Parsing mailq format (from Postfix 2.x)

mailq.py

#!/usr/bin/env python3
import subprocess
import re

from pypred import Predicate


SPACE = re.compile(r"\s+")

def mailq():
	mq = subprocess.Popen(['mailq'], stdout=subprocess.PIPE)
	buffer = []
	prems = True
	for line in mq.stdout:
		if prems:
			prems = False
			continue
		buffer.append(line[:-1])
		if line == b'\n':
			# Each entry shows the queue file ID, message size, arrival time, sender, and the recipients that still need to be delivered.
			meta = SPACE.split(buffer[0].decode("utf8"))
			id = meta[0]
			size = int(meta[1])
			sender = meta[-1]
			date = " ".join(meta[2:-1])
			dest = buffer[2].decode('utf8').strip()
			# FIXME sometime, there is more than one dest
			yield id, size, date, sender, buffer[1].decode('utf8'), dest
			buffer = []


def main():
	import sys
	if len(sys.argv) == 2:
		p = Predicate(sys.argv[1])
		if not p.is_valid():
			for error in p.errors()['errors']:
				print(error)
			return
	else:
		p = None
	for  id, size, date, sender, msg, dest in mailq():
		doc = dict(id=id, size=size, date=date, sender=sender, msg=msg, dest=dest)
		if p == None or p.evaluate(doc):
			print(doc)

if __name__ == '__main__':
	main()