Python script to create desktop notifications for new mail that can be used by procmail

dbus_mail_notify.py

#!/usr/bin/python
# simple procmail filter to display a desktop notification
# usage: mailnotify username. Excepts the mail on stdin
# this is meant to live in a procmail recipe, for example:
# pipe the msg to this script to send a notification and deliver via
# dovecot-lda

#:0
#{
#    :0c
#    |/home/foobar/.local/bin/mailnotify.py foobar
#    :0:
#    |/usr/libexec/dovecot/dovecot-lda
#}

import sys
import os
import email
from email.parser import HeaderParser
from email.header import decode_header
import dbus
from pwd import getpwnam

nargs = len(sys.argv)

# you can customize this to set a different icon
desktop_entry = "thunderbird"

# missing user name argument -> exit
if nargs < 2:
    sys.exit(0)

euid = getpwnam(sys.argv[1]).pw_uid

# no stdin input -> exit

if os.isatty(sys.stdin.fileno()):
    sys.exit(0)

the_mail = sys.stdin

# performance: only parse headers, we do not need the body
parser = HeaderParser()
msg = parser.parse(the_mail)

# msg = email.parser.Parser().parse(the_mail)

# we need sender and the subject, not more
if "from" in msg and "subject" in msg:
    decoded_subject, charset = decode_header(msg["subject"])[0]
    decoded_from, charset = decode_header(msg["from"])[0]
    os.seteuid(euid)        # because procmail invoked by sendmail may run
                            # as root
    item = "org.freedesktop.Notifications"

    # notfy_intf = dbus.Interface(dbus.SessionBus().get_object(item, "/"+item.replace(".", "/")), item)

    # since procmail may run as root, we need to connect to the user's session bus
    # using the dbus socket. Using the dbus.SessionBus() won't work because it would
    # try to find root's session bus (which does not exist)
    # the desired user must be passed to this script as user name.
    bus_socket = "unix:path=/run/user/%s/bus" % euid
    # try to connect to the bus. if it fails, just bail out.
    try:
        notfy_intf = dbus.Interface(dbus.bus.BusConnection(bus_socket).get_object(item, "/"+item.replace(".", "/")), item)
        notfy_intf.Notify("New e-Mail message", 0, "emblem-mail",
                          decoded_subject, decoded_from, [],
                          {"urgency": 1, "action-icons": True, "desktop-entry": desktop_entry}, 5000)
        notfy_intf.close();
        # print(msg)
    except dbus.exceptions.DBusException:
        sys.exit(0)

sys.exit(0)