Shell script skeleton

3s.sh

#!/usr/bin/env bash
#
# Name of the Script
# Your Name
#
# Description of the script. 
#
# Usage:
#
# $> yourscript -a[f1|f2] -b
#

set -Eeuo pipefail

readonly SCRIPT_NAME=${0##*/}

# Print usage
function help() {
  cat <<END;
USAGE:
  $SCRIPT_NAME -a [f1|f2]
END
  exit
}

# Prints messages to STDERR and exits with a non-zero status code
function err() { 
    echo -e "\033[0;31mERROR:\033[0m ${1}" >&2;
    exit 1
}

function func_1() {
    echo "Hello from func_1!"
}

function func_2() {
    echo "Hello from func_2!"
}

function main() {
    # Reset in case `getopts` was recently used in the shell.
    OPTIND=1

    while getopts ":a:" opt; do
        case $opt in
        a)
            case $OPTARG in
            f1)
                func_1
                exit 0
                ;;
            f2)
                func_2
                exit 0
                ;;
            *)
                err "Invalid argument: -$OPTARG";
                ;;
            esac
            ;;
        \?)
            err "Invalid option";
            ;;
        :)
            err "Option -$OPTARG requires an argument.";
            ;;
        esac
    done

    shift $((OPTIND-1))

    # No more arguments. Invoke the help command
    [[ -z "$1" ]] && help
}

# Run
main "$@"

3S (Shell Script Skeleton)

This is my adapted version of z017's Shell Script Skeleton with help from this tutorial and this StackOverflow answer. It does most of what z017's script does, but the main differentiator is this is fewer lines of code and easier to understand.