Prunes Squiz CMS backups to the last X number of days. Will bail out if the backups have broken, to avoid deleting backups if they may be needed.

reduce-backups.sh

#!/bin/bash
#
# Reduces the total number of Squiz CMS backups to the last X days', whilst
# also ensuring at least X number of backups always exist.
#
# In other words, we want only the last X number of days' backups unless the
# backups have failed, in which case we'd prefer to keep the old ones until
# the backup is running again.
#
# dsimmons@squiz.co.uk
# 2012-01-20
#

filemask="???_????-??-??_??-??.tar.gz"

if [ $# -lt 2 ]; then
	echo "Reduces Squiz CMS backup files to the last X days'" >&2
	echo "Usage: $0 <path to backups> <number of last days' backups to keep> [-f]" >&2
	echo "  (-f means: actually do something - otherwise, just a dry-run)" >&2
	exit 99
fi

dir=$1
x=$2
[ "$3" != "-f" ] && dryrun=1

# Count total number of backup files
n=$(find "$dir" -mindepth 1 -maxdepth 1 -type f -name "$filemask" -print |wc -l)
[ $dryrun ] && echo "$n backups in total"

# Count number of backup files to be deleted
c=$(find "$dir" -mindepth 1 -maxdepth 1 -type f -name "$filemask" -daystart -mtime +$((x-1)) |wc -l)

if [ $c -eq 0 ]; then
	echo "No backups to delete."
	exit
elif [ $dryrun ]; then
	echo "$c to delete:"
	find "$dir" -mindepth 1 -maxdepth 1 -type f -name "$filemask" -daystart -mtime +$((x-1))
	echo "(Use -f to actually delete them)"
	exit
fi

# If the total number of backups *AFTER* deletion is less than the number of
# last days' backups we want to keep, then don't delete anything
if [ ! $(($n-$c)) -lt $x ]; then

	# Delete the backups
	find "$dir" -mindepth 1 -maxdepth 1 -type f -name "$filemask" -daystart -mtime +$((x-1)) -delete

else
	echo "WARNING: Skipping removal of backups as it would result in total number of backups less than. $x" >&2
	echo "HINT: Did your backup run yesterday?" >&2
fi