Difference between revisions of "BASH/C3/Arrays-and-functions/English"

• To pass an array to a function
• Use of exit statement in a function
• Use of return statement in a function
• With the help of some examples

You should also have knowledge of

arrays and if statement in BASH.

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

System requirements

• Ubuntu Linux 12.04 Operating System and
• GNU BASH version 4.2

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

{

Open curly bracket opens the function definition.

array=($@)

#Takes array name as variable

Basically, it is used to print all arguments passed to a function.

Dollar At sign within round brackets stores array elements in variable 'array'.

#displays all element of an array

This line of code displays all the elements of an array.

#displays the 2nd element

return 0

}

This line of code displays the second element of the array.

operating_systems=(Ubuntu Fedora Redhat Suse)

Pass an array to a function

Syntax:

function_name ${array_name[@]}

function_name space dollar opening curly brace array_name within square bracket 'At sign' closing curly brace

array_display ${colors[@]}

White, green, red and blue

Here, array 'colors' is passed to the function 'array_display'.

chmod +x function_array.sh>>Press Enter

Press Enter.

./function_array.sh>>Press Enter

Press Enter.

[Output]

Array elemnts are: Ubuntu Fedora Redhat Suse

Second element is: Fedora

Array elements are: White green red blue

Second element is: green

And the second array element of 'operating_systems' and 'colors' are also displayed.

'return' and 'exit' statement in functions

Return and exit in functions

• The return statement will return to the script from where it was called.

exit:

• exit statement will end the entire script from where it is encountered.

#!/usr/bin/env bash

If the two variables are equal, then commands in 'if' are executed.

return 0

#Returns to main program

This is return function.

return 0 moves the control from function to main program with status code 0(zero).

echo "This will not appear"

}

{

If the two variables are equal, then the commands in 'if' are executed.

}

echo "This line is not displayed"

Anything after 'exit' will not be executed.

chmod +x return_exit.sh>>Press Enter

Press Enter.

dot slash return underscore exit dot sh

Press Enter.

[Output]

This is return function

We are in main program

This is exit function

Now, let us understand the flow of the program.

[Highlight program and explain]

1. The control will be in main program, which is the script itself.
2. The control goes to 'return_function' because of the function call.
3. As the two variables are equal, it displays the message "This is return function"
4. Then it encounters return 0. And the control flows from function to the statement below the function call, in the main program.
5. Then it displays the message "We are in main program"
6. After that, the control goes to 'exit_function' because of the function call.
7. As the two variables are equal, it displays the message "This is exit function"
8. Then it encounters exit 0. This will terminate the program.
9. Any statement after exit will not be executed.
10. Also, the statement:

"This line is not displayed" `

will not be executed.

Let us now summarise.

Summary

• To pass an array to a function
• Use of exit in a function
• Use of return in a function
• With the help of some examples

Assignment

Write a program,

• Where a function adds all the elements in an array
• The function should display the sum of elements.
• Make 2 function calls with array elements (1, 2, 3) and (4, 5, 6)

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