Purge backups with this simple script.

purge_backups.py

#!/usr/bin/env python
# author:   Daniel van der Meulen
# email:
# purpose:  Delete older backup files from directory
#           We keep files younger than 1 month AND
#           from the first day of the month from this year AND
#           from the first day of the year
#           Files that should not be deleted can be put in the exempt list
# curl -L https://gist.github.com/daniel70/6269559/download | tar xz --strip-components=1

import sys, os, time
from datetime import date

exempt = ['create_backup.sh']

now = time.time()
month_ago = now - 30 * 24 * 60 * 60
year_ago = now - 365 * 24 * 60 * 60


def keep(ts):
    # keep if younger than one month
    if ts > month_ago:
        return True

    d = date.fromtimestamp(ts)
    # keep if jan 1st
    if d.day == 1 and d.month == 1:
        return True

    # keep if 1st of month and less than 1 year old
    if d.day == 1 and ts > year_ago:
        return True

    return False


def purge(folder):
    this_file = sys.argv[0]

    for f in [os.path.join(folder, f) for f in os.listdir(folder) if os.path.isfile(os.path.join(folder, f))]:
        # don't delete myself
        if os.path.basename(this_file) == os.path.basename(f):
            print("sanctuary: %s" % f)
            continue

        if os.path.basename(f) in exempt:
            print("exempt: %s" % f)
            continue

        if not keep(os.path.getmtime(f)):
            os.remove(f)
            print("removing: %s" % f)
        else:
            print("keeping: %s" % f)


if __name__ == '__main__':
    # make sure a valid path was given
    if len(sys.argv) < 2:
        sys.exit('Usage: %s <dirname>' % os.path.basename(sys.argv[0]))

    if not os.path.isdir(sys.argv[1]):
        sys.exit('Error: directory %s does not exist!' % sys.argv[1])

    purge(sys.argv[1])