Nancyvarkey at 02:32, 8 February 2014

2014-02-08T02:32:19Z

Nancyvarkey at 16:07, 1 February 2014

2014-02-01T16:07:50Z

Ashwini: Created page with ''''Title of script: Case statement in Bash''' '''Author:''' Lavitha Pereira '''Keywords: Video tutorial, Bash shell, Case statement''' {| style="border-spacing:0;" | style="b…'

2014-01-28T06:47:42Z

Created page with ''''Title of script: Case statement in Bash''' '''Author:''' Lavitha Pereira '''Keywords: Video tutorial, Bash shell, Case statement''' {| style="border-spacing:0;" | style="b…'

New page

'''Title of script: Case statement in Bash'''

'''Author:''' Lavitha Pereira

'''Keywords: Video tutorial, Bash shell, Case statement'''

{| style="border-spacing:0;"
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 1
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Dear friends,

Welcome to the spoken tutorial on '''Case statement in Bash.'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 2
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| In this tutorial, we will learn

* Importance of '''case statement'''
* Syntax of '''case statement'''
* with an Example

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 3'''Prerequisites'''

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| To follow this tutorial, you should have knowledge on:

'''Basics of Shell Scripting''' in''' BASH.'''If not, for relevant tutorials please visit our website which is as shown,'''(http://www.spoken-tutorial.org)'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 4

System requirements
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| For this tutorial I am using''' Ubuntu Linux''' 12.04''' Operating System''' and

'''GNU BASH''' version 4.1.10

Please note,''' GNU Bash''' version 4 or above is recommended to practice this tutorial.

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 5

Case Statement

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| * The '''Bash '''shell has two forms of conditional statements.
* These are the '''if statement''' and the '''case statement. '''
* '''Case statement '''can be alternately used in place of '''if-else statement'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 6

Case statement

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| * The '''case''' statement is preferred when there are many items to select from.<br/>

* It is usually used to implement '''menus''' in a script.

|-
| style="border-top:none;border-bottom:1pt solid #000001;border-left:1pt solid #000001;border-right:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 7

Case Statement

Syntax:

case $VARIABLE inmatch_1) commands

<nowiki>;;</nowiki>match_n) commands

<nowiki>;;</nowiki><nowiki>*) command_to_execute_by_default</nowiki>

<nowiki>;;</nowiki>esac
| style="border-top:none;border-bottom:1pt solid #000001;border-left:1pt solid #000001;border-right:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| '''case''' space '''dollar VARIABLE''' space '''in'''

'''match_1 close round brackets space'''

'''commands''' and '''semicolon twice'''

'''match_n close round bracket space'''

'''commands''' and '''semicolon twice'''

'''asterisk close round bracket space'''

'''command_to_execute_by_default''' and '''semicolon twice'''

'''esac'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 8

Working Of '''Case '''Statement

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| The '''VARIABLE '''is compared to '''match_1.'''

If it does not match, it moves on to the next case which is '''match_n.'''

It will check if any one of these strings matches '''VARIABLE. '''

If yes, then all the commands until the double''' semicolon (;;) '''are executed.

|-
| style="border-top:none;border-bottom:1pt solid #000001;border-left:1pt solid #000001;border-right:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display slide 9

Working Of '''Case '''Statement
| style="border-top:none;border-bottom:1pt solid #000001;border-left:1pt solid #000001;border-right:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| If none match''' VARIABLE''', the commands associated with the '''asterisk '''are executed.

It is the default '''case '''condition because the '''asterisk '''will match all strings.

'''esac''' marks the end of '''case block.'''

|-
| style="border-top:none;border-bottom:1pt solid #000001;border-left:1pt solid #000001;border-right:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"|
| style="border-top:none;border-bottom:1pt solid #000001;border-left:1pt solid #000001;border-right:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Let us understand '''case statement''' with an example.

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Terminal:'''gedit case.sh'''
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| I have already typed the program.So, I will open the file''' case.sh'''

The program prints a warning message when the disk space reaches a certain limit.

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| '''<nowiki>[Highlight]</nowiki>'''

'''<nowiki>#!/usr/bin/env bash</nowiki>'''
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| This is the''' shebang line.'''

The location of '''bash '''is different in other '''Linux''' flavours like '''CentOS, RedHat etc.'''

Previously used '''/bin/bash '''points directly to the''' binary file'''.

'''env''' used here, abstracts the true location where '''bash''' is located.

This '''Shebang '''line improves the portability of the script on any '''GNU/Linux''' system.

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| space=`df -h | sort -rk5 | awk 'FNR == 2 {print $5}' | cut -d "%" -f1 `
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| '''df -h displays disk space''' usage in human readable form.

The output is piped to '''sort -rk5''', which sorts the fifth column in reverse order.

The output is then passed to '''awk 'FNR == 2 {print $5}'''' which extracts the fifth field of the second line.

Eventually, the output is passed to '''cut -d “% -f1” '''to strip out '''% sign.'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| case $space in
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| This is the first line of '''case statement.'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| <nowiki>[0-6][0-9]) </nowiki>

echo "'''Everything is OK'''"

<nowiki>;;</nowiki>
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Here, we compare the '''space''' between 0 and 69.

If match is found, it prints

“'''Everything is OK”'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| <nowiki>[7-8][0-9] | 9[1-8]) </nowiki>

echo "Clean out. There's a partition that is $space % full."

<nowiki>;;</nowiki>
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Next, it compares the '''space''' between 70 and 89 or from 91 to 98;

If match is found, it prints

'''“Clean out. There's a partition that is $space % full.”'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| 99)

echo " Hurry. There's a partition at $space %!"

<nowiki>;;</nowiki>
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Here, it compares the '''space''' with 99.

If match is found, it prints

'''“Hurry. There's a partition at $space %!”'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| <nowiki>*) </nowiki>

echo "This is nonexistent amount of disk space..."

<nowiki>;; </nowiki>

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| This is the default case condition because the '''asterisk '''will match all strings.

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| esac

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| And this is the end of '''case statement.'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Switch to '''terminal>> '''Type''' chmod +x case.sh>>'''Press '''Enter>>'''Type''' ./case>>'''press '''Enter'''

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Now go to the''' terminal,.'''

To make the file'' ''executable, type:''' chmod space plus x space case.sh '''Press '''Enter.'''Now type

'''dot slash case.sh'''Press '''Enter.'''

|-
| style="border-top:none;border-bottom:1pt solid #000001;border-left:1pt solid #000001;border-right:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"|
| style="border-top:none;border-bottom:1pt solid #000001;border-left:1pt solid #000001;border-right:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Note that the output will vary depending on your system diskspace.

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| <nowiki>[Highlight]</nowiki>'''The output'''

'''Everything is OK '''

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| In my machine, as match is found between 0 and 69, it prints

“'''Everything is OK”.'''

Check the message printed on your machine.

You will be able to understand which '''case statement''' was executed.

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 10

'''Summary'''
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| '''Summary'''

In this tutorial we learnt,

* Importance of''' case statement'''
* Syntax of '''case statement'''
* With the disc space example

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 11

Assignment
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| As an assignment.

# Write a menu driven program for mathematical calculation

* It should take user inputs '''a '''and '''b'''
* It should ask for mathematical opertator(+,-, / and *)
* Do the calculation and
* Print the output

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 12

http://spoken-tutorial.org /What\_is\_a\_Spoken\_Tutorial

About the Spoken Tutorial Project
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| 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:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 13

Spoken Tutorial Workshops
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| 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:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 14

Acknowledgement
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| 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:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 15
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| The script has been contributed by FOSSEE and spoken-tutorial team

This is Ashwini from IIT Bombay.

Thank you for joining.

|}

@@ Line 171: / Line 171: @@
-The output is then passed to '''awk 'FNR == 2 {print $5}'''' which extracts the fifth field of the second line.
+The output is then passed to
-Eventually, the output is passed to '''cut -d “% -f1” '''to strip out '''% sign.'''
+which extracts the fifth field of the second line.
 |-

BASH/C2/Case-statement/English - Revision history

Nancyvarkey at 02:32, 8 February 2014

Nancyvarkey at 16:07, 1 February 2014

Ashwini: Created page with ''''Title of script: Case statement in Bash''' '''Author:''' Lavitha Pereira '''Keywords: Video tutorial, Bash shell, Case statement''' {| style="border-spacing:0;" | style="b…'