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Functions in Bash Script

A function is a small piece of code or command which can be used multiple times in a script. A function in bash can be created using the function keyword. It is one of the best ways to make a Bash script modular, as small chunks of code are easier to develop and maintain.

The syntax for function creation.

To define a function, you can use either one of two forms, as given below.

# First form
 function functname{
 shell commands
}

# Second Form
 functname ()
 {
 shell commands
}

There is no functional difference between the two. When we define a function, we are telling the shell to store its name and definition in memory. If we want to run the functions later, we can just type in its name followed by any arguments, as if it were a shell script.

Simple Function in Shell

Let’s create a simple script named helloWorld.sh

#!/bin/bash

function helloWorld(){
echo "Hello World!"
}

#Calling Function
helloWorld
helloWorld

Make the script executable by using chmod u+x hello_world.sh and run the script.

~$ chmod u+x helloWorld.sh
:~$ ./helloWorld.sh
Hello World!
Hello World!

Functions with Parameters

Let’s create a bash script named function_with_param.sh which takes parameters.

#!/bin/bash

## Function which takes two parameters
function printMyName(){
first_name=$1
last_name=$2
echo "My Name is $first_name $last_name"

}

printMyName Nitendra Gautam

~$ chmod u+x  function_with_param.sh 
 :~$ ./ function_with_param.sh 
 My Name is Nitendra Gautam
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