The Selectors function are encoded as a facility a period (``.''), and a level with no intervening white-space. Both the facility and the level are case insensitive.
The facility describes the part of the system generating the message, and is one of the following keywords: auth, authpriv, cron, daemon, kern, lpr, mail, mark, news, syslog, user, uucp and local0 through local7. These keywords (with the exception of mark) correspond to the similar ``LOG_ '' values specified to the openlog(3) and syslog(3) library routines.
The level describes the severity of the message, and is a keyword from the following ordered list (higher to lower): emerg, alert, crit, err, warning, notice and debug. These keywords correspond to the similar (LOG_ ) values specified to the syslog library routine.
See syslog(3) for a further descriptions of both the facility and level keywords and their significance.
If a received message matches the specified facility and is of the specified level (or a higher level) the action specified in the action field will be taken.
Multiple selectors may be specified for a single action by separating them with semicolon (``;'') characters. It is important to note, however, that each selector can modify the ones preceding it.
Multiple facilities may be specified for a single level by separating them with comma (``,'') characters.
An asterisk (``*'') can be used to specify all facilities or all levels
By default, a level applies to all messages with the same or higher level The equal (``='') character can be prepended to a level to restrict this line of the configuration file to messages with the very same level
An exclamation mark (``!'') prepended to a level or the asterisk means that this line of the configuration file does not apply to the specified level (and higher ones). In conjunction with the equal sign, you can exclude single levels as well.
The special facility ``mark'' receives a message at priority ``info'' every 20 minutes (see syslogd(8)). This is not enabled by a facility field containing an asterisk.
The special level ``none'' disables a particular facility
The action field of each line specifies the action to be taken when the selector field selects a message. There are five forms:
You may prepend a minus (``-'') to the path to omit syncing the file after each message log. This can cause data loss at system crashes, but increases performance for programs which use logging extensively.
Blank lines and lines whose first non-blank character is a hash (``#'') character are ignored.
A configuration file might appear as follows:
# Log all kernel messages, authentication messages of # level notice or higher and anything of level err or # higher to the console. # Don't log private authentication messages! *.err;kern.*;auth.notice;authpriv.none /dev/console # Log anything (except mail) of level info or higher. # Don't log private authentication messages! *.info;mail.none;authpriv.none /var/log/messages # The authpriv file has restricted access. authpriv.* /var/log/secure # Log all the mail messages in one place. mail.* /var/log/maillog # Everybody gets emergency messages, plus log them on another # machine. *.emerg * *.emerg @arpa.berkeley.edu # Root and Eric get alert and higher messages. *.alert root,eric # Save mail and news errors of level err and higher in a # special file. uucp,news.crit /var/log/spoolerr