Brian McNett Feb 4, 2000 Feb 4, 2000 10 perl daemon On the Mac, under MacPerl, one can't fork a process like Unix, and there's no "root" to place such a process to begin with. Nevertheless, Brian McNett was able to put together a Mac daemon equivalent with a little help from Chris Nandor. On the Mac, under MacPerl (as it's currently written), one can't fork a process, and there's no root to place such a process to begin with. Thus, unless you want to patch the operating system at startup, your process has to live in the application heap with all the other user processes. A true unix-like daemon is not an option (alas) in MacPerl. It is possible, however, to create a runtime application, which is basically a cut-down MacPerl app with just the interpreter and a copy of your code, (and sometimes even all the modules it uses as well, but that's an issue for another day) which it executes. The heavy lifting in the program is done by three modules: Mac::Processes, Mac::Apps::Launch, and Mac::Speech. Processes.pm and Speech.pm are interfaces to the Mac Toolbox APIs for the Process Manager and Speech manager. As such, the details involving their use are found in Apple's extensive technical tome Inside Macintosh. I've written a quick tutorial on using Mac::Speech, which appeared in issue #6 of PerlMonth. I recommend it, as it's a fun read. After loading in our modules, we immediately invoke Mac::Apps:Launch::Hide(), and tell it to force MacPerl into the background. Next, we create a new speech channel using Mac::Speech::NewSpeechChannel(). I'm not going into detail about what arguments NewSpeechChannel() takes, as I did that in my PerlMonth article. Still it should be clear that there is a hash Mac::Speech::%Voice, and I've passed a member of that hash $Voice{Victoria} to NewSpeechChannel(), and assigned the result to $channel. for (;;) { Next we loop forever, or at least until someone brings the application to the front and aborts it by typing Cmd-. (Cmd is that funky clover-leaf key, and Cmd-. is pretty much standard for aborting a running process). processSignature(), $psi->processName(), $psi->processSize() ); ]]> This program doesn't log its output to a file (I could have done that, though), but just prints it to the MacPerl console. Each iteration gets a timestamp. Then for each member of the hash %Process (which is a hash of hashes, containing the _processInfoMap for each currently running process), we extract the application signature which is a unique four character code used to identify each application: MACS for the Finder, R*ch for BBEdit, and so forth. We then do the same for the application name (which is just what it says it is). Finally, we get the application size in bytes. Once again, I'm not giving ALL the details (a reading of Inside Macintosh is REALLY required!). processName(); }]]> In the previous bit of code, printf() handled the appropriate coercion for us. It's implicit when we say printf("%s") that we want the output coerced to a string. In the next step, however, we have to do the coercion ourselves. SpeakText() expects a string as its argument, so we assign $psi->processName() to $process_name. Whenever you make a call to SpeakText(), it needs to be followed by a call to while( SpeechBusy()){}. You could actually do something inside that loop while waiting for the speech to end, but I've chosen not to (keeping things simple). sleep(15); Finally, we put the program to sleep for 15 seconds. During that time, MacPerl will indicate to the OS that it's not doing anything, and the OS will make that unused time available to the other processes. One last detail! If somehow, the code breaks out of its infinite loop (say someone does invoke Cmd-.), we need to dispose of the open speech channel. DisposeSpeechChannel($channel); Matthias Neeracher is busily re-writing MacPerl to take advantage of GUSI2. GUSI is Matthias' Generic Universal Socket Interface, essentially a network socket and POSIX library for the Mac. GUSI2 adds pthreads, and a host of other features which will allow Matthias to finally bring MacPerl into sync with the standard distribution. No word on how far he is from completion. Eventually, the Mac in MacPerl will devolve into an extended set of modules for the Mac Toolbox and Graphics APIs which will run directly over the standard Perl. The above code will likely survive that change, but it will then be possible to write a normal daemon process on the Mac. Brian McNett is Webmaster of Mycoinfo, the world's first mycology e-journal. He's also a regular contributor to Mother of Perl where he keeps things Mac friendly. Please send comments, praises, and sizable cash contributions to webmaster@mycoinfo.com The full source code to the MacPerl daemon is available at: http://www.motherofperl.com/tutorial/10/macdaemon.pl