t.py

import re
import os

fd = open('/etc/crontab')
ignored_lines = 0
shell = path = mailto = ''
crons = list()

shell_pattern = re.compile('SHELL=["\']?((/[a-zA-Z]+)+)["\']?')
path_pattern = re.compile('PATH=["\']?(((/[a-zA-Z]+)+:?)+)["\']?')
mailto_pattern = re.compile('MAILTO=([a-zA-Z0-9\-_]+(@[a-zA-Z0-9\-_]+\.[a-zA-Z0-9\-_]+)?)')
command_match = re.compile('#?(((((([0-9]+,?)+)|\*|(\*/[0-9]+)))[ \t]+){5}([a-zA-Z0-9]+)[ \t]+(.+))')
comment_match = re.compile('#.+')


class CronItem:
    pre_comment = cmd = moh = hod = dom = moy = dow = ''
    commented = False

    def __init__(self):
        pass

line = 0
for x in fd:
    line += 1
    if len(x.strip()) > 0:
        match = shell_pattern.match(x)
        if match and len(match.groups()) > 0:
            shell = match.groups()[0]
            continue

        match = path_pattern.match(x)
        if match and len(match.groups()) > 0:
            path = match.groups()[0]
            continue

        match = mailto_pattern.match(x)
        if match and len(match.groups()) > 0:
            mailto = match.groups()[0]
            continue

        match = command_match.match(x)
        if match and len(match.groups()) > 0:
            cmd = str(match.groups()[-1])
            print os.execl("/bin/bash", ' -n', cmd)
            continue

        match = comment_match.match(x)
        if match and len(match.groups()) > 0:
            match.groups()
            continue

        print(" line %s is not valid" % line)