How to Call a Function in Bash: Simple Syntax and Example

In Bash, you call a function simply by writing its name followed by parentheses like function_name() or just function_name. The function must be defined before you call it in the script.

Syntax

To call a function in Bash, you just write its name followed by parentheses (). You can also call it without parentheses. The function must be defined earlier in the script.

Example parts:

• function_name(): defines the function
• function_name: calls the function
• (): parentheses are optional when calling

bash

function_name() {
  echo "Hello from function"
}

function_name  # calling the function

Output

Hello from function

Example

This example shows how to define a function named greet and call it to print a message.

bash

# Define the function
greet() {
  echo "Hello, welcome to Bash functions!"
}

# Call the function
greet

Output

Hello, welcome to Bash functions!

Common Pitfalls

Common mistakes include calling a function before it is defined, forgetting parentheses in the definition, or using incorrect syntax.

Also, calling a function with parentheses is optional, but parentheses are required in the definition.

bash

# Wrong: calling before definition
# greet
# greet() {
#   echo "Hi"
# }

# Right: define first, then call
greet() {
  echo "Hi"
}
greet

Output

Hi

Quick Reference

Action	Syntax	Notes
Define function	function_name() { commands; }	Parentheses required in definition
Call function	function_name or function_name()	Parentheses optional when calling
Call before define	Not allowed	Function must be defined before calling
Pass arguments	function_name arg1 arg2	Access with $1, $2 inside function

Key Takeaways

Define your Bash function before calling it in the script.

Call functions by their name with or without parentheses.

Parentheses are required only in the function definition, not in the call.

Passing arguments to functions is done by listing them after the function name.

Avoid calling functions before they are defined to prevent errors.