Reading syslog output on a Mac

Question

/var/log/system.log

You can monitor it easily using tail -f /var/log/system.log

See also the "logger" (man logger) and "syslog" (man syslog).

You should probably use the Console.app to view logfiles. It's purdy.

Select your device on the left and filter messages on the right:

When in doubt, there's always man syslog.

You can find your messages in /var/log/syslog; my machine is set up out of the box to only include high level messages so you may need to have your settings.

You can also read the messages through syslog(1), or create a test message with a command like

$ syslog -s -l INFO "Hello, world."

use a severity of P ("panic") and you'll get an exciting message on your console immediately.

Maybe interesting to note: Apple was using a real syslogd in the past but meanwhile all of this has switched to ASL (Apple System Log). The syslog command is still available, but it will only access this one log. If you want to access all log messages of ASL across all log files configured, use the log command.

E.g. the following shows all log messages produced by Safari within the last two days (be patient, can take a while):

log show --predicate 'process == "Safari"' --last 2d

See man log for all the actions you can perform, all the parameters it knows and what attributes you can filter for.