#!/bin/bash

FROM=''
TO=''
SUBJECT=''
MSG=''
AT='now'

usage() {
echo "
Usage: $0 OPTIONS [-w \"10:45AM 03/14/2042\"]
    -f From Address
    -t To Address
    -s Subject
    -m Message
    -w When to send (optional) @see 'man at'
"
}

while getopts ':f:t:s:m:w:h' flag; do
  case "${flag}" in
    f) FROM="${OPTARG}" ;;
    t) TO="${OPTARG}" ;;
    s) SUBJECT="${OPTARG}" ;;
    m) MSG="${OPTARG}" ;;
    w) AT="${OPTARG}" ;;
    h) usage; exit;;
    \?) echo -e "\nUnknown option: -$OPTARG" >&2;usage; exit 1;;
    :) echo -e "\nMissing argument for option -$OPTARG" >&2;usage; exit 1;;
  esac
done

if [ ! "$FROM" ] || [ ! "$TO" ] || [ ! "$SUBJECT" ] || [ ! "$MSG" ]
then
    usage
    exit 1
fi

echo "/usr/bin/mail -t <<EMAILMSG
To: $TO
From: $FROM
Subject: $SUBJECT
Content-Transfer-Encoding: 8bit
Content-Type: text/plain; charset=UTF-8

$MSG
EMAILMSG
" | at ${AT}