#!/bin/bash

# Sets a password environment variable

self="$(readlink -f -- "$BASH_SOURCE")"

set -o pipefail

test "${BASH_LINENO[0]}" = 0 && missing_dot=true || missing_dot=false

    # whether run without initial "."

store=

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

if $missing_dot || ! test "$#" -ge 1; then

    $missing_dot && self="$0"

    echo "Usage: . $self env_var [desc] (note initial \".\")"|fold -s >&2

    exit 2

fi

desc="$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" && exit 1 # just direct user how to store password

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

    export "$1"="$REPLY"

fi