mail

#!/bin/bash
set -e

usage() {
	bin=$(basename $0)
	echo >&2 "Usage: $(basename "$0") [opts] rcpt [rcpt ...] < message"
	echo >&2 " opts: [-s subject] [-a 'header: value' [-a ...]] [-f mail-from@host]"
	echo >&2
	echo >&2 "Generated message headers:"
	echo >&2 "  $header_from"
	echo >&2 "  $header_date"
	echo >&2 "  Subject: [exactly as per -s option]"
	echo >&2 "  [any headers exactly as per -a values]"
	echo >&2 "  To: [all rcpt args, comma/space-separated]"
	echo >&2
	echo >&2 "Replacement for crappy sendmail wrappers that do"
	echo >&2 " too much stuff but can't/won't allow adding any random headers."
	exit ${1:-0}
}

user=$(id -un)
header_from="From: ${user} (${user})"
header_date="Date: $(date --rfc-822)"
letter=( "$header_from" "$header_date" )
rcpt=()
from=()
opt_chk=true

while [[ -n "$1" ]]; do
	case "$1" in
		-s) shift; letter+=( "Subject: $1" ); shift ;;
		-a) shift; letter+=( "$1" ); shift ;;
		-f) shift; from=( -f "$1" ); shift ;;
		--) opt_chk=; shift ;;
		-h|--help) usage ;;
		-*) [[ -z "$opt_chk" ]] || { echo >&2 "ERROR: unknown option - $1"; exit 1; } ;;
		*) rcpt+=( "$1" ); shift ;;
	esac
done

ifs_=$IFS; IFS=", "
letter+=( "To: ${rcpt[*]}" )
IFS=$ifs_; unset ifs_

[[ ${#rcpt[@]} -gt 0 ]] || usage 1

sendmail=/usr/bin/sendmail
[[ -e "$sendmail" ]] || sendmail=/usr/sbin/sendmail
[[ -e "$sendmail" ]] || { echo >&2 "ERROR: sendmail binary not found in /usr/{s,}bin"; exit 1; }
{ for line in "${letter[@]}"; do echo "${line}"; done; echo; cat; } |
	exec "$sendmail" "${from[@]}" "${rcpt[@]}"