Ashwini: Created page with ''''Title of script: Array Operations In BASH''' '''Author:''' Lavitha Pereira '''Keywords: Video tutorial, Bash shell, Array''' {| style="border-spacing:0;" | style="border:1…'

2013-08-22T07:45:45Z

Created page with ''''Title of script: Array Operations In BASH''' '''Author:''' Lavitha Pereira '''Keywords: Video tutorial, Bash shell, Array''' {| style="border-spacing:0;" | style="border:1…'

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'''Title of script: Array Operations In BASH'''

'''Author:''' Lavitha Pereira

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

{| 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;"| Welcome to the spoken tutorial on

'''Array operations in BASH '''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 2

Learning Objectives
| 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 how to

* Declare an''' Array''' and assign value to it.
* Initialize an''' Array''' during declaration

|-
| 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 3

Learning Objectives (contd.)
| 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;"| * To find length of''' '''an''' Array''' and its '''n'''th''' element'''
* To print an '''Array'''

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

'''Prerequisites'''

'''spoken-tutorial.org '''
| 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 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 #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 5

'''System Requirements'''
| 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;"| 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 #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 6

'''Array Definition'''
| 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 start with the definition of an''' Array''' and its characteristics.

* An''' Array''' is a variable with multiple values.
* The values can be of same or different types

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 7

'''Array Charactristics'''

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| * There is no maximum limit for the size of an '''array'''
* '''Array''' members need not be consecutive
* '''Array index''' always starts with''' ''' '''zero'''

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

'''Declare and assign values to an Array'''

Syntax:

'''declare -a arrayname '''
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| We will now see how to declare and assign a value to an '''Array'''.

The syntax to declare an '''Array''' is -

'''declare space hyphen `a` space arrayname'''

|-
| 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;"| '''“declare” '''keyword is used to declare an '''Array'''.

It is a built-in command in '''Bash'''.

|-
| 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 8'''

Syntax:

'''<nowiki>Name[index]='value'</nowiki>'''
| 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;"| The syntax to assign a value to an '''Array '''is-

'''Name opening square bracket index closing square bracket equal to within single quotes value.'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| === Display Slide 9 ===
=== Initialize an Array during declaration ===

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Now let see how to initialize an '''Array''' during declaration.

* '''Arrays''' can be declared and initialized at the same time.
* Each element in the list is separated by a '''space''' and is within '''parentheses'''.

|-
| 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 10 ===
=== Initialize an Array during declaration ===
Syntax:

'''declare -a arrayname=('element1' 'element2' 'element3')'''

| 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;"| The syntax is as shown

'''declare space hyphen `a` space arrayname equal-to opening round bracket within single quotes 'element1' space 'element2' space'''

''''element3' closing round bracket.'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"|
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Let us try an example.

|-
| 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;"| Press''' Ctrl+Alt+T'''
| 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;"| Open the '''terminal''' by pressing'''Ctrl+Alt+T''' keys simultaneously.

|-
| 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;"| On '''Terminal '''>>Type '''gedit array.sh'''

| 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;"| Type:

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

Now type the code as shown here into your''' array.sh '''file'''.'''

|-
| 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;"| Highlight

'''declare -a Linux=('Debian' 'Redhat' 'Ubuntu' 'Fedora')'''
| 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;"| This line declares an '''Array '''named '''Linux '''with elements -

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

|-
| 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;"| Here

'''hyphen `a` '''is''' '''a '''flag.'''

It allows us to read and assign '''values '''to''' '''an '''Array. '''

|-
| 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 switch back to the slides.

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| === Display Slide ===
=== Length of an Array and of its nth element. ===
'''<nowiki>${#arrayname[@]}</nowiki>'''
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| The length of an '''Array''' can be obtained by this code:

'''Dollar symbol opening curly bracket hash arrayname opening square bracket At sign closing square bracket closing curly bracket'''

|-
| 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 (contd.) ===
'''<nowiki>${#arrayname[n]}</nowiki>'''
| 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;"| The length of the '''nth '''element can be obtained by this code:

'''Dollar symbol opening curly bracket hash arrayname opening square bracket index number `n` closing square bracket closing curly bracket'''.

Here''' n''' is the element number, whose length is to be found.

|-
| 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 ===
=== Print the whole Array ===
Syntax:

'''<nowiki>${arrayname[@]}</nowiki>'''

| 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;"| All the elements of the '''Array''' can be printed using this syntax.

'''Dollar sign opening curlybracket Arrayname opening square bracket `At sign` closing square bracket closing curly bracket.'''

|-
| 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;"| Come back to the '''text editor.'''

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

echo -e "Total number elements in an array Linux:''' <nowiki>${#Linux[@]}</nowiki>''' \n"

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| This line will display total number of elements in the '''Array Linux'''.

'''hyphen `e` '''enables interpretation of '''backslash '''escapes.

We have included this as we have '''backslash `n` '''at the end of the line'''.'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| echo -e "The elements of array Linux are:'''<nowiki> ${Linux[@]}</nowiki>''' \n"
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Next line displays all the elements of the '''Array Linux.'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| echo -e "Third element in array Linux is:'''<nowiki> ${Linux[2]}</nowiki>''' \n"

| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| This line displays the 3rd element of the '''Array Linux.'''

Please note that an '''Array''' always starts with '''index''' '''zero.'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| echo -e "Length of third element is: $'''<nowiki>{#Linux[2]}</nowiki>''' \n"
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Lastly, this line displays the number of characters present in the 3rd element'''.'''

|-
| 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 array.sh>> '''Press''' Enter>>'''

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

Let's first make the file executable by typing'''chmod''' '''space plus x space array.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;"| Type''' ./array>> '''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;"| Now execute by typing

'''dot slash array.sh'''

Press '''Enter.'''

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

<nowiki>[Highlight]</nowiki>

'''Length of the Array Linux is: 4'''
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| The number of elements or the length of the '''Array `Linux`'''is '''four.'''

|-
| 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;"| Output:

<nowiki>[Highlight]</nowiki>

'''The elements of Array Linux are: Debian Redhat Ubuntu Fedora'''
| 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;"| The elements of''' '''the''' Array Linux''' are '''Debian, Redhat, Ubuntu, Fedora'''

|-
| 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;"| Output:

<nowiki>[Highlight]</nowiki>

'''Third Element in Array Linux is: Ubuntu'''
| 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;"| The''' '''3rd''' '''element of '''Array Linux''' is''' Ubuntu'''

|-
| 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;"| Output:

<nowiki>[Highlight]</nowiki>

'''Length of Third Element is: 6'''
| 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;"| And the number of characters in the''' third element '''is '''six, '''as expected.

<nowiki><pause></nowiki>

|-
| 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 summarize. Come back to our slides.

|-
| 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

'''Summary'''
| 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;"| In this tutorial we learnt,

* Declare and assign values to an '''Array'''
* Initialize an '''Array''' during declaration
* How to find length of''' '''an''' Array''' and length of its''' nth element''' and
* To print whole''' Array'''

|-
| style="border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Display Slide 9

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

Declare an array '''names''' of length 7 and find:

* the total number of elements
* print all the elements
* print the 5th element

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

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

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
| 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.

|}

BASH/C2/Array-Operations-in-BASH/English - Revision history

Ashwini: Created page with ''''Title of script: Array Operations In BASH''' '''Author:''' Lavitha Pereira '''Keywords: Video tutorial, Bash shell, Array''' {| style="border-spacing:0;" | style="border:1…'