Gaurav at 04:54, 16 July 2015

2015-07-16T04:54:23Z

Ashwini: Created page with ''''Title of script''':''' Command line arguments and Quoting''' '''Author: '''FOSSEE and spoken-tutorial team '''Keywords: '''Video tutorial,''' '''Command Line Arguments, Sing…'

2013-07-26T09:21:44Z

Created page with ''''Title of script''':''' Command line arguments and Quoting''' '''Author: '''FOSSEE and spoken-tutorial team '''Keywords: '''Video tutorial,''' '''Command Line Arguments, Sing…'

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'''Title of script''':''' Command line arguments and Quoting'''

'''Author: '''FOSSEE and spoken-tutorial team

'''Keywords: '''Video tutorial,''' '''Command Line Arguments, Single quote, Double quote, Backslash

{| style="border-spacing:0;"
! <center>Visual Cue</center>
! <center>Narration</center>

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display Slide
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Welcome to the spoken tutorial on''' Command line arguments and Quoting in BASH'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display Slide
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| In this tutorial, we will learn about

* '''Command line Arguments'''
* '''Quoting'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display Slide

'''Prerequisites'''

'''spoken-tutorial.org '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| To follow this tutorial, you should be familiar with the '''Linux Operating System.'''

If not, for relevant tutorials please visit''' spoken hyphen tutorial dot org.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display Slide

'''System Requirements'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| For this tutorial I am using

* '''Ubuntu Linux 12.04''' OS and
* '''GNU Bash''' version '''4.1.10'''

'''GNU Bash '''version '''4''' or above is recommended to practise this tutorial.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display slide :

'''Command Line arguments'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| * '''Shell script''' accepts '''arguments''' from the '''command line'''.
* The '''arguments''' are passed to the '''program''' being called.
* Any number of '''arguments''' can be passed to a '''program'''.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Press '''Ctrl+Alt+T'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let us open the '''terminal''' by pressing '''Ctrl+Alt+T''' keys.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| On '''terminal>> '''Type '''gedit arg.sh&>> '''press''' Enter'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| I have already written the code in the file named '''arg.sh'''

On the '''terminal, l'''et me open this file by typing,

'''gedit''' '''space arg.sh ampersand'''

Here '''ampersand '''is used to free up the '''prompt'''.

Press''' Enter.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"|
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let me explain the code now.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''<nowiki>#!/bin/bash </nowiki>'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This is a '''shenbang '''or a '''bang''' line.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| <nowiki>[highlight]</nowiki>

'''echo "zeroth arg: $0" '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This line will print the '''Zero<sup>th'''</sup> '''argument'''.

Here, '''$0 (Dollar zero) '''will print the name of the shell script.

This in turn means that, the '''zero<sup>th</sup> argument''' is the name of the '''program''' itself.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| <nowiki>[highlight]</nowiki>

'''echo "first arg: $1" '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''$1 (Dollar one) '''represents the first '''argument''' passed to the '''program''' from the''' command line'''.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| <nowiki>[highlight]</nowiki>

'''echo "second arg: $2"'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Similarly,

'''$2''' '''(Dollar two) '''represents the second '''argument''' passed to the '''program'''.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| <nowiki>[highlight] </nowiki>'''echo "third arg: $3" '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''$3 (Dollar three) '''represents the '''third argument'''.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| <nowiki>[highlight] </nowiki>'''echo "twelveth arg: ${12}" '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| And '''$12 (Dollar twelve) '''represents the''' twelveth '''argument.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| <nowiki>[highlight again!!]</nowiki>

'''echo "twelveth arg: ${12}"'''

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| To write an '''argument''' greater than 9, we need to use '''curly brackets'''.

Else '''bash''' will only take the '''argument''' of the integer in the '''ten's place'''.

And you will not get expected output.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''echo "total args: $#" '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| To continue with our code -

'''$# (Dollar hash)''' gives the total number of '''arguments''' that have been passed to a program'''.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''echo "Args(dollar *): $*"'''

'''for arg in “$*”'''

'''do'''

'''echo “$arg”'''

'''done'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''$* (Dollar asterix)''' will print all the '''arguments''' on a '''''single line'''. ''

We will test this with the help of a simple''' for '''loop.

We will analyse this '''for '''loop at the time of execution.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''echo "Args(dollar @): $@" '''

'''for arg in “$@”'''

'''do'''

'''echo “$arg”'''

'''done'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''$@ (Dollar at)''' will also print all the '''arguments'''. However, this time each '''argument''' will be on a '''''seperate line'''.''

This is another '''for''' loop, which will print each '''argument''' in a seperate line.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''exit 0'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''exit''' '''0 '''will exit the program.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"|
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Now, save the file.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Switch to '''terminal'''

Type:

'''chmod +x arg.sh'''

Press''' Enter'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| And make it executable by typing,

'''chmod''' '''space plus x space arg.sh'''

and press '''Enter.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"|
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''Command line arguments '''are given during execution.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Highlight:'''

Type:

'''./arg.sh sunday monday tuesday'''

Press '''Enter'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Now let us execute our '''Shell script''' by typing

'''dot slash arg.sh space sunday space monday space tuesday'''

Here '''sunday, monday '''and '''tuesday '''are the '''arguments''' we are passing.

Now press '''Enter.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"|
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let me explain the output.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Output:'''

'''zeroth arg: ./arg.sh '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The '''zeroth''' '''argument''' always displays the '''command '''used to execute the program.

So, you will see '''./arg.sh '''here.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Output:

'''first arg: sunday'''

'''second arg: monday '''

'''third arg: tuesday'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''sunday''' is assigned to the '''first argument'''.

'''monday '''is assigned to the '''second argument.'''

and '''tuesday '''is assigned to the '''third argument.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Output:

'''twelveth arg: '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''Twelveth argument''' is empty.

This is because we have passed only '''three arguments''' to the program.

Recall, this was the '''argument''' with '''curly brackets'''.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Output:'''

'''total args: 3 '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| We can see that total number of '''arguments''' i.e. '''3,''' is assigned to '''$# (Dollar hash)'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Args(dollar *): sunday monday tuesday'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| As we already said earlier, '''$* '''(D'''ollar asterix) '''will print all the '''arguments''' as on a single line.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''sunday monday tuesday'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This is the output of the first '''for '''loop.

We see that all '''arguments''' are printed on a single line.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Args(dollar @): sunday monday tuesday '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| These are the '''arguments''' printed by '''$@ (Dollar at)'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''sunday'''

'''monday'''

'''tuesday'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| And this is the output of the second '''for''' loop.

'''$@ (Dollar at)''' prints each '''argument''' on a seperate line.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"|
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| <nowiki><<PAUSE>></nowiki>

Let's move on.

Next, lets see '''Quoting '''is '''BASH.'''

Switch to the slides.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display slide

'''Quoting'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| There are three types of quotes in '''BASH'''

# '''Double quote'''
# '''Single quote'''
# '''Backslash'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display Slide

'''Double Quote'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| * '''Double quote '''substitutes the value of '''variables''' and '''commands'''
* Example: '''echo “Username is $USER”'''
* It displays your '''username '''on the system.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Switch to '''terminal>>'''Type '''echo “Username is $USER”>> press Enter'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let's switch to '''Terminal.'''

Type '''echo space opening double quote Username space is space dollar sign ''in capitals'' ''USER'' closing double quote '''

and Press '''Enter'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Output:'''

'''Highlight'''

'''“Username is lavitha” '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This will display your '''username '''

'''<nowiki><<PAUSE>></nowiki>'''

'''Let us switch to the slides.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display Slide

'''Single Quote'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| * '''Single quotes''' preserves the literal meaning of each character of the given string.
* It is used to turn off special meaning of all characters.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Switch to terminal>>'''Type '''echo 'Username is $USER'>> press Enter'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Switch to '''Terminal.'''

'''T'''ype '''echo space open single quote Username space is space dollar sign ''in capitals USER'' close single quote'''

and Press '''Enter'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Output

Highlight:

'''Username is $USER . '''

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The output is '''Username is $USER'''

In this example, it prints all the characters which appear within the '''single quotes.'''

It does not substitute the value of''' variable $USER'''

'''<nowiki><<PAUSE>></nowiki>'''

'''Switch back to the slides.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Display Slide'''

'''Backslash'''

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| * '''Backslash''' removes the special meaning from a single character
* It is used as an '''escape character''' in '''BASH'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Switch to terminal>>'''Type '''echo ''Username is \$USER''>> press Enter'''

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Switch to '''Terminal. '''

Type '''echo space open double quote Username space is space backslash dollar sign ''in capitals USER'' close double quote '''

Since we have given double quotes, we expect the '''echo''' command to display the username.

Let's try this command; so press '''Enter.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Output:'''

'''Highlight'''

'''Username is $USER '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The output is '''Username is $USER'''

In this example the''' backslash '''removes the special meaning of ('''Dollar''') '''$ '''symbol.

'''$USER '''is just treated as a string without any special functionality.

'''<nowiki><<PAUSE>></nowiki>'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"|
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This brings us to the end of this tutorial.

Let us switch back to slides and summarize.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display slide

Summary
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| In this tutorial we learnt,

* '''Command line arguments'''
* Functionality of '''Double quote''', '''Single quote '''and '''Backslash'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display Slide

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Watch the video available at the link shown below

It summarises the Spoken Tutorial project

If you do not have good bandwidth, you can download and watch it

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display Slide

Spoken Tutorial Workshops
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The Spoken Tutorial Project Team

Conducts workshops using spoken tutorials

Gives certificates to those who pass an online test

For more details, please write to

contact@spoken-tutorial.org

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Display Slide

Acknowledgement
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Spoken Tutorial Project is a part of the Talk to a Teacher project

It is supported by the National Mission on Education through ICT, MHRD, Government of India

More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Keep the same narration as Bash-1 and Bash-2 scripts for consistency.''Reply to nancy (26/06/2013, 11:35): "..."''

Resolved

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The script has been contributed by FOSSEE and spoken-tutorial Team.

And this is Ashwini Patil from IIT Bombay signing off.

Thank you for joining.

|}

BASH/C2/Command-Line-arguments-and-Quoting/English - Revision history

Gaurav at 04:54, 16 July 2015

Nancyvarkey at 17:28, 2 May 2014

Ashwini at 06:02, 2 May 2014

Ashwini: Created page with ''''Title of script''':''' Command line arguments and Quoting''' '''Author: '''FOSSEE and spoken-tutorial team '''Keywords: '''Video tutorial,''' '''Command Line Arguments, Sing…'

@@ Line 387: / Line 387: @@
 * '''Double quote '''substitutes the value of '''variables''' and '''commands'''
 * Example: '''echo “Username is $USER”'''
-* It displays your '''username '''on the system.
+* It displays the '''username '''on the system.
 |-