Mini Shell

# -*- coding: utf-8 -*-

# Copyright © Cloud Linux GmbH & Cloud Linux Software, Inc 2010-2019 All Rights Reserved
#
# Licensed under CLOUD LINUX LICENSE AGREEMENT
# http://cloudlinux.com/docs/LICENSE.TXT

from __future__ import print_function
from __future__ import division
from __future__ import absolute_import
import os
import sys
import random

__ALL__ = ["add_cron", "erase_cron", "remove_cron", "add_cron_task"]


def add_cron(file_name, minute, hour, day, month, day_of_week, user, command,
             check_command=True):
    """
    Add new cron task into crontab schedule iff this task or command wasn't already existed in the cron-file.

    :param str file_name: Name of cron-file in /etc/cron.d
    :param minute: Integer or char 'r' if to set random minute
    :param hour: Integer or char 'r' if to set random hour
    :param int, str day: Day number
    :param int, str month: Month number
    :param int, str day_of_week: Day of week number
    :param str user: Under what user do run command
    :param str command: What command do run
    :param bool check_command: If it is False, check that whole cron-task line already exists in crontab,
        check that command string exists instead. Default is True, check a command string.
    """
    if minute == 'r':
        minute = int(round(random.uniform(0, 59)))  # pylint: disable=round-builtin
    if hour == 'r':
        hour = int(round(random.uniform(0, 23)))  # pylint: disable=round-builtin
    try:
        cron_task = format_cron_task(minute, hour, day, month, day_of_week, user, command)
    except TypeError:
        sys.stderr.write("Can not add task with wrong syntax")
    add_cron_task(file_name, cron_task, check_command)


def add_cron_task(file_name, task, check_command=False):
    """
    Add new cron task in cron format iff this task or command in this task wasn't already existed in the cron-file.

    :param str file_name: Name of cron-file in /etc/cron.d
    :param str task: Cron task in format "min hour day mon d_of_w user command"
    :param bool check_command: If it is False, check that whole cron-task line already exists in crontab,
        check that command string exists instead. Default is False, check a whole cron-task string.
    """
    f = None
    try:
        f = open('/etc/cron.d/' + file_name, 'a+')
        if not is_in_cron(task, f, check_command):
            f.write("%s\n" % task)
    except (IOError, OSError):
        if f is not None:
            f.close()
        return False
    f.close()
    return True


def remove_cron(file_name):
    """
    Remove cron-file from fs

    :param str file_name: Name of cron-file in /etc/cron.d
    """
    try:
        os.remove('/etc/cron.d/' + file_name)
    except (OSError, IOError):
        pass


def erase_cron(file_name):
    """
    Make cron-file empty

    :param str file_name: Name of cron-file in /etc/cron.d
    """
    f = None
    try:
        f = open("/etc/cron.d/" + file_name, "w")
    except (IOError, OSError) as err:
        sys.stderr.write("Can not erase crontab file %s because %s\n" % (
            file_name, str(err)))
    if f is not None:
        f.close()


def format_cron_task(minute, hour, day, month, day_of_week, user, command):
    """
    Build cron-task string in the cron format

    :param minute: Integer or char 'r' if to set random minute
    :param hour: Integer or char 'r' if to set random hour
    :param int day: Day number
    :param int month: Month number
    :param int day_of_week: Day of week number
    :param str user: Under what user do run command
    :param str command: What command do run
    :return: Cron-task in the cron format
    :rtype: str
    """
    arguments = (minute, hour, day, month, day_of_week, user, command)
    for arg in arguments:
        if arg is None:
            raise TypeError("Wrong schedule for cron task")
    return "%2s %2s %2s %2s %2s %10s %s" % arguments


def parse_cron_task(task):
    """
    Split cron task string into cron task parts

    :param str task: Cron-task string in the cron format
    :return: List of cron-task parts
    :rtype: list of str
    """
    return task.split(None, 6)


def get_task_in_cron(crontab, get_parsed=False):
    """
    Returns iterator through crontab tasks

    :param iterable crontab: Iterator with crontab tasks' strings
    :param bool get_parsed: If it is True, return crontab task as list of task's parts
        return crontab task as a string instead
    :return: Crontab task
    :rtype: str
    :rtype: list of str
    """
    for cron_t in (s.strip() for s in crontab):
        try:
            if get_parsed:
                t = parse_cron_task(cron_t)
            else:
                t = format_cron_task(*parse_cron_task(cron_t))
        except TypeError:
            sys.stderr.write("Wrong crontab task syntax: %s\n" % cron_t)
        else:
            yield t


def is_task_in_cron(task, fd):
    """
    Find first occurence of task in cron-file if it has

    :param str task: Cron-task in cront format to compare with
    :param file fd: File descriptor of opened cron file
    :return: True if such a task is already existed in cron-file, False instead
    :rtype: bool
    """
    for t in get_task_in_cron(fd.readlines()):
        if t == task:
            return True
    return False


def is_command_in_cron(task, fd):
    """
    :param str task: Task with command to looking for
    :param file fd: File descriptor of opened cron file
    :return: True if such a command is already existed in cron-file, False instead
    :rtype: bool

    Find first occurence of command in cron-file if it has
    """
    command = parse_cron_task(task)[-1]
    for t in get_task_in_cron(fd.readlines(), get_parsed=True):
        if t[-1] == command:
            return True
    return False


def is_in_cron(task, fd, check_command=False):
    """
    Find first occurence of command or task in cron-file if it has

    :param str task: Task or command to looking for
    :param file, BinaryIO fd: File descriptor of opened cron file
    :param bool check_command: If it is True, check command occurence, check task occurence instead
    :return: True if such a command or task is already existed in cron-file, False instead
    :rtype: bool
    """
    if check_command:
        return is_command_in_cron(task, fd)
    return is_task_in_cron(task, fd)