Bash Functions – Syntax & Examples

Bash Functions

Bash Functions – In this Bash Tutorial, we shall learn about functions in Bash Shell Scripting with the help of syntax and examples.

About Bash Functions

• Function has to be defined in the shell script first, before you can use it.
• Arguments could be passed to functions and accessed inside the function as $1, $2 etc.
• Local Variables could be declared inside the function and the scope of such local variables is only that function.
• Using functions, you may override builtin commands of Bash Shell.

Syntax of function

Any of the following two syntax could be used for defining a function in bash shell scripting.

function <function_name> {
	# function body
}

<function_name>() {
	# function body
}

<function_name>

Name of the function. Any word consisting only of alphanumeric characters and under?scores, and beginning with an alphabetic character or an under?score, can be used as a function name.

Bash Function – Example

In the following example, we will create a function named sampleFunction, and call it.

Bash Script File

#!/bin/bash

# bash function example
sampleFunction () {
	echo Hello from Sample Function.
}

sampleFunction

Output

~$ ./bash-function 
Hello from Sample Function.

Bash Function – With function keyword

In this example, we will use function keyword to define a function.

Bash Script File

#!/bin/bash

# bash function example
function sampleFunction {
	echo This is another way to define function in bash scripting.
}

sampleFunction

Output

~$ ./bash-function-2 
This is another way to define function in bash scripting.

Bash Function with Arguments

In this example, we shall learn to pass arguments to functions, and access the arguments inside the function.

Bash Script File

#!/bin/bash

# bash function example with arguments
function functionWithArgs {
	echo $1 : $2 in this $3
}

functionWithArgs "`date +"[%m-%d %H:%M:%S]"`" "Learn Functions" "Bash Tutorial" 

Output

$ ./bash-function-arguments 
[11-21 19:30:21] : Learn Functions in this Bash Tutorial

Conclusion

In this Bash Tutorial, we have learned about Bash Functions, how to define them, with examples scripts.