def find_job(tab, time=None, command=None, comment=None):
    """
    Finds the all jobs in the crontab that conforms to the specified parameters.

    :param tab:     Crontab to search in
    :param time:    Time filter
    :param command: Command filter
    :param comment: Comment filter
    :return:        All jobs that match the parameters
    """
    jobs = list()
    for job in tab:
        if time is not None and job != time:
            continue
        if command is not None and job.command != command:
            continue
        if comment is not None and job.comment != comment:
            continue
        jobs.append(job)
    return jobs