UNIX for Dummies Questions & Answers

avahi error message goes to /var/log/messages , how can put avahi to log the error in a file /var/log/avahi-error instead of /var/log/messages

If it's currently logging to /var/log/messages, it's probably doing so using the syslog daemon.
Find the section in your log that says something like "[ID 123456 daemon.notice]". This is the log facility and level that your app is logging as.

Then just create a new entry in /etc/syslog.conf for this pointing to your new log file location, create a blank file in the log location, and send a SIGHUP to syslogd.