Bash function to validate a long option

is_long_option.sh

#!/bin/bash
#
# SPDX-License-Identifier: MIT
# Copyright © 2022 Apolo Pena

### is_long_option ###
# Description:
# Validates a long option using the below rules
# Returns 0 if $1:
# Starts with double dashes followed by any number of uppercase or lowercase letters or integers
# optionally followed by zero or more sets of a single dash that must be accompanied 
# by any number uppercase or lowercase letters
# Returns 1 otherwise
#
# Usage:
# t() {if is_long_option "$1"; then echo "$1 is a long option"; else echo "$1 is NOT a long option"; fi;}
# t '-o' # Outputs: -o is NOT a long option
# t '--valid' # Outputs: --valid is a long option
# t '-not-valid' # Outputs: -not-valid is NOT a long option
# t '--save-file' # Output --save-file is a valid long option
is_long_option() {
  [[ $1 =~ ^--[a-zA-Z0-9]+(-[a-zA-Z0-9]+)*$ ]] && return 0 || return 1
}