To rotate your nginx log files, you can use the log file handler provided by FreeBSD: newsyslog.

Configuring /etc/newsyslog.conf

/var/log/nginx-access.log               644  7     1024 *     JC /var/run/nginx.pid
/var/log/nginx-error.log                644  7     1024 *     JC /var/run/nginx.pid

Before log rotation:

-rw-r--r--  1 root  wheel    104278002 Jul 16 11:35 nginx-access.log
-rw-r--r--  1 root  wheel      1509531 Jul 16 11:17 nginx-error.log

After log rotation:

-rw-r--r--  1 root  wheel        967 Jul 16 12:42 nginx-access.log
-rw-r--r--  1 root  wheel    5310443 Jul 16 12:41 nginx-access.log.0.bz2
-rw-r--r--  1 root  wheel         77 Jul 16 12:41 nginx-error.log
-rw-r--r--  1 root  wheel      37552 Jul 16 12:41 nginx-error.log.0.bz2

Links

• newsyslog man page
• newsyslog.conf man page