Mac® Security Bible

19.4. Understanding the Console and System Logs

In addition to all the application- and process-specific log files Mac OS X stores, there are two special (and especially important) logs that don't fit the mold of the others: the console log and the system log.

The word console has several different meanings when applied to computers. Sometimes, for example, it refers to a terminal emulator program, but sometimes, it refers more generally to a command-line environment. These meanings, in turn, are metaphorical extensions of an earlier sense of console as a physical device (a keyboard paired with a display or printer) one used to interact with a multi-user computer system. In any case, whether you're talking about an old-fashioned mainframe or Mac OS X's command-line interface, the notion of sending output to the console refers to a program delivering some sort of textual message to whatever it considers the default location, where the operator can see it and take whatever action is required.

The Unix processes and GUI programs that make up Mac OS X send messages to the console constantly, but unless you're using Terminal to run a command-line program interactively, you normally never see these messages. In Mac OS X, they go into a special database called asl.db, whose contents can be displayed in real time by a utility included with Mac OS X that's called — you guessed it — Console. I discuss Console just ahead. So, one use of the Console utility is to display console messages. ...