User-friendly Bash script template

Sometimes you need a user-friendly interface for scripts. Using raw ARG0, ARG1… is messy. Here’s a clean example of parsing arguments like -h or -a=one in Bash.

This script validates arguments, provides help output, and sets defaults for boolean and string options. It’s easy to extend for more flags.

script.sh

#!/bin/bash -e

for i in "$@"
do
  case $i in
    -h|--help)
      cat <<'EOF'

-a --a-arg      - arg A '^[a-z]+$'

EOF
      exit 1
      shift
      ;;

    -a=*|--a-arg=*)
      CMD_arg="${i#*=}"
      shift
      ;;

    -b|--bool)
      CMD_bool=True
      shift
      ;;

    *)
      ;;
  esac
done

if [[ ! ${CMD_bool} ]]; then
  var_bool=False
else
  var_bool=${CMD_bool}
fi

if [[ ${CMD_arg} =~ ^[a-z]+$ ]]; then
  var_arg=${CMD_arg}
else
  echo "Wrong '-a' use '^[a-z]+$'"
  echo "Use -h|--help for help"
  exit 1
fi

echo "-a |${var_arg}|"
echo "-b |${var_bool}|"

exit 0

Examples

[root@b398b ~]# ./bash.sh -h
-a --a-arg      - arg A '^[a-z]+$'

[root@b398b ~]# ./bash.sh -a
Wrong '-a' use '^[a-z]+$'
Use -h|--help for help

[root@b398b ~]# ./bash.sh -a=one
-a |one|
-b |False|

[root@b398b ~]# ./bash.sh -a=1
Wrong '-a' use '^[a-z]+$'
Use -h|--help for help

[root@b398b ~]# ./bash.sh -a=one -b
-a |one|
-b |True|

Human Logic, AI Syntax... Note on Content: I'm a Systems Engineer, not a native English writer. To ensure my technical ideas are clear and accessible, I use AI tools to polish the grammar and style. The workflow is simple: I provide the logic, the code, and the real-world experience. The AI handles the "English-to-Human" translation layer. If you find a bug, that's on me. If you find a perfectly placed comma, that's probably the AI.