About
frotate stands for "functional rotate", whatever.
This is an evolution of the log2rotate's ideas.
See also pylog2rotate.
frotate is designed to rotate backups with any balance between retention
and space usage. Instead of rotating backups using some familiar method such
as daily, weekly, monthly, and yearly periods, it rotates backups using any
periods. Thus "functional".
The idea is simple, the rotation schedule is determined by an integer function.
This function gives us a period (number) of days when we must encounter at
least one backup or whatever we are rotating. When we use an exponential
function, the scheme is similar to the radioactive decay law. When the
funtion is simply a constant 1, we don't rotate anything and retain all
the backups. If it is 2, we retain each second backup. With some trivial
function we can achieve a well-known dayly-weekly-monthly-yearly scheme.
The frotate command line utility implements only exponential periods with
arbitrary base (ensure it is > 1, or have fun otherwise).
Usage
Note that when neither --keep nor --delete option is given, the utility
prints all intervals with all days in them to standard error. In production
you will need to specify --keep or --delete explicitly.
Usage: frotate ([-k|--keep] | [-d|--delete]) [-b|--base BASE] DAY...
Available options:
-k,--keep Print days to keep
-d,--delete Print days to delete
-b,--base BASE Base of the exponent (default: 1.1)
-h,--help Show this help text
Example
Different modes with the same days:
$ frotate --base 2 2019-08-31 2019-08-30 2019-08-29 2019-08-28 2019-08-27 2019-08-26 2019-08-25 2019-08-24
2019-08-31
2019-08-29 2019-08-30
2019-08-25 2019-08-26 2019-08-27 2019-08-28
2019-08-24
$ frotate --keep --base 2 2019-08-31 2019-08-30 2019-08-29 2019-08-28 2019-08-27 2019-08-26 2019-08-25 2019-08-24
2019-08-31 2019-08-29 2019-08-25 2019-08-24
$ frotate --delete --base 2 2019-08-31 2019-08-30 2019-08-29 2019-08-28 2019-08-27 2019-08-26 2019-08-25 2019-08-24
2019-08-30 2019-08-26 2019-08-27 2019-08-28
More or less realistic example when we keep some backups and get new ones, but not every day:
$ frotate --keep --base 2 2019-09-01 2019-08-31 2019-08-30 2019-08-28 2019-08-24
2019-09-01 2019-08-30 2019-08-28 2019-08-24
$ frotate --keep --base 2 2019-09-05 2019-09-01 2019-08-30 2019-08-28 2019-08-24
2019-09-05 2019-08-30 2019-08-24
$ frotate --keep --base 2 2019-09-06 2019-09-05 2019-08-30 2019-08-24
2019-09-06 2019-09-05 2019-08-24
$ frotate --keep --base 2 2019-09-07 2019-09-06 2019-09-05 2019-08-24
2019-09-07 2019-09-05 2019-08-24
$ frotate --keep --base 2 2019-09-08 2019-09-07 2019-09-06 2019-08-24
2019-09-08 2019-09-06 2019-08-24
$ frotate --keep --base 2 2019-09-09 2019-09-08 2019-09-06 2019-08-24
2019-09-09 2019-09-08 2019-09-06 2019-08-24
