A simple way to output command usage for shell scripts

usage_example.sh

#!/bin/bash

# A one line description of what the command does
#
# Usage:
# commandName
#  what this command does with no arguments
# commandName --argument [--optionalArg=value]
#  what this command does with these arguments. one of them is optional.
#
#  options:
#   --someOption='val' : This option can apply to any invoation of the command.

function usage { 
    usageEnd=$((LINENO - 2))
    sed -n "2,${usageEnd}p;${usageEnd}q" "${0}" | sed 's/^#//'
}

# The usage function should be at the top of the file immediately after the usage comment.
# The sed one liner will output the comment and strip off the hash signs.
usage