#!/bin/bash

{

    local self="$(readlink -f -- "${BASH_SOURCE[0]}")"

    set -o pipefail

    local store=

    test "$1" = - && { store=1; shift;}

    # Was run without initial ".", or with insufficient parameters

        return 2

    test -n "$desc" || desc="the $1 password"

    function trace() { for arg in "$@"; do printf "%q " "$arg"; done; echo;}

    function traceSelf() { trace . "$self" - "$@";}

    if test -n "$store" -o -z "${!1+t}"; then # env var with name $1 is unset

        if test -n "$store"; then

            echo " To change the saved value for $desc, run: " >&2

            traceSelf "$@" >&2

        else

            test -t 2 && ccTty= || ccTty=1 # cc the tty if stderr is a log file

            {

                echo " You must first store $desc. \

At the shell, run: "

                traceSelf "$@"

            }|tee ${ccTty:+/dev/tty} >&2

        fi

        test -z "$store" && return 1 # just direct user how to store password

        read -s -p "Enter $desc: "; echo

        export "$1"="$REPLY"

    fi

}

env_password_main "$@"