Script Arguments

Core Idea

Arguments let one script handle different inputs.

Inside a shell script:

• $1 is the first argument.
• $2 is the second argument.
• $# is the number of arguments.
• "$@" means all arguments, preserving each one separately.

Practice Alone

Create a scratch script:

mkdir -p ~/scripts
micro ~/scripts/args.sh

#!/bin/bash
set -euo pipefail

printf 'count=%s\n' "$#"
printf 'first=%s\n' "${1:-missing}"

Run it with different inputs:

bash ~/scripts/args.sh
bash ~/scripts/args.sh makers
bash ~/scripts/args.sh "two words"

Watch Out

• $1 is empty when no first argument exists unless strict mode turns that into an error.
• Use a guard before relying on required arguments.
• Quote positional parameters: "$1", not $1.

Done When

You can write a script that behaves differently based on its arguments.

Docs Pointers

• Read bash, printf, quoting, and shell scripting.