Book Image

Linux Shell Scripting Essentials

Book Image

Linux Shell Scripting Essentials

Overview of this book

Table of Contents (15 chapters)
Linux Shell Scripting Essentials
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Using functions and positional parameters


Similar to other programming languages, function is a way to write a set of actions once and use it multiple times. It makes the code modular and reusable.

The syntax of writing a function is as follows:

function function_name
 {
  # Common set of action to be done
 }

Here, function is a keyword to specify a function and function_name is the name of the function; we can also define a function in the following ways:

function_name()
{
  # Common set of action to be done
}

The actions written within curly braces are executed whenever a particular function is invoked.

Calling a function in bash

Consider the following shell script that defines the my_func()function:

#!/bin/bash
# Filename: function_call.sh
# Description: Shows how function is defined and called in bash

# Defining my_func function
my_func()
{
  echo "Function my_func is called"
  return 3
}

my_func # Calling my_func function
return_value=$?
echo "Return value of function = $return_value...