Difference between revisions of "BASH/C3/More-on-functions/English-timed"

|Welcome to the spoken tutorial on '''More on functions '''

| In this tutorial, we will learn

|To pass an '''argument''' to a '''function '''

|Define '''local variable''' within a '''function''' and

|Define '''global variable''' in a '''function'''

|With the help of some examples  

| To follow this tutorial you should have knowledge of '''Shell Scripting''' in''' BASH.'''

|If not, for relevant tutorials please visit our website which is as shown,'''(http://www.spoken-tutorial.org)'''

| For this tutorial I am using''' '''

|'''Ubuntu Linux''' 12.04''' '''Operating System

|'''GNU BASH''' version 4.2

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

| Let us first learn how to pass an '''argument''' to a '''function,''' and its usage.

| Let me open a file ''''function_(underscore) parameters.sh''''

| Our '''function name''' is '''say_(underscore)welcome'''

|Open curly bracket opens the '''function definition.'''

| '''$(Dollar)1 '''is the first '''positional parameter'''

|'''$(Dollar)2 '''is the second '''postional parameter'''

| Close curly bracket closes the''' function definition.'''

| Here, the function ''''say_welcome'''' is called with '''arguments'''.

|The syntax is, '''function name''' i.e. '''say welcome ''' '''...'''followed by the '''arguments '''within double quotes, i.e. '''Bash''' and '''learning.'''

| In a similar manner, I will call the same '''function''' with a different set of '''arguments. '''So, I have'''say_welcome space''' within double quote '''functions in''' space and within double quote '''Bash'''.

| Save the file and go to the terminal.

| Type '''chmod space plus x space function underscore parameters dot sh'''

| Type '''dot slash function underscore parameters dot sh'''

| We see that the positional '''parameters''' were substituted by the '''arguments''' passed to a '''function'''.

| '''Dollar 1($1) '''was substituted by the string''' Bash''' and '''Dollar 2($2) '''with''' learning.'''

| Then again, '''Dollar 1($1) '''was substituted by''' functions in''' and '''Dollar 2($2) ''' with '''Bash.'''

| It's value will be valid within the '''function''' in which it is defined.

| '''Local variables''' are declared using keyword '''local'''

| '''Global variable'''

| The value of a '''global variable''' can be accessed throughout a '''Bash '''script.

| Let me open a file named '''function_(undescore)local.sh''''

| Function name is '''say_(underscore) hello'''

| Here, '''variable''' '''first_name '''is declared with '''keyword''' '''local.'''

|Which means, its value will be valid within the function '''say_hello '''only.

| A '''variable '''declared without any keyword,is treated as a '''global variable'''.

|So, the '''variable last_name '''can be accessed throughout the script.

|'''middle_name '''  

 

|And '''last_name'''

| Now, here the variable '''middle_name ''' is declared without keyword. So, its value will be '''global ''' throughout the script.

| Once again, we will call the '''function '''here.

| We pass two '''arguments''' to this''' function call''', namely, '''“Pratik” '''and''' “Patil”.'''

| These '''echo statements''' will display the value of variables  

| '''$first_name, '''

 

| '''$middle_name '''and '''$last_name'''

| Please keep in mind that '''variable first_name '''is a '''local variable.'''

| Save the file and go to the '''terminal.'''

| Type '''chmod space plus x space function underscore local dot sh'''

| Type '''dot slash function underscore local dot sh'''

| The first line of output displays the message '''Hello Pratik K Patil.'''

| Here, the variable '''first_name '''that contains value '''Pratik''' is '''local'''.

| Which means the value is limited to the '''function'''.

| '''middle_name '''and''' last_name '''are printed as they are '''global''' '''variables.'''

|Let us now summarise.

| In this tutorial, we learnt

|To pass '''arguments''' to a''' function '''.To declare '''Local variable '''in a '''function'''

|To declare '''Global variable '''in a '''function'''. with the help of a few examples

| As an assignment.

|Write a program,

 

| Where the '''function''' accepts two '''arguments'''. The '''function''' should multiply the two '''arguments'''.

| Make 3 '''function calls''' with '''arguments''' (1, 2), (2, 3) and (3, 4)

| It summarises the Spoken Tutorial project.If you do not have good bandwidth, you can download and watch it.

| The Spoken Tutorial Project Team.Conducts workshops using spoken tutorials. Gives certificates to those who pass an online test

| 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

|This is Ashwini Patil from IIT Bombay signing off.Thank you for joining.