Calculate time of crons

crons_list.py

from __future__ import print_function
import sys
# import debugpy
from dateutil import rrule
from datetime import datetime, timezone, timedelta
from croniter import croniter
from collections import defaultdict

def main(crontab, start, end, fromDuration):
    """
    Take entries in a crontab file, find slots where no jobs are scheduled to
    run.
    1. Install dependencies:
    - Python 3
    - Python package manager https://pip.pypa.io/en/stable/installing/
    2. Install additional modules:
    - pip3 install python-dateutil
    - pip3 install croniter
    3. How to run:
    python cron_slots.py <crontabfile> <start time dd/mm/yyyy h24:mi> <end time dd/mm/yyyy h24:mi> <from duration in minutes>
    crontab -l > crontab_01012016
    python cron_slots.py "path/to/crontab_01012016" "19/08/2022 00:00" "02/09/2022 23:59" "1"
    Parameters
    ----------
    crontab: A file with output of crontab -l command.
    start: start of time period, datetime.
    end: end of time period, datetime.
    fromDuration: find of time period from the duration in minutes.
    returns
    -------
    None, output is printed out to standard out in below format
    04/02/2016 00:00 - Free 1 min
    04/02/2016 00:01 - Busy with /cfes/bin/script1.sh # Note this is the first script running at 00:01
    04/02/2016 00:01 - Busy with /cfes/bin/script2.sh # Note this is the second script running at 00:01
    04/02/2016 00:10 - Free 9 min
    04/02/2016 00:11 - Busy with /cfes/bin/script3.sh # Note this is the thirst script running at 00:01
    """

    cron_times = defaultdict(list)
    f = open(crontab, 'rt')

    print('IGNORED LIST START -------------------')
    for line in f:
        try:
            line_split = line.split()

            # take the cron time part, e.g 10 * * * *
            cron_entry = ' '.join(line_split[:5])

            cron_times_iter = croniter(cron_entry, start)
        except Exception as _:
            if line != '\n':
                print(line)
            continue

        for epoch in cron_times_iter:
            dt = datetime.fromtimestamp(epoch, timezone.utc)
            if dt > end:
                break
            cron_task = ' '.join(line_split[5:])
            cron_times[dt.strftime('%d%m%Y%H%M')].append(cron_task)

    print('IGNORED LIST END -------------------')

    print('FREE TIME START -------------------')

    duration = 0
    lastCronDate = None
    dates = rrule.rrule(rrule.MINUTELY, dtstart=start, until=end)

    for dt in dates:
        if dt.strftime('%d%m%Y%H%M') in cron_times:
            isPrintable = duration > fromDuration
            

            if isPrintable and lastCronDate is not None:
                print('-------------------')
                for task in cron_times.get(lastCronDate.strftime('%d%m%Y%H%M'), {}):
                    print(lastCronDate.strftime('%d/%m/%Y %H:%M'), '- Busy with ',
                        task)

            if isPrintable:
                print((dt - timedelta(minutes=1)).strftime('%d/%m/%Y %H:%M'), '- Free ',
                    duration, 'min')
                print('-------------------')
            
            duration = 0
            lastCronDate = dt
        else:
            duration += 1

    isPrintable = duration > fromDuration
    if isPrintable and lastCronDate is not None:
        print('-------------------')
        for task in cron_times.get(lastCronDate.strftime('%d%m%Y%H%M'), {}):
            print(lastCronDate.strftime('%d/%m/%Y %H:%M'), '- Busy with ',
                task)

    if isPrintable:
        print(end.strftime('%d/%m/%Y %H:%M'), '- Free ',    
            duration, 'min')

    print('FREE TIME END -------------------')

if __name__ == '__main__':
    # debugpy.listen(5678)
    # print("Waiting for debugger attach")
    # debugpy.wait_for_client()
    # debugpy.breakpoint()

    cronfile = sys.argv[1]
    start = datetime.strptime(sys.argv[2], '%d/%m/%Y %H:%M').replace(tzinfo=timezone.utc)
    end = datetime.strptime(sys.argv[3], '%d/%m/%Y %H:%M').replace(tzinfo=timezone.utc)
    fromDuration = int(sys.argv[4])

    main(cronfile, start, end, fromDuration)