Bash function to display usage and exit

################################################################################
# Function:     usage_exit
# Description:  Prints the usage message for this script and then exits
# Arguments:    $1 :- Exit code; defaults to 1
# Outputs:      Prints description of how to call this script
function usage_exit {
    local exit_code=1

    if [[ ${1-} =~ ^[0-9]+$ ]]; then
        exit_code="$1"
    fi

    cat << EOT
Usage: $(basename "$0") [options]...
    -u|--user       <val>   (Required) The owner of the generated file
    -d|--destdir    <val>   (Required) The dir into which to save the new file
    -r|--remove             Causes previous files to be removed
    -v|--verbose            Displays verbose output
    -h|--help               Displays this message and aborts the script

NOTE: The <user> and <destdir> arguments are mandatory and *must* be supplied

EOT
    exit "${exit_code}"
}