BASH/C2/More-on-Arrays/English - Revision history

Ashwini at 09:46, 10 November 2014

2014-11-10T09:46:11Z

Ashwini at 09:45, 10 November 2014

2014-11-10T09:45:41Z

Ashwini at 07:35, 10 November 2014

2014-11-10T07:35:25Z

Ashwini at 07:26, 10 November 2014

2014-11-10T07:26:50Z

Ashwini: Created page with ''''Title of script: More on Arrays in BASH Shell Scripting''' '''Author:''' Lavitha Pereira '''Keywords: video tutorial, Bash shell, Array''' {| style="border-spacing:0;" | s…'

2013-08-26T05:44:33Z

Created page with ''''Title of script: More on Arrays in BASH Shell Scripting''' '''Author:''' Lavitha Pereira '''Keywords: video tutorial, Bash shell, Array''' {| style="border-spacing:0;" | s…'

New page

'''Title of script: More on Arrays in BASH Shell Scripting'''

'''Author:''' Lavitha Pereira

'''Keywords: video tutorial, Bash shell, Array'''

{| style="border-spacing:0;"
| style="border:1pt solid #000000;padding:0.097cm;"| <center>'''Visual Cue'''</center>
| style="border:1pt solid #000000;padding:0.097cm;"| <center>'''Narration'''</center>

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 1
| style="border:1pt solid #000000;padding:0.097cm;"| Welcome to the spoken tutorial on

'''More on Arrays in BASH'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 2

'''Learning Objectives'''
| style="border:1pt solid #000000;padding:0.097cm;"| In this tutorial, we will learn to

* Extract an element from an''' Array'''
* Replace an element in an''' Array'''
* Add an element to an''' Array'''
* Remove an element from an''' Array'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 4

'''Prerequisite'''

'''spoken-tutorial.org '''

| style="border: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:1pt solid #000000;padding:0.097cm;"| Display Slide 5

'''System Requirements'''
| style="border: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 practice this tutorial.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 6

'''“Extract of element from an Array”'''

| style="border:1pt solid #000000;padding:0.097cm;"| * The elements in an''' Array''' can be extracted from any position
* Here, position is the''' index number'''.
* Note that''' index number''' always starts from''' zero'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Display Slide 6

'''Syntax:'''

'''<nowiki>ArrayName[@]:position:Number of elements</nowiki>'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The syntax is as follows:

'''ArrayName opening square bracket At sign closing square bracket colon position colon Number of elements to be extracted from the position mentioned.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Let us understand with the help of an example.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;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;"| Open the '''terminal''' by pressing'''Ctrl+Alt+T''' keys simultaneously

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| On '''Terminal '''>>Type '''gedit array2.sh'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Type:

'''gedit''' space''' array2.sh''' on the''' terminal.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;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 type the code as shown here in your''' array2.sh file.'''

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

'''<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''' Shenbang line'''

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

'''declare -a Linux=('Debian' 'Redhat' 'Ubuntu' 'Fedora')'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This '''declare command '''declares an '''array '''named '''Linux '''with elements

* Debian,

* '''Redhat, '''
* '''Ubuntu '''and
* '''Fedora'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''<nowiki>echo -e "Original elements in an array Linux: ${Linux[@]} \n"</nowiki>'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This '''echo command''' will print the list of all the elements in the array.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''<nowiki>echo -e "The two elements starting from index one(Redhat): ${Linux[@]:1:2}\n"</nowiki>'''

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The next '''echo command''' will print the extracted elements.

The command

'''<nowiki>${Linux[@]:1:2}</nowiki>'''

will print two elements starting from index '''one''' which is '''Redhat.'''

|-
| 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''' chmod +x array2.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 '''Terminal.'''

First let's make the file executable by typing'''chmod''' '''space plus x space array2.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;"| Type''' ./array2.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's execute it by typing

'''dot slash array2.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;"| '''OUTPUT'''

'''<nowiki>[Highlight]</nowiki>'''

'''Original elements in an array Linux: Debian Redhat Ubuntu Fedora'''

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| We get the output as shown -

'''Original elements in the array Linux: Debian Redhat Ubuntu Fedora'''

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

'''<nowiki>[Highlight]</nowiki>'''

'''The two elements starting from index one(Redhat): Redhat Ubuntu'''

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''The two elements starting from index one(Redhat): Redhat Ubuntu'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;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 switch back to the slides

|-
| style="border:1pt solid #000000;padding:0.097cm;"| ===== Display Slide 7 =====
===== “Replace an element in an Array” =====
'''<nowiki>ArrayName[n]='NewWord'</nowiki>'''

| style="border:1pt solid #000000;padding:0.097cm;"| An existing element in an''' Array''' can be replaced using the following syntax.'''ArrayName opening square bracket n closing square bracket equal to within single quote, NewWord.'''

Here''' 'n'''' is the''' index number''' or''' element number.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;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;"| Come back to the text editor.

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

<nowiki>Linux[2]='Mandriva'</nowiki>
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''<nowiki>Linux[2]='Mandriva'</nowiki>'''

This command will replace the third element '''Ubuntu''' with '''Mandriva.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| <nowiki>echo -e "All elements after replacement: ${Linux[@]} \n"</nowiki>
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This '''echo command '''will display all elements of '''array Linux '''after replacement.Till here will execute and show.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;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;"| I did not understand this line here.''Reply to Nancy Varkey (08/08/2013, 11:13): "..."''

It says, as the script was already executed, we will not execute again, instead we will browse through its outputAs '''array2.sh '''is already executed.

We will switch to '''terminal''' and see the output.

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

'''All elements after replacement: Debian Redhat Mandriva Fedora '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This displays all elements after '''Ubuntu''' was replaced with '''Mandriva '''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;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;"| Switch to slides

|-
| style="border:1pt solid #000000;padding:0.097cm;"| ===== Display Slide 8 =====
'''“Add an element to an Array”'''

'''Syntax:'''

'''<nowiki>ArrayName=("${ArrayName[@]}" "New_word_1" "New_word_2")</nowiki>'''

| style="border:1pt solid #000000;padding:0.097cm;"| We can '''append''' an '''element''' using the following syntax -

'''ArrayName equal to opening round bracket within double quote dollar symbol opening curly bracket ArrayName opening square bracket At sign closing square bracket closing curly bracket .'''

'''space within double quote New_Word_1 space within double quote New_Word_2 closing round bracket.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;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 understand this with the help of our example.

Switch to the code file.

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

<nowiki>Linux=("${Linux[@]}" "Suse")</nowiki>
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The highlighted command will '''append '''a new '''element Suse '''to the '''array Linux'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| <nowiki>echo -e "All elements After appending Suse: ${Linux[@]} \n"</nowiki>
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Then we will '''echo '''all the elements after appending '''Suse.Again till here we can execute and show.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| So this will be executed and shown, right?

I am not clear what is intended here.The command highlighted is actual output. Previously we had 4 elements, then we added 'Suse' and the end of the list making it total of 5 elements. The output is the list of all five elements
| 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''' and see the output

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

'''All elements After appending Suse: Debian Redhat Mandriva Fedora Suse'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Here we can see all the elements after appending '''Suse '''to the '''array '''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;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, come back to the slides

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 9

'''Remove an element from an Array'''

'''unset ArrayName<nowiki>[</nowiki>Index number]'''

| style="border:1pt solid #000000;padding:0.097cm;"| An element can be removed from an''' array''' by using the following syntax -

'''Unset space ArrayName opening square bracket index number closing square bracket.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Let us switch to the code file.

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

<nowiki>unset Linux[2]</nowiki>
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Here we are using the '''unset''' '''command.'''

And''' '''we will remove''' '''the third '''element Mandriva''' from''' '''the array '''Linux.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| <nowiki>echo -e "All elements after removal of third element: ${Linux[@]} \n"</nowiki>
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Then we will '''echo''' all the elements again after the removal of '''Mandriva'''.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;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;"| Same question as before.''Reply to Nancy Varkey (08/08/2013, 11:20): "..."''

Here we have removed one element i.e. Mandriva making to count back to 4. The output will show the remaining list of elementsSwitch to '''terminal''' and observe the output

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''All elements after removal of third element: Debian Redhat Fedora Suse '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Here is the list of elements after removing '''Mandriva'''

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

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;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 summarize.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Display slide 10

'''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 learned to

* Extract an element from an''' Array'''
* Replace an element in an''' Array'''
* Add element to an''' Array'''
* Remove element from an''' Array'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 11

Assignment
| style="border:1pt solid #000000;padding:0.097cm;"| As an assignment.

# Declare an''' array''' names of length 7 and perform following operations

* extract three elements starting from index two
* Replace third element with''' 'XXX'''' and display all the elements
* Append any new name at the end of''' Array'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 12
| style="border:1pt solid #000000;padding:0.097cm;"| Watch the video available at the link shown below

It summarizes the Spoken Tutorial project

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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 13

Spoken Tutorial Workshops
| style="border: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:1pt solid #000000;padding:0.097cm;"| Display Slide 16

Acknowledgement
| style="border: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:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| The script has been contributed by FOSSEE and spoken-tutorial team.

This is Ashwini from IIT Bombay.

Thank you for joining.

|}

@@ Line 7: / Line 7: @@
 {| style="border-spacing:0;"
-| style="border:1pt solid#000000;padding:0.097cm;"|<center>'''Visual Cue'''</center>
+| style="border:1pt solid #000000;padding:0.097cm;"| <center>'''Visual Cue'''</center>
-| style="border:1pt solid#000000;padding:0.097cm;"|<center>'''Narration'''</center>
+| style="border:1pt solid #000000;padding:0.097cm;"| <center>'''Narration'''</center>
 |-

@@ Line 192: / Line 192: @@
-| style="border:1pt solid #000000;padding:0.097cm;"| An existing element in an''' Array''' can be replaced using the following syntax.'''ArrayName opening square bracket n closing square bracket equal to within single quote, NewWord.'''
+| style="border:1pt solid #000000;padding:0.097cm;"| An existing element in an''' Array''' can be replaced using the following syntax.
@@ Line 217: / Line 219: @@
 | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"|
-It says, as the script was already executed, we will not execute again, instead we will browse through its outputAs '''array2.sh '''is already executed.
+It says, as the script was already executed, we will not execute again, instead we will browse through its output as '''array2.sh '''is already executed.
 We will switch to '''terminal''' and see the output.
@@ Line 268: / Line 270: @@
 | style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| So this will be executed and shown, right?
-I am not clear what is intended here.The command highlighted is actual output. Previously we had 4 elements, then we added 'Suse' and the end of the list making it total of 5 elements. The output is the list of all five elements
+Previously we had 4 elements, then we added 'Suse' and the end of the list making it total of 5 elements. The output is the list of all five elements
 | 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''' and see the output