Linux Fundamentals - Part 8: Bash Scripting (Functions)

Bash Function

A function is a block of code that performs a specific task.
Instead of writing the same commands over and over, you can put them inside a function and call it whenever you need.

Think of a function as a mini-program inside your script.

How to Define a Function?

The basic syntax of a Bash function looks like this:

my_function() {
  commands…
}

The name goes first, followed by (), then the body of the function inside {}.

Example:

#!/bin/bash

hello() {
  echo "Hello from a function!"
}

This defines a function called hello. It doesn’t do anything until you call it.

Calling (Using) a Function

To run a function, just write its name:

#!/bin/bash

hello() {
  echo "Hello from a function!"
}

hello

If you save this as func.sh and run:

bash func.sh 

or

./func.sh

The Output is:

Hello from a function!

Why Use Functions?

Functions help:

• Reuse code
• Organize your script into smaller pieces
• Make longer scripts easier to understand

Instead of repeating the same commands, put them inside a function and call them when needed.

Passing Arguments to Functions

Functions can get information — this is done with arguments.

Inside a function:
$1 refers to the first argument
$2 refers to the second
…and so on

Example:

#!/bin/bash

greet() {
  local name=$1
  echo "Hello, $name!"
}

greet "Kervie"
greet "Jay"

The Ouput of this code is:

Hello, Kervie!
Hello, Jay!

Returning Values

Unlike some languages, Bash functions don’t return values like functions in Python or Java do.

Instead, use echo to output results, and capture it like this:

#!/bin/bash

add() {
  local sum=$(($1 + $2))
  echo $sum
}

result=$(add 5 3)
echo "The total is: $result"

Output:

The total is: 8

This is how you get your function to “return” something useful.

Summary

Bash Function Concept	How It Works
Define a function	name() { … }
Call a function	Just type the name
Arguments	$1, $2, …
Return value	Use echo and capture with $(…)

Today, I learned how to use functions in Bash to organize and reuse code inside my scripts. I discovered how to define a function, call it, and pass arguments to make it more flexible. I also learned how Bash functions handle outputs using echo instead of traditional return values.

Tomorrow, I will focus on learning Bash Arrays and understanding how they work in scripts. I also plan to practice using both functions and arrays together to strengthen what I’ve learned.