serverlog ownership

Hi,

I want to cat /dev/null > serverlog every night (after the backup is  
done) so that this file keep a small size.  Now, this file is owned  
by "root" and the backup is done by the user "postgres".  I want to  
change the permissions so that :

	-rw-r--r--  1 root     root      43M Jun 18 09:16 serverlog

become :

	-rw-rw-r--  1 root     postgres      43M Jun 18 09:16 serverlog

Does postmaster will complain about the new permissions or it's ok to  
do that ?