Reusability
Write once, use many times.
Shell Script · Function in Shell Scripting
Shell Scripting · Lesson 14
Function in Shell Scripting
Create reusable functions in shell scripts. Modular programming concept. Reduce duplicate code. Industry standard scripting method.
What is a Function?
A function is a reusable block of code designed to perform a specific task. Functions help reduce repetition and improve readability.
Why Use Functions?
Maintainability
Easier to update and debug code.
Clean Code
Improves readability and structure.
Types of Functions
- Simple functions (no arguments)
- Functions with arguments
- Functions with return status
- Functions using local variables
Function Examples
1. Basic Function Definition
A simple function that prints a message.
terminal — bash
functionsgreet() {
echo "Hello from function"
}
greet
2. Function with Arguments
Functions can accept parameters using $1, $2, etc.
terminal — bash
functionsgreet() {
echo "Hello $1"
}
greet "Jay"
3. Return Value from Function
Functions can return a status using return.
terminal — bash
functionscheck_number() {
if [ $1 -gt 10 ]; then
return 0
else
return 1
fi
}
check_number 15
echo "Return status: $?"
4. Local vs Global Variables
Local variables exist only inside the function.
terminal — bash
functionsmyfunc() {
local msg="Inside function"
echo $msg
}
myfunc
echo $msg
Best Practices
Function Best Practices
- Use meaningful function names.
- Keep functions small and focused.
- Use local variables to avoid conflicts.
- Return status codes for success/failure.
Practice Task – Functions
- Create a function to add two numbers.
- Create a function to check if a number is even or odd.
- Create a function to print system info.
Next lesson: Script Arguments ($1, $2, $@)