-r-- 1 hiox hiox 17706 Sep 27 12:38 hiox.txt.bz2

From the above example it is clear that the filesize is reduced from 9150000 bytes to 17706.

When the File is reduced with option -9 the filesize still gets reduced.

$ bzip2 -c -9 hiox.txt > hscripts.txt.bz2

$ ls -l-rw-rw-r-- 1 hiox hiox 9150000 Sep 26 18:37 hiox.txt-rw-rw-r-- 1 hiox hiox 17706 Sep 27 12:38 hiox.txt.bz2-rw-rw-r-- 1 hiox hiox 2394 Sep 27 13:01 hscripts.txt.bz2

When the file is compressed with -1 the size was 17706 bytes and now the filesize is 2394 bytes. The 9 makes best compression but the default is 6.

Command ccal COMMAND:     cal command is used to display the calendar.

SYNTAX:  The Syntax is      cal [options] [month] [year]

OPTIONS:     

-1 Displays single month as output.

-3 Displays prev/current/next month output.

-s Displays sunday as the first day of the week.

-m Displays Monday as the first day of the week.

-j Displays Julian dates (days one-based, numbered from January 1).

-y Displays a calendar for the current year.

EXAMPLE:     

1. cal 

Output:

September 2008 Su Mo Tu We Th Fr Sa 1 2 3 4 5 6 7 8 9 10 11 12 1314 15 16 17 18 19 2021 22 23 24 25 26 27

Page 8: Linux & Unix Command

28 29 30

cal command displays the current month calendar.

2. cal -3 5 2008

Output:

April 2008 May 2008 June 2008 Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa 1 2 3 4 5 1 2 3 1 2 3 4 5 6 7 6 7 8 9 10 11 12 4 5 6 7 8 9 10 8 9 10 11 12 13 1413 14 15 16 17 18 19 11 12 13 14 15 16 17 15 16 17 18 19 20 2120 21 22 23 24 25 26 18 19 20 21 22 23 24 22 23 24 25 26 27 2827 28 29 30 25 26 27 28 29 30 31 29 30

Here the cal command displays the calendar of April, May and June month of year 2008.

cat COMMAND:     cat linux command concatenates files and print it on the standard output.

SYNTAX:  The Syntax is      cat [OPTIONS] [FILE]...

OPTIONS:     

-A Show all.

-b Omits line numbers for blank space in the output.

-e A $ character will be printed at the end of each line prior to a new line.

-E Displays a $ (dollar sign) at the end of each line.

-n Line numbers for all the output lines.

-s If the output has multiple empty lines it replaces it with one empty line.

-T Displays the tab characters in the output.

-vNon-printing characters (with the exception of tabs, new-lines and form-feeds) are printed visibly.

EXAMPLE:     

1. To Create a new file:

cat > file1.txt

This command creates a new file file1.txt. After typing into the file press control+d (^d) simultaneously to end the file.

2. To Append data into the file:

cat >> file1.txt

Page 9: Linux & Unix Command

To append data into the same file use append operator >> to write into the file, else the file will be overwritten (i.e., all of its contents will be erased).

3. To display a file:

cat file1.txt

This command displays the data in the file.

4. To concatenate several files and display:

cat file1.txt file2.txt

The above cat command will concatenate the two files (file1.txt and file2.txt) and it will display the output in the screen. Some times the output may not fit the monitor screen. In such situation you can print those files in a new file or display the file using less command.

cat file1.txt file2.txt | less

5. To concatenate several files and to transfer the output to another file.

cat file1.txt file2.txt > file3.txt

In the above example the output is redirected to new file file3.txt. The cat command will create new file file3.txt and store the concatenated output into file3.txt.

cd COMMAND:     cd command is used to change the directory.

SYNTAX:  The Syntax is      cd [directory | ~ | ./ | ../ | - ]

OPTIONS:     

-L Use the physical directory structure.

-P Forces symbolic links.

EXAMPLE:     

1. cd linux-command

This command will take you to the sub-directory(linux-command) from its parent directory.

2. cd ..

This will change to the parent-directory from the current working directory/sub-directory.

3. cd ~

This command will move to the user's home directory which is "/home/username".

Page 10: Linux & Unix Command

chattr COMMAND:     chattr command is used to change the file attributes. This is an admin command. Root user only can change the file attributes/Process.

SYNTAX:  The Syntax is      chattr [options] filename

OPTIONS:     

+i Make the file as Read-Only.

-i Remove the Read-Only.

+a Can't open file for writing.

-a Open file for writing.

+S The changes in the file are written synchronously on the disk.

EXAMPLE:     

1. chattr +i test.txt

Here the 'test.txt' file has the write permission, to make it as Read-Only file use +i option.

2. chattr -i test.txt

The above command process is used to remove the Read-Only mark.

chgrp COMMAND:     chgrp command is used to change the group of the file or directory. This is an admin command. Root user only can change the group of the file or directory.

SYNTAX:  The Syntax is      chgrp [options] newgroup filename/directoryname

OPTIONS:     

-RChange the permission on files that are in the subdirectories of the directory that you are currently in.

-c Change the permission for each file.

-f Force. Do not report errors.

EXAMPLE:     

1. chgrp hiox test.txt

The group of 'test.txt' file is root, Change to newgroup hiox.

2. chgrp -R hiox test

The group of 'test' directory is root. With -R, the files and its subdirectories also changes to newgroup hiox.

Page 11: Linux & Unix Command

3. chgrp -c hiox calc.txt

They above command is used to change the group for the specific file('calc.txt') only.

chkconfig COMMAND:     chkconfig command is used to change, update and query runlevel information for system services. chkconfig is an admin command.

SYNTAX:  The Syntax is      chkconfig [options]

OPTIONS:     

--add serviceCreate a start or kill symbolic link in every runlevel for the specified service according to default behavior specified in the service's initialization script.

--listPrint whether the specified service is on or off in each level. If no service is specified, print runlevel information for all services managed by chkconfig.

--level numbersSpecify by number the runlevels to change. Provide numbers as a numeric string: e.g., 016 for levels 0, 1 and 6. Use this to override specified defaults.

--del service Remove entries for specified service from all runlevels.

EXAMPLE:     

1. chkconfig --list

The above configuration command list the runlevels and the service status(i.e, on or off).

2. chkconfig tomcat5 off

The above command is used to set the status for tomcat5 service. Now tomcat5 service status is off.

3. chkconfig --list tomcat5

Output:

tomcat5 0:off 1:off 2:off 3:off 4:off 5:off 6:off

The above command displays the status of tomcat5 service(i.e, on or off).

Explanation

chmod COMMAND:     chmod command allows you to alter / Change access rights to files and directories.

File Permission is given for users,group and others as,

Read Write Execute

Page 12: Linux & Unix Command

User

Group

Others

Permission

Symbolic Mode

SYNTAX:  The Syntax is      chmod [options] [MODE] FileName

File Permission

# File Permission

0 none

1 execute only

2 write only

3 write and execute

4 read only

5 read and execute

6 read and write

7 set all permissions

OPTIONS:     

-c Displays names of only those files whose permissions are being changed

-f Suppress most error messages

-R Change files and directories recursively

-v Output version information and exit.

EXAMPLE:     

1. To view your files with what permission they are:

ls -alt

This command is used to view your files with what permission they are.

2. To make a file readable and writable by the group and others.

chmod 066 file1.txt

000

___ ___ ___

Page 13: Linux & Unix Command

3. To allow everyone to read, write, and execute the file

chmod 777 file1.txtchown COMMAND:     chown command is used to change the owner / user of the file or directory. This is an admin command, root user only can change the owner of a file or directory.

SYNTAX:  The Syntax is      chown [options] newowner filename/directoryname

OPTIONS:     

-RChange the permission on files that are in the subdirectories of the directory that you are currently in.

-c Change the permission for each file.

-fPrevents chown from displaying error messages when it is unable to change the ownership of a file.

EXAMPLE:     

1. chown hiox test.txt

The owner of the 'test.txt' file is root, Change to new user hiox.

2. chown -R hiox test

The owner of the 'test' directory is root, With -R option the files and subdirectories user also gets changed.

3. chown -c hiox calc.txt

Here change the owner for the specific 'calc.txt' file only.

Explanation

chpasswd COMMAND:     chpasswd command is used to change password for users. This is an admin command, Only root user can change the password for users.

SYNTAX:  The Syntax is      chpasswd [options]

OPTIONS:     

-c Clears all password flags.

-e Specifies that the passwords are of encrypted format.

-f flagsSpecifies the comma separated list of password flags to set. Valid flag values are: ADMIN, ADMCHG, and/or NOCHECK. Refer to the pwdadm command documentation for details about these values.

Page 14: Linux & Unix Command

-R load_module Specifies the loadable I & A module used to change user's password.

EXAMPLE:     

1. To reset password for users from command line,type

chpasswd

Followed by entering username:password pairs, one pair per line. Enter ctrl+D when finished.

user1:passwd1 user2:passwd2 ....

Explanation

clear COMMAND:     This command clears the terminal screen.

SYNTAX:  The Syntax is      clear

OPTIONS:     There is no options for clearscreen command.

EXAMPLE:     

1. clearclear command clearscreen like cls command.

2. You can also have alias for this command.

alias c='clear'c is the alias name for clear command.

cmp COMMAND:     cmp linux command compares two files and tells you which line numbers are different.

SYNTAX:  The Syntax is      cmp [options..] file1 file2

OPTIONS:     

- c Output differing bytes as characters.

- lPrint the byte number (decimal) and the differing byte values (octal) for each difference.

- s Prints nothing for differing files, return exit status only.

EXAMPLE:     

Page 15: Linux & Unix Command

1. Compare two files:

cmp file1 file2

The above cmp command compares file1.php with file2.php and results as follows.

file1.php file2.php differ: byte 35, line 3

2. Compare two files output differing bytes as characters:

cmp -c file1.php file2.php

The above cmp command compares file1.php with file2.php and results as follows.

file1.php file2.php differ: byte 35, line 3 is 151 i 15

cp COMMAND:     cp command copy files from one location to another. If the destination is an existing file, then the file is overwritten; if the destination is an existing directory, the file is copied into the directory (the directory is not overwritten).

SYNTAX:  The Syntax is      cp [OPTIONS]... SOURCE DEST     cp [OPTIONS]... SOURCE... DIRECTORY     cp [OPTIONS]... --target-directory=DIRECTORY SOURCE... 

OPTIONS:     

-a same as -dpR.

--backup[=CONTROL] make a backup of each existing destination file

-b like --backup but does not accept an argument.

-f if an existing destination file cannot be opened, remove it and try again.

-p same as --preserve=mode,ownership,timestamps.

--preserve[=ATTR_LIST]

preserve the specified attributes (default: mode,ownership,timestamps) and security contexts, if possible additional attributes: links, all.

--no-preserve=ATTR_LIST

don't preserve the specified attribute.

--parents append source path to DIRECTORY.

EXAMPLE:     

1. Copy two files:

cp file1 file2

The above cp command copies the content of file1.php to file2.php.

Page 16: Linux & Unix Command

2. To backup the copied file:

cp -b file1.php file2.php

Backup of file1.php will be created with '~' symbol as file2.php~.

3. Copy folder and subfolders:

cp -R scripts scripts1

The above cp command copy the folder and subfolders from scripts to scripts1.

cpio COMMAND:     cpio command creates and un-creates archived cpio files. It is capable of copying files to things other than a hard disk. Probably, this command is also used to backup and restore files.

SYNTAX:  The Syntax is      cpio [options]

OPTIONS:     

-i Extracts files from the standard input.

-oReads the standard input to obtain a list of path names and copies those files onto the standard output.

-p Reads the standard input to obtain a list of path names of files.

-c Read or write header information in ASCII character form for portability.

-d Creates directories as needed.

-uCopy unconditionally (normally, an older file will not replace a newer file with the same name).

-mRetain previous file modification time. This option is ineffective on directories that are being copied.

-v Verbose.Print a list of file names.

EXAMPLE:     

1. find . -print | cpio -ocv > /dev/fd0

Find list of files and directories and then copy those to floppy drive.

2. find . -print | cpio -dumpv /home/nirmala

Find list of files and directories and then copy or backup those to user.

3. cpio -icuvd < /dev/fd0

Restore the files back from the floppy.

Page 17: Linux & Unix Command

cut COMMAND:     cut command is used to cut out selected fields of each line of a file. The cut command uses delimiters to determine where to split fields.

SYNTAX:  The Syntax is      cut [options]

OPTIONS:     

-c Specifies character positions.

-b Specifies byte positions.

-d flags Specifies the delimiters and fields.

EXAMPLE:     Lets create a file file1.txt and let it have the following data:

Data in file1.txt

This is, an example program,for cut command.1. cut -c1-3 text.txt

Output:

Thi

Cut the first three letters from the above line.

2. cut -d, -f1,2 text.txt

Output:

This is, an example program

The above command is used to split the fields using delimiter and cut the first two fields.

Command D

Explanation

date COMMAND:     date command prints the date and time.

SYNTAX:  The Syntax is      date  [options] [+format] [date]

OPTIONS:     

-aSlowly adjust the time by sss.fff seconds (fff represents fractions of a second). This adjustment can be positive or negative.Only system admin/ super user can adjust the time.

Page 18: Linux & Unix Command

-s date-string

Sets the time and date to the value specfied in the datestring. The datestr may contain the month names, timezones, 'am', 'pm', etc.

-u Display (or set) the date in Greenwich Mean Time (GMT-universal time).

Format:

%a Abbreviated weekday(Tue).

%A Full weekday(Tuesday).

%b Abbreviated month name(Jan).

%B Full month name(January).

%c Country-specific date and time format..

%D Date in the format %m/%d/%y.

%j Julian day of year (001-366).

%n Insert a new line.

%p String to indicate a.m. or p.m.

%T Time in the format %H:%M:%S.

%t Tab space.

%V Week number in year (01-52); start week on Monday.

EXAMPLE:     

1. date command 

date

The above command will print Wed Jul 23 10:52:34 IST 2008

2. To use tab space:

date +"Date is %D %t Time is %T"

The above command will remove space and print asDate is 07/23/08 Time is 10:52:34

3. To know the week number of the year,

date -V

The above command will print 30

Page 19: Linux & Unix Command

4. To set the date,

date -s "10/08/2008 11:37:23"

The above command will print Wed Oct 08 11:37:23 IST 2008Explanation

dd COMMAND:     dd command is used to dump the data. The data in a file or device or partition can be dumped to another file or device or partition. This command is also used for creating bootable devices.

SYNTAX:  The Syntax is      dd [options]

OPTIONS:     

-ifSpecifies the input device or partition (or) file from which data is to be dumped

-ofSpecifies the output device or partition (or) file to which data is to be dumped

-ibsSpecifies how many bytes is to be readed from a input file at a time during the dumping process

-obsSpecifies how many bytes is to be written to the output file at a time during the dumping process

-bsSpecifies how many bytes is to be readed and written at a time during the dumping process

-count=[bytes]

Specifies how many bytes is to be dumped from 'if' to 'of'

EXAMPLE:     

1. To create bootable floppy :

dd if=diskboot.img of=/dev/fd0This command creates the bootable floppy.

In above command:diskboot.img -Is the bootable image/dev/fd0 -Is a floppy disk

2. To import the data from one hard-disk to another hard-disk:

dd if=/dev/sda of=/dev/sdbIn above command:/dev/sda -Is the hard-disk from which data is dumped/dev/sdb -Is the hard-disk to which data is dumped

3. To import the data from one partition to another partition:

dd if=/dev/sda1 of=/dev/sda2/dev/sda1 -Is the partition from which data is dumped/dev/sda2 -Is the partition to which data in /dev/sda1 is dumped

Page 20: Linux & Unix Command

4. To Specify number of bytes readed and written at a time during dumping:

dd if=/dev/sda1 of=/dev/sda2 bs=2100The above command will dump data from /dev/sda1 to /dev/sda2 by reading and writing 2100 bytes at a time.

df COMMAND:     df command is used to report how much free disk space is available for each mount you have. The first column show the name of the disk partition as it appears in the /dev directory. Subsequent columns show total space, blocks allocated and blocks available.

SYNTAX:  The Syntax is      df [options]

OPTIONS:     

-a Include dummy file systems.

-h Print sizes in human readable format.(e.g., 1K 234M 2G)

-H Print sizes in human readable format but use powers of 1000 not 1024.

-i List inode information instead of block usage.

-l Limit listing to local file systems.

-P Use the POSIX output format.

-T Print file system type.

EXAMPLE:     

1. df

Output:

Filesystem 1K-blocks Used Available Use% Mounted on/dev/mapper/VolGroup00-LogVol00 150263916 14440324 128067408 11% //dev/sda1 101086 10896 84971 12% /boottmpfs 253336 0 253336 0% /dev/shm

In the above output: /dev/mapper/VolGroup00-LogVol00 -> Specifies FileSystem. /dev/sda1 -> Specifies FileSystem. tmpfs -> Specifies FileSystem.

Prints default format.

2. df -h

Output:

Filesystem Size Used Avail Use% Mounted on/dev/mapper/VolGroup00-LogVol00 144G 14G 123G 11% /

Page 21: Linux & Unix Command

/dev/sda1 99M 11M 83M 12% /boottmpfs 248M 0 248M 0% /dev/shm

Print size in human readable format.

3. df -H

Output:

Filesystem Size Used Avail Use% Mounted on/dev/mapper/VolGroup00-LogVol00 154G 15G 132G 11% //dev/sda1 104M 12M 88M 12% /boottmpfs 260M 0 260M 0% /dev/shm

Print size in human readable format but use powers of 1000 not to 1024.

diff COMMAND:     diff command is used to find differences between two files.

SYNTAX:  The Syntax is      diff [options..] from-file to-file

OPTIONS:     

-a Treat all files as text and compare them line-by-line.

-b Ignore changes in amount of white space.

-c Use the context output format.

-e Make output that is a valid ed script.

-HUse heuristics to speed handling of large files that have numerous scattered small changes.

-i Ignore changes in case; consider upper- and lower-case letters equivalent.

-nPrints in RCS-format, like -f except that each command specifies the number of lines affected.

-qOutput RCS-format diffs; like -f except that each command specifies the number of lines affected.

-r When comparing directories, recursively compare any subdirectories found.

-s Report when two files are the same.

-w Ignore white space when comparing lines.

-y Use the side by side output format.

EXAMPLE:     

Lets create two files file1.txt and file2.txt and let it have the following data.

Data in file1.txt Data in file2.txt

Page 22: Linux & Unix Command

HIOX TESThscripts.comwith friend shiphiox india

HIOX TESTHSCRIPTS.comwith   friend    ship

1. Compare files ignoring white space:

diff -w file1.txt file2.txt

This command will compare the file file1.txt with file2.txt ignoring white/blank space and it will produce the following output.

2c2< hscripts.com---> HSCRIPTS.com4d3< Hioxindia.com

2. Compare the files side by side, ignoring white space:

diff -by file1.txt file2.txt

This command will compare the files ignoring white/blank space, It is easier to differentiate the files.

HIOX TEST HIOX TESThscripts.com | HSCRIPTS.comwith friend ship with friend shipHioxindia.com <

The third line(with friend ship) in file2.txt has more blank spaces, but still the -b ignores the blank space and does not show changes in the particular line, -y printout the result side by side.

3. Compare the files ignoring case.

diff -iy file1.txt file2.txt

This command will compare the files ignoring case(upper-case and lower-case) and displays the following output.

HIOX TEST HIOX TESThscripts.com HSCRIPTS.comwith friend ship | with friend shipHioxindia.com <

du COMMAND:     du command is used to report how much disk space a file or directory occupies.

Page 23: Linux & Unix Command

SYNTAX:  The Syntax is      du [options] directories

OPTIONS:     

-a Displays the usage of space that each file is taking up.

-k Write the files size in units of 1024 bytes, rather than the default 512-byte units.

-s Instead of the default output, report only the total sum for each of the specified files.

-LProcess symbolic links by using the file or directory which the symbolic link references, rather than the link itself.

-xWhen evaluating file sizes, evaluate only those files that have the same device as the file specified by the file operand.

EXAMPLE:     

1. du -a images

Output:

12 images/daisy.jpg20 images/flo.gif76 images/CHILD.gif12 images/indigo.gif152 images/flower.gif12 images/sunflower.jpg12 images/tulip-flower-clipart5.gif12 images/flower.jpg8 images/thumbnail.aspx8 images/baby.jpg12 images/woodpecker.gif168 images/baby.gif8 images/thumbnail.jpg1012 images/house.bmp12 images/peacock.gif1544 images

Displays the size of each file in the specified directory.

2. du -s images

Output:

1544 images

Displays the total disk space used by the specified directory.

3. du -h

Output:

84K

Page 24: Linux & Unix Command

Displays the current folder capacity.

4. du -h file1.php

Output:

8.0K file1.php

Displays the storage capacity of file1.php.

dump COMMAND:     dump command makes backup of filesystem or file and directories.

SYNTAX:  The Syntax is      dump [options] [dump-file] [File-system or file or directories].

OPTIONS:     

-[level] The dump level any integer

-f Make the backup in a specified file

-u Updates /etc/dumpdats file for the backup made

-v Displays Verbose Information

-e Exclude inode while making backup

EXAMPLE:     

1. To make a backup for a directory or file :

dump -0uf databackup /home/user1/data

This command creates a dump-file called databackup which is the backup of /home/user1/data directory.

In above command:-0 -Is the dump-level [0 specifies full-backup]databackup -Is a dump-file [or backup-file]/home/user1/data -Is a directory for which a backup is created

2. To make a backup for a directory or file which is already backedup with dump level 0:

dump -1uf databackup /home/user1/data

This command backups all the new files added to /home/user1/data directory after level-0 dump is made.

-1 -Is the dump-level [1 specifies incremental backup]databackup -Is a dump-file [or backup-file]/home/user1/data -Is a directory for which a backup is created

Page 25: Linux & Unix Command

echo COMMAND:     echo command prints the given input string to standard output.

SYNTAX:  The Syntax is      echo [options..] [string]

OPTIONS:     

-n do not output the trailing newline

-e enable interpretation of the backslash-escaped characters listed below

-E disable interpretation of those sequences in STRINGs

    Without -E, the following sequences are recognized and interpolated:

\NNN the character whose ASCII code is NNN (octal)

\a alert (BEL)

\\ backslash

\b backspace

\c suppress trailing newline

\f form feed

\n new line

\r carriage return

\t horizontal tab

\v vertical tab

EXAMPLE:     

1. echo command 

echo "hscripts Hiox India"

The above command will print as hscripts Hiox India

2. To use backspace:

echo -e "hscripts \bHiox \bIndia"

The above command will remove space and print as hscriptsHioxIndia

3. To use tab space in echo command

echo -e "hscripts\tHiox\tIndia"

The above command will print as hscripts          Hiox          India

Command ECommand E

Page 26: Linux & Unix Command

egrep COMMAND:     egrep command is used to search and find one or more files for lines that match the given string or word.

SYNTAX:  The Syntax is      egrep [options] pattern [file]

OPTIONS:     

-b Print the byte offset of input file before each line of output.

-c Print's the count of line matched.

-e  pattern list Searches the pattern list.

-h Print matched lines but not filenames.

-i Ignore changes in case; consider upper- and lower-case letters equivalent.

-n Print line and line number.

-q Prints in quite mode, prints nothing.

-r Recursively read all files in directories and in subdirectories found.

-v Prints all the lines that do not match.

-V Print Version.

-w Match on whole word only.

You can also use Patterns for search operation.

. Matches single character.

* Wild Character.

^ Starting with.

$ Ending with.

EXAMPLE:      Lets assume that we have a file file1.txt and it has the following data.

hscripts has many valuable free scriptsIt is the parent site of www.forums.hscripts.comhscripts include free tutorials and free gif imagesfree DNS lookup toolPurchase scripts from usA webmaster/web master resource website

1. To search more words from a file :

egrep 'hscripts|forums|free' file1.txt

The output will be.hscripts has many valuable free scriptsIt is the parent site of www.forums.hscripts.comhscripts include free tutorials and free gif imagesfree DNS lookup tool

2. To print the lines containing "free" followed by images:

Page 27: Linux & Unix Command

egrep 'free.*images' file1.txt

The output will be.hscripts include free tutorials and free gif images

Command FCommand F

fdisk COMMAND:     fdisk command is used for partition table manipulator. Hard disks can be divided into one or more logical disks called partitions.

SYNTAX:  The Syntax is      fdisk [options]

OPTIONS:     

-l List the partition tables for the specified devies and then exit.

-u When listing partition tables, give sizes in sectors instead of cylinders.

-s The size of the partition is printed on the standard output.

-b Specify the sector size of the disk.

-C Specify the number of cylinders of the disk.

-H Specify the number of heads of the disk.

-S Specify the number of sectors per track of the disk.

EXAMPLE:     

1. fdisk /dev/hdb

It prints the partition table and configuration information.

Explanation

fg COMMAND:     fg command is used to place a job in foreground.

SYNTAX:  The Syntax is      fg [specify job]

OPTIONS:     There is no options for fg command.

EXAMPLE:     

1. To move a process in foreground:

Lets start some three jobs and suspend those running process in background.

kmail- start the email client application.

Page 28: Linux & Unix Command

Press ctrl+z to stop the current job.

xmms- music player application.

Press ctrl+z to stop the current job.

sleep 120- a dummy job.

Press ctrl+z to stop the current job.

jobs

The above command will display the jobs in the shell.

[1] Stopped kmail[2]- Stopped xmms[3]+ Stopped sleep 120fg 1

The above command will run the kmail application process in foreground.fgrep COMMAND:     fgrep command is used to search one or more files for lines that match the given string or word. fgrep is faster than grep search, but less flexible: it can only find fixed text, not regular expressions.

SYNTAX:  The Syntax is      fgrep [options] pattern [file]

OPTIONS:     

-a Don't suppress output lines with binary data, treat as text.

-b Print the byte offset of input file before each line of output.

-c Print's the count of line matched.

-h Print matched lines but not filenames.

-i Ignore changes in case; consider upper- and lower-case letters equivalent.

-n Print line and line number.

-q Prints in quite mode, prints nothing.

-r Recursively read all files in directories and in subdirectories found.

-v Prints all the lines that do not match.

-V Print Version.

-w Match on whole word only.

EXAMPLE:      Lets assume that we have a file file1.txt and it has the following data.

hscripts is the parent site of www.forums.hscripts.comask your technical doubts in our forumour forums is free

1. To search and print the lines containing forum :

Page 29: Linux & Unix Command

fgrep 'forum' file1.txt

fgrep command prints the output as.hscripts is the parent site of www.forums.hscripts.comour forums is free

Explanation

file COMMAND:     file command tells you if the object you are looking at is a file or a directory.

SYNTAX:  The Syntax is      file [options] directoryname/filename

OPTIONS:     

-cCheck the magic file for format errors. For reasons of efficiency, this validation is normally not carried out.

-h Do not follow symbolic links.

-m Use mfile as an alternate magic file.

-f ffile contains a list of the files to be examined.

EXAMPLE:     

1. file *.txt

Output:

aprlist.txt: ASCII English textcal.txt: ASCII textmarchlist.txt: ASCII English texttext.txt: ASCII text

Prints the 'txt' files.

2. file nimi

Output:

nimi: directory

Print the given object nimi is an directory or file.Explanation

find COMMAND:     find command finds one or more files assuming that you know their approximate filenames.

SYNTAX:  The Syntax is      find path [options]

OPTIONS:

Page 30: Linux & Unix Command

     

-nameIt search for the given file, in the current directory or any other subdirectory.

-atime nTrue if the file was accessed n days ago. The access time of directories in path is changed by find itself.

-ctime n True if the file's status was changed n days ago.

-group gnameTrue if the file belongs to the group gname. If gname is numeric and does not appear in the /etc/group file, it is taken as a group ID.

-mtime n True if the file's data was modified n days ago.

-size n[c]True if the file is n blocks long (512 bytes per block). If n is followed by a c, the size is in bytes.

EXAMPLE:     

1. find -name 'cal.txt'The system would search for any file named 'cal.txt' in the current directory and any subdirectory.

2. find / -name 'cal.txt'The system would search for any file named 'cal.txt' on the root and all subdirectories from the root.

3. find -name '*' -size +1000kThe system would search for any file in the list that is larger than 1000k.Explanation

finger COMMAND:      finger command displays the user's login name, real name, terminal name and write status (as a ''*'' after the terminal name if write permission is denied), idle time, login time, office location and office phone number..

SYNTAX:  The Syntax is      finger [-lmsp] [user ...] [user@host ...]

OPTIONS:     

- lPrints all the information described by -s option and also the user's home directory, home phone number, login shell, mail status, and the contents of the files ".plan",".project",".pgpkey", and ".forward" from the users home directory.

- m Match arguments only on user name (not first or last name).

- pSupress the prinitng format of -l, It will not display the contents of ".plan",".project", and ".pgkey" files.

- s Prints the output in short format.

EXAMPLE:     

1. To Print the user information in short format:2. finger -s hiox

3. Login Name Tty Idle LoginTime Office OfficePhone4. HIOX HIOX INDIA *:0 Sep 14 09:07

Page 31: Linux & Unix Command

5. HIOX HIOX INDIA *pts/0 9 Sep 14 09:086. HIOX HIOX INDIA *pts/1 1:29 Sep 14 09:12

finger command prints the user information as user's login name, real name, terminal name and write status, idle time, login time, office location and office phone number.Explanation

free COMMAND:     free command displays information about free and used memory on the system.

SYNTAX:  The Syntax is      free [options] [-V]

OPTIONS:     

- b Prints the memory information in bytes.

- k Prints the memory information in kilo-bytes.

- m Prints the memory information in mega-bytes.

- s delay

Prints the output continously. Type the delay time to print the output continously.

- t prints a line containing totals.

EXAMPLE:     

1. To Print the memory size information:2. free

3. total used free shared buffers cached4. Mem: 223740 219492 4248 0 3756 732125. -/+ buffers/cache: 142524 812166. Swap: 1052216 66732 985484

The free command displays all the memory information of the system like total memory used and free memory.

7. To Print memory information from file:8. cat /proc/meminfo

9. MemTotal: 223740 kB10. MemFree: 8512 kB11. Buffers: 4432 kB12. Cached: 67860 kB13. SwapCached: 15032 kB14. Active: 172484 kB15. Inactive: 20168 kB16. HighTotal: 0 kB17. HighFree: 0 kB18. LowTotal: 223740 kB19. LowFree: 8512 kB20. SwapTotal: 1052216 kB21. SwapFree: 985488 kB22. Dirty: 52 kB23. Writeback: 0 kB24. Mapped: 166064 kB25. Slab: 14860 kB26. Committed_AS: 541000 kB

Page 32: Linux & Unix Command

27. PageTables: 3260 kB28. VmallocTotal: 794616 kB29. VmallocUsed: 3056 kB30. VmallocChunk: 791084 kB31. HugePages_Total: 032. HugePages_Free: 033. Hugepagesize: 4096 kB

The above command prints the memory information of the system.Explanation

Command GCommand G

grep COMMAND:     grep command selects and prints the lines from a file which matches a given string or pattern.

SYNTAX:  The Syntax is      grep [options] pattern [file]

OPTIONS:     

-A Print num lines of text that occur after the matching line.

-a Don't suppress output lines with binary data, treat as text.

-b Print the byte offset of input file before each line of output.

-c Print's the count of line matched.

-d action

Define action for accessing the directoriesread  read all files in the directories.skip  skip directories.recurse  recursively read all files and directories

-e pattern Search for pattern.

-h Print matched lines but not filenames.

-i Ignore changes in case; consider upper- and lower-case letters equivalent.

-n Print line and line number.

-q Prints in quite mode, prints nothing.

-r Recursively read all files in directories and in subdirectories found.

-v Prints all the lines that do not match.

-V Print Version.

-w Match on whole word only.

You can also use Patterns for search operation.

. Matches single character.

* Wild Character.

^ Starting with.

$ Ending with.

EXAMPLE:      Lets assume that we have a file file1.txt and it has the following data.

Page 33: Linux & Unix Command

hscripts has many valuable free scriptsIt is the parent site of www.forums.hscripts.comhscripts include free tutorials and free gif imagesPurchase scripts from usA webmaster/web master resource website1. To print all lines containing hscripts :

grep 'hscripts' file1.txtThe output will be.hscripts has many valuable free scriptsIt is the parent site of www.forums.hscripts.comhscripts include free tutorials and free gif images

2. To print the count of line that matches hscripts.

grep -c 'hscripts' file1.txtThe output will be.3

3. To print the lines that starts as hscripts.

grep '^hscripts' file1.txtThe output will be.hscripts has many valuable free scriptshscripts include free tutorials and free gif images

4. To Search the files in HEC directory which has the string "include":

grep -c 'include' HEC/*The above command will print the file name and count of line that matched the string "include"Sample output:HEC/admin.php:3HEC/auth.php:1HEC/calendar.php:3HEC/checklogin.php:0HEC/colors.php:0HEC/msize.php:3Explanation

groupadd COMMAND:     groupadd command is used to create a new group account.This is an admin command.

SYNTAX:  The Syntax is      groupadd [options] groupname

OPTIONS:     

-gThe numerical value of the group's ID. This value must be unique.Values between 0 and 99 are typically reserved for system accounts.

-rThis flag instructs groupadd to add a system account.This option is suitable for Redhat linux only.

Page 34: Linux & Unix Command

EXAMPLE:     

1. groupadd hioxindiaCreate a newgroup named as hioxindia.Explanation

groupdel COMMAND:     groupdel command is used to delete(remove) a group. This is an admin command.

SYNTAX:  The Syntax is      groupdel groupname

OPTIONS:     There is no options for groupdel command. Directly give the groupname.

EXAMPLE:     

1. groupdel hioxDelete(Remove) the group hiox.Explanation

groupmod COMMAND:     groupmod command is used to modify group. This is an admin command.

SYNTAX:  The Syntax is      groupmod [options] newname oldname

OPTIONS:     

-gThe numerical value of the group's ID. This value must be unique.Values between 0 and 99 are typically reserved for system accounts.The value must be non-negative.

-n The name of the group will be changed from group to group.

EXAMPLE:     

1. groupmod -n vizhi vizhi1In the above example the groupmod command would change the group 'vizhi' to 'vizhi1'.Explanation

groups COMMAND:     groups command is used to print the groups a user is in.

SYNTAX:  The Syntax is      groups

OPTIONS:     

--help Print help message and exit

--version

Print version and exit

Page 35: Linux & Unix Command

EXAMPLE:     

1. Prints the groups of user.

$ groupsOutput:hiox apache

2. Prints the groups of super user.

# groupsOutput:root bin daemon sys adm disk wheel.

Command HCommand H

Explanation

halt COMMAND:     halt command is used to shutdown the computer.

SYNTAX:  The Syntax is      halt [-d | -f | -h | -n | -i | -p | -w]     reboot [-d | -f | -i | -n | -w]     poweroff [-d | -f | -h | -n | -i | -w]

OPTIONS:     

- d Don't write wtmp record(into /var/log/wtmp file). The -n flag implies -d

- hput all harddrives in the system in standby mode before the system is halted or turnedoff

- n Don't sync before reboot or halt

- i shutdown all network interface.

- pWhile halting the system, also turnoff the system. This is default when halt is called as poweroff.

- w Don't actually reboot or halt but only write wtmp record (into /var/log/wtmp file)

EXAMPLE:     

1. To halt the system:

halt

This command is similar to poweroff, which shutdown the system.

Page 36: Linux & Unix Command

2. To Poweroff the system:

poweroff

Poweroff command used for turnoff the system.

3. To reboot the system:

reboot

Reboot command used for reboots/restarts the system.Explanation

head COMMAND:     head command is used to display the first ten lines of a file, and also specifies how many lines to display.

SYNTAX:  The Syntax is      head [options] filename

OPTIONS:     

-n To specify how many lines you want to display.

-n numberThe number option-argument must be a decimal integer whose sign affects the location in the file, measured in lines.

-c numberThe number option-argument must be a decimal integer whose sign affects the location in the file, measured in bytes.

EXAMPLE:     

1. head index.php This command prints the first 10 lines of 'index.php'.

2. head -5 index.php The head command displays the first 5 lines of 'index.php'.

3. head -c 5 index.php The above command displays the first 5 characters of 'index.php'.Explanation

host COMMAND:     host command is used to find the ip address of the given domain name and also prints the domain name for the given ip.

SYNTAX:  The Syntax is      host [-aCdlnrTwv] domain-name/ipaddress

OPTIONS:     

-a Prints all the DNS records for the given hostname.

-C Prints the SOA records and authorative name servers.

-d It is equivalent to -v.

-l Lists all hosts in a domain using AXFR.

Page 37: Linux & Unix Command

-tused to select the query type.Query Type: CNAME,NS,SOA,KEY etc,.

-W Specifies how long to wait for a reply.

-v Verbose output is generated by host.

-TUse TCP instead of UDP to query nameserver. This is implied in queries that require TCP, such as AXFR requests.

EXAMPLE:     

1. To find the ipaddress of a hostname 

host 123456789.co.in

123456789.co.in has address 69.65.102.222By typing the hostname along with the host command you can get its ipaddress. The ip address of 123456789.co.in is 69.65.102.222

2. To Print SOA record information:

host -C 123456789.co.in

Nameserver ns1.dnshorizon.com: 123456789.co.in SOA ns1.dnshorizon.com. saisan.gmail.com.

2007062001 86400 7200 3600000 86400Nameserver ns2.dnshorizon.com: 123456789.co.in SOA ns1.dnshorizon.com. saisan.gmail.com.

2007062001 86400 7200 3600000 86400The above cmd prints the host's nameserver and its SOA record.

Explanation

hostid COMMAND:     hostid command prints the numeric identifier or id of the current host in hexadecimal.

SYNTAX:  The Syntax is      hostid

OPTIONS:     

--help Print help message and exit

--version

Print version and exit

EXAMPLE:     

Page 38: Linux & Unix Command

1. To Print host id:2. hostid

3. a3b50706

This command prints the hostid in hexadecimal.Explanation

hostname COMMAND:     hostname specifies the name of the host.

SYNTAX:  The Syntax is      hostname [-a | -d | -f | -h | -i | -s]

OPTIONS:     

-a Displays the alias name of the host, if used.

-d Displays DNS domain name

-f Displays fully qualified domain name.

-h Displays help message.

-i Displays IP address of the host.

-s Trim domain name from display.

EXAMPLE:     

1. hostname command

hostnameThe above command will print as username.com

2. hostname -a

The above command will remove space and print as username

3. To display DNS domain name

hostname -dThe above command will print as .comExplanation

id COMMAND:     id command prints the effective(current) and real userid(UID)s and groupid(GID)s.

SYNTAX:  The Syntax is      id [options]

OPTIONS:     

-a Reports user name, use ID and all the groups to which the user belongs.

Page 39: Linux & Unix Command

-G Output all real and effective group IDs,using the format "%u\n".

-g Output only the effective group IDs,using the format "%u\n".

-u Output only the effective user Id,using the format "%u\n".

EXAMPLE:     

1. id -aOutput:uid=501(username) gid=501(username) groups=48(apache),501(username)Prints real and current group IDs.

2. id -GOutput:501 48Prints in the format of "%u\n"

3. # id Output:uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel) context=user_u:system_r:unconfined_tThe above example display the rootuser uid, gid, groups and context.Explanation

info COMMAND:     info command is used to display the readable online documentation for the specified command .

SYNTAX:  The Syntax is      info commandname

OPTIONS:     

-n Specify nodes in first visited info file.

-f Specify info file to visit.

EXAMPLE:     

1. info manDisplay the readable online documentation for the man command.Explanation

ifconfig COMMAND:      ifconfig command displays information about the network interfaces attached to the system and also used to configure the network interface.

SYNTAX:  The Syntax is      ifconfig [options]

OPTIONS:     

-adispalys information about both active and inactive Interface

[interface-name] dispalys information about interface

Page 40: Linux & Unix Command

[interface-name] up Activates the interface

[interface-name] down Inactivates the interface

[interface-name] [IP Address] up Assigns IP address to the interface and activates it

EXAMPLE:     

1. To get information of active network-interfaces:

ifconfigThe sample output of above command:

eth0Link encap:Ethernet HWaddr 00:14:85:9C:CC:55inet addr:192.168.0.12 Bcast:192.168.0.255 Mask:255.255.255.0inet6 addr: fe80::214:85ff:fe9c:cc55/64 Scope:LinkUP LOOPBACK RUNNING MTU:16436 Metric:1RX packets:7856 errors:0 dropped:0 overruns:0 frame:0TX packets:7856 errors:0 dropped:0 overruns:0 carrier:0RX bytes:492016 (480.4 KiB) TX bytes:398 (398.0 b)Interrupt:201 Memory:e1000000-0

loLink encap:Local Loopbackinet addr:127.0.0.1 Mask:255.0.0inet6 addr: ::1/128 Scope:HostUP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1RX packets:1455 errors:0 dropped:0 overruns:0 frame:0TX packets:5 errors:0 dropped:0 overruns:0 carrier:0RX bytes:1917382 (1.8 MiB) TX bytes:1917382 (1.8 MiB)

In above output:Link encap:Ethernet -Specifies the type InterfaceHWaddr 00:14:85:9C:CC:55 -Specifies the Hardware or MAC addressinet addr:192.168.0.12 -Specifies the IP address assigend to network-interface

2. To Assign IP address to Network Interface[Ethernet Card]:

ifconfig eth0 192.168.0.12 upThe above command will Assign IP address 192.168.0.12 to Ethernet card with name eth0.

3. To inactivate the Network Interface[Ethernet Card]:

ifconfig eth0 downThe above command inactivates the ethernet card.Explanation

jobs COMMAND:     jobs command is used to list the jobs that you are running in the background and in the foreground. If the prompt is returned with no information no jobs are present.

SYNTAX:  The Syntax is      jobs [options]

OPTIONS:

Page 41: Linux & Unix Command

     

-l Report the process group ID and working directory of the jobs.

-n Display only jobs that have stopped or exited since last notified.

-p Displays only the process IDs for the process group leaders of the selected jobs.

EXAMPLE:     

1. jobs -lLists the jobs that you are running in the foreground (or) background.

2. jobs -pDisplay only the process Id for the listed jobs.

kill COMMAND:     kill command is used to kill the background process.

SYNTAX:  The Syntax is      kill [-s] [-l] %pid

OPTIONS:     

-s Specify the signal to send. The signal may be given as a signal name or number.

-l Write all values of signal supported by the implementation, if no operand is given.

-pid Process id or job id.

-9 Force to kill a process.

EXAMPLE:     

Step by Step process:

Open a process music player.xmms

press ctrl+z to stop the process.

To know group id or job id of the background task.jobs -l

It will list the background jobs with its job id as, xmms 3956

kmail 3467

To kill a job or process.kill 3956

kill command kills or terminates the background process xmms.

Explanation

last COMMAND:     last command is used to display the last logged in users list. Last logged in users informations are read from the file /var/log/wtmp.

SYNTAX:

Page 42: Linux & Unix Command

  The Syntax is      last [options]

OPTIONS:     

-n Specify how many lines to show.

-R Suppresses the display of the hostname field.

-x Display the system shutdown entries and run level changes.

-a Display the hostname in the last column. Useful in combination with the next flag.

EXAMPLE:     

1. last

Displays the last logged in users list.

2. last -x

Displays the logged in users list with shutdown entries and run level changes.Explanation

lastlog COMMAND:     lastlog command is used to print the last login times for system accounts. Login information is read from the file /var/log/lastlog.

SYNTAX:  The Syntax is      lastlog [options]

OPTIONS:     

-t n Print only logins more recent than 'n' days ago..

-u username Print only login information for username.

EXAMPLE:     

1. lastlog -t 5Displays the login information, 5 days ago.

2. last -u username Displays the login information for the specified user.Explanation

less COMMAND:     less command is used to display text in the terminal screen. It just prints the text in the given file, you cannot edit or manipulate the text here. To display the file from the specified line, enter the line number followed by colon(:). It allows Forward and backward movement in the file.

SYNTAX:  The Syntax is      less [options] filename

OPTIONS:     

Page 43: Linux & Unix Command

-c Clear screen before displaying.

+n Starts up the file from the given number.

:p Examine the pervious file in the command line list.

:d Remove the current file from the list of files.

EXAMPLE:     

1. less +3 index.phpStart printing from 3rd line of the file.Explanation

link COMMAND:     link command is used to create a link to a file. It is also called as hard link. Inode will be same for source and destination.

SYNTAX:  The Syntax is      link existingfilename newfilename (or) link source destination

OPTIONS:     

--help Print help message and exit

--version

Print version and exit

EXAMPLE:     

1. link test.php test1.phpCreate a link to 'test1.php' file. Here inode for 'test.php' and 'test1.php' will be same.

ln COMMAND:     ln command is used to create link to a file (or) directory. It helps to provide soft link for desired files. Inode will be different for source and destination.

SYNTAX:  The Syntax is      ln [options] existingfile(or directory)name newfile(or directory)name

OPTIONS:     

-fLink files without questioning the user, even if the mode of target forbids writing. This is the default if the standard input is not a terminal.

-n Does not overwrite existing files.

-s Used to create soft links.

EXAMPLE:     

1. ln -s file1.txt file2.txt

Creates a symbolic link to 'file1.txt' with the name of 'file2.txt'. Here inode for 'file1.txt' and 'file2.txt' will be different.

Page 44: Linux & Unix Command

2. ln -s nimi nimi1

Creates a symbolic link to 'nimi' with the name of 'nimi1'.

Explanation

ls COMMAND:     ls command lists the files and directories under current working directory.

SYNTAX:  The Syntax is      ls [OPTIONS]... [FILE]

OPTIONS:     

-lLists all the files, directories and their mode, Number of links, owner of the file, file size, Modified date and time and filename.

-t Lists in order of last modification time.

-a Lists all entries including hidden files.

-d Lists directory files instead of contents.

-p Puts slash at the end of each directories.

-u List in order of last access time.

-i Display inode information.

-ltr List files order by date.

-lSr List files order by file size.

EXAMPLE:     

1. Display root directory contents:

ls /

lists the contents of root directory.

2. Display hidden files and directories: 

ls -a

lists all entries including hidden files and directories.

3. Display inode information: 

ls -i7373073 book.gif 7373074 clock.gif 7373082 globe.gif 7373078 pencil.gif7373080 child.gif 7373081 email.gif

Page 45: Linux & Unix Command

7373076 indigo.gif

The above command displays filename with inode value.Explanation

lsattr COMMAND:     lsattr command is used to list the attributes of the specified file or directory.

SYNTAX:  The Syntax is      lsattr [options]

OPTIONS:     

-R Recursively list attributes of directories and their contents.

-a List all files in directories, including files that start with `.'.

-d List directories like other files, rather than listing their contents.

EXAMPLE:     

1. List attributes:

lsattr Lists the attributes of the current directory.

2. Set the attribute:

chattr +i test.txt Set the attribute for 'test.txt' file.

3. lsattr test.txt Lists the attributes of the 'test.txt' file.----i-------- ./test.txtExplanation

mail COMMAND:     mail command is used to send and receive mails locally and globally.

SYNTAX:  The Syntax is      mail

OPTIONS:     

-s Specify subject on command line.

-c Send carbon copies to list of users.

-bSend blind carbon copies to list. List should be a comma-separated list of names.

-fRead in the contents of your mbox for processing; when you quit, mail writes undeleted messages back to this file.

-iIgnore tty interrupt signals. This is particularly useful when using mail on noisy phone lines.

Page 46: Linux & Unix Command

EXAMPLE:     

1. Receive mails

mailThe above command display the messages. Press Enter to view the next message after '&' symbol.

2. Sent mails

mail [email protected] (or) mail [email protected] a new mail and sent to [email protected] terminate the message, type a period(.) and press Enter (or) press ctrl+d and press Enter.Explanation

man COMMAND:     man command which is short for manual, provides in depth information about the requested command (or) allows users to search for commands related to a particular keyword.

SYNTAX:  The Syntax is      man commandname [options]

OPTIONS:     

-a Print a one-line help message and exit.

-k Searches for keywords in all of the manuals available..

EXAMPLE:     

1. man mkdirDisplay the information about mkdir command.Explanation

mkdir COMMAND:     mkdir command is used to create one or more directories.

SYNTAX:  The Syntax is      mkdir [options] directories

OPTIONS:     

-m Set the access mode for the new directories.

-p Create intervening parent directories if they don't exist.

-v Print help message for each directory created.

EXAMPLE:     

Page 47: Linux & Unix Command

1. Create directory: 

mkdir testThe above command is used to create the directory 'test'.

2. Create directory and set permissions:

mkdir -m 666 testThe above command is used to create the directory 'test' and set the read and write permission.Explanation

more COMMAND:     more command is used to display text in the terminal screen. It allows only backward movement.

SYNTAX:  The Syntax is      more [options] filename

OPTIONS:     

-c Clear screen before displaying.

-e Exit immediately after writing the last line of the last file in the argument list.

-n Specify how many lines are printed in the screen for a given file.

+n Starts up the file from the given number.

EXAMPLE:     

1. more -c index.phpClears the screen before printing the file .

2. more -3 index.phpPrints first three lines of the given file. Press Enter to display the file line by line.Explanation

mv COMMAND:     mv command which is short for move. It is used to move/rename file from one directory to another. mv command is different from cp command as it completely removes the file from the source and moves to the directory specified, where cp command just copies the content from one file to another.

SYNTAX:  The Syntax is      mv [-f] [-i] oldname newname

OPTIONS:     

-fThis will not prompt before overwriting (equivalent to --reply=yes). mv -f will move the file(s) without prompting even if it is writing over an existing target.

-i Prompts before overwriting another file.

EXAMPLE:     

Page 48: Linux & Unix Command

1. To Rename / Move a file:

mv file1.txt file2.txt This command renames file1.txt as file2.txt

2. To move a directory

mv hscripts  tmpIn the above line mv command moves all the files, directories and sub-directories from hscripts folder/directory to tmp directory if the tmp directory already exists. If there is no tmp directory it rename's the hscripts directory as tmp directory.

3. To Move multiple files/More files into another directory 

mv file1.txt tmp/file2.txt newdirThis command moves the files file1.txt from the current directory and file2.txt from the tmp folder/directory to newdir.Explanation

netstat COMMAND:      nestat command displays statistics information and current state of network connections, protocol, ports/ sockets and devices.

SYNTAX:  The Syntax is      netstat [options]

OPTIONS:     

-s dispalys statics information about protocols.

-i dispalys statistics information about the network interface.

-r diplays routing table.

-c displays statistics information and updates every second.

-l displays information about all sockets that are in listening state.

-adisplays information about all sockets that are in listening and non-listening state.

-p displays information about sockets with ProcessName and PID.

EXAMPLE:     

1. To get statistics of network connections:

netstatThe sample output of above command:

Active Internet connections (w/o servers)

Proto Recv-Q Send-Q Local Address Foreign Address Statetcp 0 0 vhost:32803 LocalHost:smtp TIME_WAITtcp 0 0 vhost:32803 google.com:http ESTABLISHED

Page 49: Linux & Unix Command

Where,Proto -Specifies the Protocol used for connection.Recv-Q -Specifies the Number of Bytes which are not recevied.Send-Q -Specifies the Number of Bytes not send to destination.Local Address -Specifies the local or source address and port.Foreign Address -Specifies the destination address and port.State -Specifies the current state of conection to the socket.

o ESTABLISHED - Connection is Established.o TIME_WAIT - Waiting to receive packets.o LISTEN - Listening to establish connection.

2. To Get Statistics of Protocols:

netstat -sThe Sample output of above command:

IP:5193 incoming packets delivered4813 requests sent out

Tcp:4033 segments received4813 segments send out

Icmp:41 ICMP messages received178 ICMP messages sent

3. To Get statistics of Network Interface:

netstat -iThe sample output of above command:

Kernel Interface table

Iface MTU Met RX-OK RX-ERR TX-OK TX-ERR Flgeth0 1500 0 1308 0 1345 0 BMRU

This is the statistics information of Ethernet Card[eth0].Explanation

passwd COMMAND:     passwd command is used to change your password.

SYNTAX:  The Syntax is      passwd [options] 

OPTIONS:     

-a Show password attributes for all entries.

-l Locks password entry for name.

-d Deletes password for name. The login name will not be prompted for password.

-fForce the user to change password at the next login by expiring the password for name.

EXAMPLE:

Page 50: Linux & Unix Command

     1. passwd

Entering just passwd would allow you to change the password. After entering passwd you will receive the following three prompts: Current Password: New Password: Confirm New Password: Each of these prompts must be entered correctly for the password to be successfully changed.Explanation

paste COMMAND:     paste command is used to paste the content from one file to another file. It is also used to set column format for each line.

SYNTAX:  The Syntax is      paste [options]

OPTIONS:     

-s Paste one file at a time instead of in parallel.

-d Reuse characters from LIST instead of TABs .

EXAMPLE:     

1. paste test.txt>test1.txt Paste the content from 'test.txt' file to 'test1.txt' file.

2. ls | paste - - - - List all files and directories in four columns for each line.Explanation

pidof COMMAND:     pidof linux command is used to find the process ID of a running program.

SYNTAX:  The Syntax is      pidof [options..] program

OPTIONS:     

-s Single shot - this instructs the program to only return one pid.

-xScripts too - this causes the program to also return process id's of shells running the named scripts.

-oTells pidof to omit processes with that process id. The special pid %PPID can be used to name the parent process of the pidof program, in other words the calling shell or shell script.

EXAMPLE:     

1. To find a process id of a particular console:

pidof -s consoleThis command prints the process id of the console.

Page 51: Linux & Unix Command

3189Explanation

ping COMMAND:     System administration command. Confirm that a remote host is online and responding. Ping is used for verifying connectivity between two hosts on a network. It sends Internet Control Message Protocol (ICMP) echo request packets to a remote IP address and watches for ICMP responses.

SYNTAX:  The Syntax is      ping [options] host

OPTIONS:     

-a Make ping audible. Beep each time response is received.

-b Ping a broadcast address.

-c countStop after sending count ECHO_REQUEST packets. With deadline option, ping waits for count ECHO_REPLY packets, until the timeout expires.

-nShow network addresses as numbers. ping normally displays addresses as host names.

-qQuiet output—nothing is displayed except the summary lines at startup time and when finished.

-iSpecify the interval between successive transmissions. The default is one second.

-t Set the IP Time to Live to n seconds.

-w Exit ping after n seconds.

EXAMPLE:     

1. ping google.com -c 3Display ECHO_REQUEST 3 times only because we set count for three.

2. ping -n google.com Here the network addresses displays as numbers,normally it displays as hostnames.Explanation

printf COMMAND:     printf command is used to write formatted output.

SYNTAX:  The Syntax is      printf format [argument]....

OPTIONS:     The format characters and their meanings are:

\b Backspace.

\n Newline.

\t Horizontal tab

\v Vertical tab.

EXAMPLE:

Page 52: Linux & Unix Command

     1. printf "hello\n"

Use '\n' returns 'hello' to the new line.2. printf "hel\blo"

Output:heloHere '\b' is used for backspace.Explanation

ps COMMAND:     ps command is used to report the process status. ps is the short name for Process Status.

SYNTAX:  The Syntax is      ps [options]

OPTIONS:     

-aList information about all processes most frequently requested: all those except process group leaders and processes not associated with a terminal..

-A or e List information for all processes.

-d List information about all processes except session leaders.

-e List information about every process now running.

-f Generates a full listing.

-j Print session ID and process group ID.

-l Generate a long listing.

EXAMPLE:     

1. psOutput: PID TTY TIME CMD 2540 pts/1 00:00:00 bash 2621 pts/1 00:00:00 psIn the above example, typing ps alone would list the current running processes.

2. ps -f Output:UID PID PPID C STIME TTY TIME CMDnirmala 2540 2536 0 15:31 pts/1 00:00:00 bashnirmala 2639 2540 0 15:51 pts/1 00:00:00 ps -fDisplays full information about currently running processes.Explanation

pwd COMMAND:     pwd - Print Working Directory. pwd command prints the full filename of the current working directory.

SYNTAX:  The Syntax is      pwd [options]

OPTIONS:     

-P The pathname printed will not contain symbolic links.

-L The pathname printed may contain symbolic links.

Page 53: Linux & Unix Command

EXAMPLE:     

1. Displays the current working directory.

pwdIf you are working in home directory then, pwd command displays the current working directory as/home.Explanation

restore COMMAND:     restore - command restores the data from the dump-file or backup-file created using dump command.

SYNTAX:  The Syntax is      restore [options]

OPTIONS:     

-f Used to specify the backup or dump file

-C Used to compare dump-file with original file

-i Restore in Interactive mode

-v Displays Verbose Information

-e Exclude inode while making backup

    Commands used in interactive mode:

ls List the files and directories in backup file

add Add files in dump-file to current working directory

cd Changes the directory

pwd Displays the current working directory

extract Extract the files from the dump

quit Quit from the interactive mode

EXAMPLE:     

1. To restore file and directories from backup-file :

restore -if databackWhere,i -To make restore with interactive modef -To restore from the backup-file specifeddataback -Is a name of backup-file or dump-file

This command gets you to interactive mode as follows:restore >Now the following commands are entered to restore:restore > ls -Lists files and directories in dump file

Page 54: Linux & Unix Command

restore > add -add files to the current directoryrestore > ls -Lists the file added from the backup file to current directoryrestore > extract -Extracts the file from the backup file to current directoryrestore > quit -Quits from the interactive mode

2. To compare and display any dump-file with the original file:

restore -Cf databackThis command will compare,

-1 -Is the dump-level [1 specifies incremental backup]databackup -Is a dump-file [or backup-file]/home/user1/data -Is a directory for which a backup is created

Explanation

rm COMMAND:     rm linux command is used to remove/delete the file from the directory.

SYNTAX:  The Syntax is      rm [options..] [file | directory]

OPTIONS:     

-f Remove all files in a directory without prompting the user.

-iInteractive. With this option, rm prompts for confirmation before removing any files.

-r (or) -RRecursively remove directories and subdirectories in the argument list. The directory will be emptied of files and removed. The user is normally prompted for removal of any write-protected files which the directory contains.

EXAMPLE:     

1. To Remove / Delete a file:

rm file1.txtHere rm command will remove/delete the file file1.txt.

2. To delete a directory tree:

rm -ir tmpThis rm command recursively removes the contents of all subdirectories of the tmp directory, prompting you regarding the removal of each file, and then removes the tmp directory itself.

3. To remove more files at once

rm file1.txt file2.txtrm command removes file1.txt and file2.txt files at the same time.Explanation

rmdir COMMAND:     rmdir command is used to delete/remove a directory and its subdirectories.

SYNTAX:

Page 55: Linux & Unix Command

  The Syntax is      rmdir [options..] Directory

OPTIONS:     

-pAllow users to remove the directory dirname and its parent directories which become empty.

EXAMPLE:     

1. To delete/remove a directory 

rmdir tmprmdir command will remove/delete the directory tmp if the directory is empty.

2. To delete a directory tree:

rm -ir tmpThis command recursively removes the contents of all subdirectories of the tmp directory, prompting you regarding the removal of each file, and then removes the tmp directory itself.Explanation

route COMMAND:     route command displays routing table resides in kernel and also used to modify the routing table.The tables which specifies how packets are routed to a host is called routing table.

SYNTAX:  The Syntax is      route [options]

OPTIONS:     

-n dispalys routing table in numerical[IP Address] format

-e dispalys routing table in Hostname format

add Adds a new route to the routing table

del Deletes a route from the routing table

    Options used with add and del :

-net Indicate the target is network

-host Indicate the target is host

gw Specifies the gateway of target host/network

netmaskUsed to specifiy the subnet-mask of destination network/host

devSpecify the device or interface where the packets will be sent

reject rejects the packets sent to particular route/host

EXAMPLE:     

Page 56: Linux & Unix Command

1. To dispaly the routing table:

route -nThe above command will print: 

Destination Gateway Genmask Flags Metric Ref Use Iface192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0

0.0.0.0 192.168.0.1 0.0.0.0 UG 0 0 0 eth0

In above table:Destination -Indicates the IP address of desination host/networkGateway -Indicates gateway from which desination host/network could be reachedGenmask -Indicates the subnetmask destinationFlags -Indicates the current status of route

o U - Route is upo H - Target is a hosto G - Use gateway

Iface -Indicates the interface2. To add static route to a network in the routing table:

route add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.1 dev eth0In above command:add -Indicates that the route is added to routing table.-net -Indicates that desination is a network.192.168.0.1 -Indicates IP address of destination network.netmask -Indicates the subnetmask of destination network.gw 192.168.1.1 -Indicates the gateway of destination network.dev eth0 -Indicates that the packets are routed via the interface eth0.

3. To delete a route from the routing table:

route del -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.1 dev eth0The above command will delete the route to 192.168.1.0 from the routing table.Explanation

sort COMMAND:     sort command is used to sort the lines in a text file.

SYNTAX:  The Syntax is      sort [options] filename

OPTIONS:     

-r Sorts in reverse order.

-u If line is duplicated display only once.

-o filename Sends sorted output to a file.

EXAMPLE:

Page 57: Linux & Unix Command

     1. sort test.txt

Sorts the 'test.txt'file and prints result in the screen.2. sort -r test.txt

Sorts the 'test.txt' file in reverse order and prints result in the screen.Explanation

sed COMMAND:     sed is a stream editor. sed command helps to edit or delete all occurrences of one string to another within a file. It takes a file as input and prints the result on screen or redirects the output to a specified file.

SYNTAX:  The Syntax is      sed [options] '{command}' [filename]

OPTIONS:      Command and its function

-n do not output the trailing newline

-e enable interpretation of the backslash-escaped characters listed below

-E disable interpretation of those sequences in STRINGs

    Without -E, the following sequences are recognized and interpolated:

\NNN the character whose ASCII code is NNN (octal)

\a alert (BEL)

\b backspace

\c suppress trailing newline

\f form feed

\n new line

\r carriage return

\t horizontal tab

\v vertical tab

EXAMPLE:     Lets assume that we have a file file1.txt and it has the following data.

hscripts has many valuable free scriptsIt is the parent site of www.forums.hscripts.comhscripts include free tutorials and free gif imagesfree DNS lookup toolPurchase scripts from usA webmaster/web master resource website1. sed G file1.txt>file2.txt2. In the above example, using the sed command with G would double space the file file1.txt

and output the results to the file2.txt.3. sed = file1.txt | sed 'N;s/\n/\. /'

In the above example, sed command is used to output each of the lines in file1.txt with the line number followed by a period and a space before each line.

4. sed 's/scripts/javascript/g' file1.txt Opens the file file1.txt and searches for the word 'scripts' and replaces every occurrence with the word 'javascript'.

5. sed -n '$=' file1.txtThe above command count the number of lines in the file1.txt and output the results.Explanation

Page 58: Linux & Unix Command

Shutdown COMMAND:     Shutdown - Turn off the computer immediately or at a specified time.

Shutdown / Turn off brings the system down in a secure way. All logged-in users are notified that the system is going down, and login(1) is blocked. It is possible to shut the system down immediately or after a specified delay. All processes are first notified that the system is going down by the signal SIGTERM.

This gives programs like vi(1) the time to save the file being edited, mail and news processing programs a chance to exit cleanly, etc. Shutdown does its job by signalling the init process, asking it to change the runlevel. Runlevel 0 is used to halt the system, runlevel 6 is used to reboot the system, and runlevel 1 is used to put to system into a state where administrative tasks can be performed; this is the default if neither the -h or -r flag is given to shutdown.

To see which actions are taken on halt or reboot see the appropriate entries for these runlevels in the file /etc/inittab.

SYNTAX:  The Syntax is       /sbin/shutdown [-t sec] [-arkhncfFHP] time [warning-message]

OPTIONS:     

-a Use /etc/shutdown.allow.

-t secTell init(8) to wait sec seconds between sending processes the warning and the kill signal, before changing to another runlevel.

-k Don’t really shutdown; only send the warning messages to everybody.

-r Reboot after shutdown.

-h Halt or poweroff after shutdown.

-H Halt action is to halt or drop into boot monitor on systems that support it.

-P Halt action is to turn off the power.

-f Skip fsck on reboot.

-F Force fsck on reboot.

-c Cancel an already running shutdown.

EXAMPLE:     

shutdown 10:00Shutdown the computer at 10-oclock

Explanation

tail COMMAND:     tail command is used to display the last or bottom part of the file. By default it displays last 10 lines of a file.

SYNTAX:  The Syntax is      tail [options] filename

OPTIONS:     

Page 59: Linux & Unix Command

-l To specify the units of lines.

-b To specify the units of blocks.

-n To specify how many lines you want to display.

-c numberThe number option-argument must be a decimal integer whose sign affects the location in the file, measured in bytes.

-n numberThe number option-argument must be a decimal integer whose sign affects the location in the file, measured in lines.

EXAMPLE:     

1. tail index.php It displays the last 10 lines of 'index.php'.

2. tail -2 index.php It displays the last 2 lines of 'index.php'.

3. tail -n 5 index.php It displays the last 5 lines of 'index.php'.

4. tail -c 5 index.php It displays the last 5 characters of 'index.php'.Explanation

tar COMMAND:     tar command is used to create archive and extract the archive files.

SYNTAX:  The Syntax is      tar [options] [archive-file] [File or directory to be archived]

OPTIONS:     

-c Creates Archive

-x Extract the archive

-f creates archive with give filename

-t displays or lists files in archived file

-u archives and adds to an existing archive file

-v Displays Verbose Information

-A Concatenates the archive files

EXAMPLE:     

1. To archive a directory or file :

tar -cvf backup.tar /etcThis command creates a tarfile called backup.tar which is the archive of /etc directory.

Where,backup.tar - Is a tar file created/etc - Is a directory archived

2. To archive a directory or file and store it in a storage device:

tar -cvf /dev/fd0 /home/user1/HGB

Page 60: Linux & Unix Command

This command will archive /etc directory and store it in floppy-disk.Where,/dev/fd0 - Is a floppy-disk name where the archive is stored/home/user1/HGB - Is a directory archived

3. To Extract the archive:

tar -xvf backup.tarThis command will extract the backup.tar file

4. To List The File In An Archive:

tar -tvf backup.tarThe above command will display the files and directories that archived in backup.tar.Explanation

useradd COMMAND:     useradd - Adds new user to the linux system, with specified user-name. When a new user is added then a corresponding entry is made in files /etc/passwd, /etc/group and /etc/shadow

SYNTAX:  The Syntax is      useradd [options] [username]

OPTIONS:     

-d Specifies the users home directory

-s Specifies the users shell

-g Specifies the users primary group

-G Specifies the users secondary groups

-M Specifies not to create home directory for the user

-e Specifies the expire date of the user

-uid Specifies the user-id of the user

EXAMPLE:     

1. To add new user:

useradd hioxThis command will add a new user with name hiox.

2. To add user but not allow to login in the system:

useradd -s /bin/nologin hioxThis command will add user hiox but not allow to login.

In above command:hiox -Is the user-name/bin/nologin -Is Shell assigned to the user

3. To set expire date of the user:

useradd -e 2008-06-30 hioxThis command will add user hiox and set the expire date to 2008-06-30.

Page 61: Linux & Unix Command

In above command:hiox -Is the user-name2008-06-30 -Is date on which the user-account will be expired

4. To create user without creating home directory:

useradd -M hioxThe above command will create user hiox but home directory will not be created.Explanation

who COMMAND:      who command can list the names of users currently logged in, their terminal, the time they have been logged in, and the name of the host from which they have logged in.

SYNTAX:  The Syntax is      who [options] [file]

OPTIONS:     

am iPrint the username of the invoking user, The 'am' and 'i' must be space separated.

-b Prints time of last system boot.

-d print dead processes.

-H Print column headings above the output.

-iInclude idle time as HOURS:MINUTES. An idle time of . indicates activity within the last minute.

-m Same as who am i.

-q Prints only the usernames and the user count/total no of users logged in.

-T,-w Include user's message status in the output.

EXAMPLE:     

1. who -uHOutput:NAME LINE TIME IDLE PID COMMENThiox ttyp3 Jul 10 11:08 . 4578This sample output was produced at 11 a.m. The "." indiacates activity within the last minute.

2. who am i

who am i command prints the user name.Explanation

whois COMMAND:     whois command lists the information about the domain owner of the given domain.

SYNTAX:  The Syntax is      whois [option] query

OPTIONS:     

-h Host which holds the identification information in its database.

Page 62: Linux & Unix Command

-p connect to the specified port.

EXAMPLE:     

1. whois hscripts.comOutput:The above command will produce the following output.

[Querying whois.internic.net][Redirected to whois.PublicDomainRegistry.com][Querying whois.PublicDomainRegistry.com][whois.PublicDomainRegistry.com]Registration Service Provided By: HIOX INDIAContact: +91.4226547769

Domain Name: HSCRIPTS.COM

Registrant: HIOX INDIA Rajesh Kumar ([email protected]) 32, North Street, Krishnapuram, Singanallur Coimbatore tamil nadu,641005 IN Tel. +91.04225547769

Creation Date: 06-Oct-2004Expiration Date: 06-Oct-2008

Domain servers in listed order: ns1.hscripts.com ns2.hscripts.com

Administrative Contact: HIOX INDIA Rajesh Kumar ([email protected]) 32, North Street, Krishnapuram, Singanallur Coimbatore tamil nadu,641005 IN Tel. +91.04225547769

Technical Contact: HIOX INDIA Rajesh Kumar ([email protected]) 32, North Street, Krishnapuram, Singanallur Coimbatore tamil nadu,641005 IN Tel. +91.04225547769

Billing Contact: HIOX INDIA Rajesh Kumar ([email protected]) 32, North Street, Krishnapuram, Singanallur

Page 63: Linux & Unix Command

Coimbatore tamil nadu,641005 IN Tel. +91.04225547769

Status:ACTIVE

The data in this whois database is provided toyou for information purposes only, that is,to assist you in obtaining information about orrelated to a domain name registration record.We make this information available "as is", and do not guarantee its accuracy. By submitting awhois query, you agree that you will use this dataonly for lawful purposes and that, under nocircumstances will you use this data to:(1) enable high volume, automated, electronic processes that stress or load this whois database system providing you this information; or(2) allow, enable, or otherwise support the transmission of mass unsolicited, commercial advertising or solicitations via fascimile,electronic mail, or by telephone. The compilation,repackaging, dissemination or other use of this datais expressly prohibited without prior written consentfrom us. The registrar of record is PublicDomainRegistry.We reserve the right to modify these terms at any time.By submitting this query, you agree to abideby these terms.

This sample output was produced at 11 a.m. The "." indicates activity within the last minute.Explanation

yes COMMAND:     yes command repeatedly prints the given string separated by a space and followed by a newline until it is killed. If no string is given, it just prints 'y' repeatedly until it is killed. It is normally used in scripts, its output is piped to a command or program that prompts you to do this or that (do you want to delete this file press 'y' or 'n')

SYNTAX:  The Syntax is      yes [string..]     yes [options..]

OPTIONS:     

--help Print help message and exit

--version

Print version and exit

EXAMPLE:     

1. Print the given string repeatedly:

Page 64: Linux & Unix Command

yes "hscripts"The above command will print hscripts repeatedly until it is killed(CTRL+C).

2. To delete a file without pressing any key when it prompts:

yes | rm -i *.txtIn the above example, the yes command is piped with rm command. Normally rm -i will prompt you to remove the file, to remove the file you have to type either y(yes) or n(no). When it is piped with yes by default, the yes will print y and all the txt files will be removed automatically, so that you dont need to type y for every txt files.yes n | rm -i *.txtThe above example says not to remove a file when rm -i prompts to remove the file.