Ashwini: Created page with ''''Title of script''': '''Basics of Shell Scripting ''' '''Author: '''FOSSEE and Spoken-tutorial Team '''Keywords: '''Video tutorial,''' '''Bash, Shell, System variables, User …'

2013-07-26T07:47:58Z

Created page with ''''Title of script''': '''Basics of Shell Scripting ''' '''Author: '''FOSSEE and Spoken-tutorial Team '''Keywords: '''Video tutorial,''' '''Bash, Shell, System variables, User …'

New page

'''Title of script''': '''Basics of Shell Scripting '''

'''Author: '''FOSSEE and Spoken-tutorial Team

'''Keywords: '''Video tutorial,''' '''Bash, Shell, System variables, User defined variables, getting user input via keyboard.

{| 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 '''Basics of Shell Scripting.'''

|-
| 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

* '''System variables '''
* '''User defined variables''' and
* Accepting user input via keyboard

|-
| 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 '''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

'''Variables'''

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| * '''Bash variables''' provide temporary storage for information.
* These '''variables '''can be used within the lifespan of the program.
* There are two types of variables

# '''System variables'''
# '''User defined variables '''

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

'''System Variables'''

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''System variables '''are created and maintained by''' Linux Bash Shell''' itself.

They are defined by Capital letters.

Commonly used '''system variables '''are

* '''BASH_VERSION, '''
* '''HOSTNAME, '''
* '''HOME etc'''

|-
| 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;"| Terminal:

'''set>>'''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 type '''set''' and press '''Enter.'''

This will display all the '''system variables'''.

|-
| 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;"| Alternately, you can type '''env '''or''' printenv,''' to view all the '''system variables.'''

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

'''echo "$HOSTNAME">> '''Press '''Enter'''

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

'''echo space opening double quote dollar sign HOSTNAME closing double quote'''

and press '''Enter.'''

The '''hostname''' of the system will be displayed.

|-
| 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 let's find out the full path of '''home '''directory.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| On terminal type>>'''echo "$HOME">> '''press '''Enter'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| So, type

'''echo space open double quote dollar sign HOME close double quote'''

and press '''Enter.'''

The full path of user's '''home''' directory will be displayed.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| On terminal type>>'''echo "HOME">> '''press '''Enter'''

'''Output:'''

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

'''echo space open double quote HOME close double quote'''

and press '''Enter.'''

This will display only the '''HOME''' not the value of '''HOME''' variable.

|-
| 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;"| So it is neccessary to use '''dollar sign '$' '''at the beginning of every variable, to display its value.

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

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

'''User Defined Variables'''

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

* These '''variables''' are created and maintained by users.
* It is always a good idea to avoid '''uppercase''' for the names of '''user defined variables'''.
* This makes it easy to differentiate between '''user defined '''and '''system variables'''.

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

'''username=sunita>> '''Press''' Enter'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| On the '''terminal '''type:

'''username equal to sunita '''

Please note that there should not be any blank space between '''username''', '''equal to '''sign and '''sunita'''.

Now press '''Enter.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Type >>'''echo "$username">> '''Press '''Enter'''

Highlight output:

'''sunita'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Now, to display the value of variable '''username'''

type:

'''echo''' space '''open double quote dollar sign username close double quote''' and press '''Enter'''

This will display '''sunita '''on your '''terminal.'''

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

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

Unset

'''syntax :'''

'''unset variablename'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The value of a variable can be unset by using the '''unset '''command.

The syntax for this is '''unset space variablename'''

|-
| 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's use the previous example where '''username '''is our variable.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Switch to '''Terminal'''>> type '''unset username>> '''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 the '''terminal '''and type

'''unset space username '''

and press '''Enter.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Type '''echo $username>> '''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 type

'''echo space dollar sign username '''

and press '''Enter.'''

Nothing will be displayed on the '''terminal'''.

This means that the value of '''variable username''' has been removed.

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

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

'''Global and Local Variables'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| * In '''Shell '''script,''' user defined variables''' can be declared '''globally''' and '''locally. '''
* By default, all '''variables''' are '''global.'''
* This means, their values remain the same inside and outside the '''function'''.

|-
| 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 us learn how to declare '''variables''' '''globally '''and''' locally.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Switch to '''terminal'''>>'''gedit g_variable.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;"| Switch to the '''terminal '''and type

'''gedit''' '''space g_variable.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;"| Type the code as shown, in your''' g_variable.sh '''file.

|-
| 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;"| Highlight '''<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;"| The first line, with the '''hash '''and '''exclamation '''symbols, is a '''shebang''' or a '''bang''' line.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight '''username=sunita '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''username=sunita '''is the '''userdefined variable '''and it is declared '''globally.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight '''echo "outside function: $username" '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''echo '''will display the string '''outside function: '''

And

'''dollar username''' will print the value of the variable '''username.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight '''func() '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This is how a '''function''' is defined in '''BASH''' script.

We will discuss about''' functions '''in detail, in later tutorials.

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

'''{ '''

'''echo "inside function: $username"'''

'''} '''
| 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 body of the '''function'''.

Here another message '''inside function '''will be displayed, along with the value of '''username.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight '''func '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Here, we call the function '''func.'''

This is our code. Now let's execute it.

|-
| 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 g_variable.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;"| Switch to the '''Terminal. '''

First we need to make our file executable.

So type

'''chmod''' '''space plus x space g_variable.sh'''

and press '''Enter'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Type '''./g_variable.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;"| Now let us execute this '''Shell '''script by typing

'''dot slash g_variable.sh'''

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:'''

'''outside function: sunita '''

'''inside function: sunita '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Observe the output displayed.

Outside the function, '''username '''takes the value '''sunita.'''

Inside the function also, '''username''' takes the same value i.e. '''sunita'''.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Switch to the program code in '''gedit'''.
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This is because '''username''' was declared '''globally '''outside the function.

'''<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;"| Next, let us learn how to declare a variable '''locally'''.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Switch to '''terminal'''>>'''gedit g_variable.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;"| Switch to the '''terminal '''and type

'''gedit''' '''space l_variable.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;"| Type the code as shown, in your''' l_variable.sh '''file.

|-
| 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;"|
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The code is the same as before, except for an extra line of code inside the function.

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

'''local username=jack '''

'''echo "inside function: $username" '''

'''} '''

'''func '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Inside the '''function''' block, we have a line,

'''local''' '''space username equal to jack'''

|-
| 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 assigns a new value for the variable '''username locally'''.

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

|-
| 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 l_variable.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;"| Switch to the '''Terminal. '''

Let's make our file executable by typing

'''chmod''' '''space plus x space l_variable.sh'''

and press '''Enter.'''

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

'''dot slash l_variable.sh'''

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:'''

'''outside function: sunita '''

'''inside function: jack'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Outside the '''function''', '''username''' takes the value '''sunita.'''

Whereas inside the '''function''', '''username''' takes the value '''jack'''.

This is because '''username''' is assigned this value '''locally,''' within the function.

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

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

'''Getting user input via keyboard'''

| 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 quickly see how to get user input via keyboard.

The '''read''' command is used to accept input from the keyboard.

It can also be used to assign an input value to a '''user defined variable'''.

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

Syntax

'''read -p "PROMPT " '''

'''man read'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The syntax of '''read '''command is

'''read space hyphen p space open double quote PROMPT close double quote '''

Press '''Enter'''

Now type,

'''man read'''

Please note that '''PROMPT''' is just a string, that waits for user input.

You may replace it with your own string.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Switch to '''terminal'''>>'''gedit read.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;"| Switch to the '''terminal '''and type

'''gedit''' '''space read.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;"| Type the code as shown, in your''' read.sh '''file.

|-
| 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;"|
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| In this example, input is given from the keyboard by the user.

|-
| 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 the '''shebang''' or a '''bang''' line.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''read -p "Enter username: " username '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Here '''-p '''displays the prompt, without a newline and takes input from the keyboard.

The user input will be stored in the variable '''username'''.

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

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''echo '''command displays the message '''Hello''' and the name entered by the user, via the keyboard.

|-
| 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>'''

So, let's switch to the '''Terminal '''and execute this 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 read.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;"| First, let's make our file executable by typing

'''chmod''' '''space plus x space read.sh'''

and press '''Enter.'''

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

'''dot slash read.sh'''

and press '''Enter.'''

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

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

I will type '''ashwini a'''nd press '''Enter.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Hello ashwini '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The message''' Hello ashwini''' is displayed.

'''ashwini''' was assigned as an input value to the user defined variable '''username.'''

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

|-
| 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,

* '''System variables '''
* '''User defined variables'''
* Accepting user input via keyboard

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

'''Assignment'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| # Write a simple '''Bash''' program to get the following system variables

* '''pwd '''
* '''logname'''

# Write a simple '''Bash''' program

* To ask '''username''' from user''' '''
* To exit the program, if user does not enter anything, within 10 seconds
* {Hint: '''read -t 10 -p}'''

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

|-
| 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;"|
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The script for this tutorial was written by the FOSSEE Team, IIT Bombay.

And this is Ashwini from IIT Bombay.

Thank you for joining.

|}

BASH/C2/Basics-of-Shell-Scripting/English - Revision history

Ashwini: Created page with ''''Title of script''': '''Basics of Shell Scripting ''' '''Author: '''FOSSEE and Spoken-tutorial Team '''Keywords: '''Video tutorial,''' '''Bash, Shell, System variables, User …'