Function arguments ($1, $2 inside function) in Bash Scripting - Step-by-Step Execution

Concept Flow - Function arguments ($1, $2 inside function)

Define function

↓

Call function with args

↓

Inside function: $1, $2 hold args

↓

Use $1, $2 in commands

↓

Function ends, return to caller

The function is defined, then called with arguments. Inside, $1 and $2 hold the first and second arguments, used in commands.

Execution Sample

Bash Scripting

greet() {
  echo "Hello, $1 and $2!"
}

greet Alice Bob

Defines a function greet that prints a hello message using two arguments passed when calling it.

Execution Table

Step	Action	Value of $1	Value of $2	Output
1	Define function greet	-	-	-
2	Call greet with Alice Bob	Alice	Bob	-
3	Inside greet: echo message	Alice	Bob	Hello, Alice and Bob!
4	Function ends, return to caller	-	-	-

💡 Function completes after printing the message.

Variable Tracker

Variable	Start	After call	Inside function	After function ends
$1	-	-	Alice	-
$2	-	-	Bob	-

Key Moments - 2 Insights

Why does $1 hold 'Alice' inside the function?

Because when the function is called (see execution_table step 2), the first argument 'Alice' is assigned to $1 inside the function.

What happens if the function is called with only one argument?

Then $2 will be empty inside the function, so using $2 will produce no output or an empty string (not shown in this trace).

Visual Quiz - 3 Questions

Look at the execution table, what is the value of $2 at step 3?

A Hello

B Alice

C Bob

D Undefined

💡 Hint

Check the 'Value of $2' column at step 3 in the execution_table.

At which step does the function greet get called with arguments?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the step describing the function call in the execution_table.

If we call greet with 'John' only, what will $2 be inside the function?

A Empty string

B Error

C John

D Undefined variable

💡 Hint

Refer to key_moments about missing second argument behavior.

Concept Snapshot

Function arguments in bash are accessed inside functions as $1, $2, etc.
$1 is the first argument, $2 the second.
When calling a function, pass arguments separated by spaces.
Inside the function, use $1, $2 to refer to them.
If fewer arguments are passed, missing ones are empty strings.

Full Transcript

This visual trace shows how bash function arguments work. First, a function named greet is defined. Then it is called with two arguments: Alice and Bob. Inside the function, $1 holds 'Alice' and $2 holds 'Bob'. The function uses echo to print a message including these arguments. After printing, the function ends and returns control to the caller. If fewer arguments are passed, the missing ones become empty inside the function. This helps understand how to pass and use arguments in bash functions.