Plesk wp-cron staggered scheduler

plesk-staggered-cron.sh

#!/usr/bin/env bash
#####################
# Buggy, but good enough.
# Walks over users' Plesk-managed wp-cron entries, to change this:
#   <whatever> * * * * /opt/plesk/php/8.2/bin/php -f 'httpdocs/wp-cron.php'
# ...into something like this:
#   7,23,39,55 /opt/plesk/php/8.2/bin/php -f 'httpdocs/wp-cron.php'
# so that wp-cron runs are spread out as much as possible,
# to reduce simultaneous memory usage.
#####################
i=1

WEBUSERS="$(grep -lE '^[^#].*plesk.*wp-cron.php' /var/spool/cron/* | cut -d/ -f5)"
NUSERS="$(echo "$WEBUSERS" | wc -l)"

echo "Dividing wp-cron jobs into a staggered schedule..."

for WEBUSER in $WEBUSERS; do
	MINS=
	for j in {0..59}; do
		if [ $((j % NUSERS)) == $((i % 60 % NUSERS)) ]; then
			MINS="$MINS $j"
		fi
	done
	NEWSCHED="$(echo $MINS | tr ' ' ',') * * * *"
	
	echo -ne "$WEBUSER:\t"
	
	( crontab -l -u "$WEBUSER" \
		| perl -pe 's/^(?<!#)(?:[\w*][ \t]+){5}(.+plesk.+wp-cron.php.+)$/'"$NEWSCHED"' $1/' \
		| tee /proc/self/fd/3 \
		| crontab -u "$WEBUSER" - ;
	) 3>&1 | grep wp-cron

	i=$((i+1))
done