#!/bin/sh
#
# Forward mail if "fwd:<address>" is found in the subject of a message
#

SENDMAIL=/usr/sbin/sendmail
: ${TMPDIR:=/tmp}

hdr=$(mktemp $TMPDIR/fwmail.XXXXXX) || exit 1
body=$(mktemp $TMPDIR/fwmail.XXXXXX) || exit 1
awk -v hdr=$hdr -v body=$body '
/^$/ { hdr_done = 1 }
{ if (hdr_done) print >body; else print >hdr }'
addr=$(sed -n 's/^Subject: .* fwd:\([^ ]\{1,\}\).*$/\1/p' $hdr)
if [ -n "$addr" ]; then
    (
    sed -e 's/^\(To: \).*$/\1'$addr'/' -e 's/^\(Subject: .*\) fwd:.*$/\1/' $hdr
    cat $body
    ) | $SENDMAIL $addr
fi
rm -f $hdr $body
.