#! /bin/sh
set -euf

# require flock from util-linux
if test "${FLOCK-}" != "$state_file"; then
  exec env FLOCK="$state_file" flock "$state_file" "$0" "$@"
fi

to="$_from"

# print messages
sed -n '/^'"$to"' /{
  s/^\([^ ]\+\) \([^ ]\+\) <\([^>]\+\)> \(.*\)/\1: \4 2-- \2, \3/p
}' "$state_file"

# delete messages
sed -i '/^'"$to"' /{
  d
}' "$state_file"