Launchd WatchPath Arguments?

Question

Hi all,
I wish to create a small script that takes a file in a directory, gets its metadata (with 'mdls') and appends this to the end of a text file.
This is not a problem when 'batch' processing the contents of an entire directory. However, I wish to set the dir as a launchd 'watchpath' and have it call the script whenever a file is added. This has created several problems for which I cannot see a solution...
1) How can I identify which files have been added to the directory and pass these as arguments to the script? If that is not possible, can I identify them by some other methd?
2) As the script would be executed on ANY modification of the directory, how can I distinguish between the addition of files and the removal of files. As this is a log of all files that have passed through the dir, I don't wish to overwrite the txt file when something is removed.
Should I forget using launchd and use folder actions? Off the top of my head, I think an applescript would do the trick.
Cheers for any help
G4 450 Sawtooth   Mac OS X (10.4)   720Mb ram

Answer 1

Hi Rob,
   I can't help you decide between Folder Actions and WatchPaths except to suggest that it boils down to whether you are more comfortable with shell scripts or AppleScripts. I hope that it doesn't surprise you that on this forum you're going to hear a number of votes for shell scripts and that's certainly the way I lean. I'm far better at shell scripts than AppleScripts and I would say that it's because of the difference in the quality of the documentation.
   I use something in the rough direction of what you describe. I call it newlog and it's just a three line script:
date
diff ~luminis/.new_logs.txt <( find $CP_ROOT -name ".log" -ls )
find $CP_ROOT -name ".log" -ls >| ~luminis/.new_logs.txt
The output isn't pretty but it tells me every log file that has changed since the last time the script was run. It does this by searching for the log files and dumping the output into a file. The output is a long listing of the file. The next time it runs it performs the search again and uses the "diff" command to compare the latest search with the previous "dumped" one. Then it runs the search another time, again dumping the output into the file to "freshen" it. The part of the listing that changes will of course be the modification date. That way I can get a report of which log files have changed.
   You can do something similar but you probably don't need the "find" command. You can just do a listing of everything and save it. Then each time the script is run, it compares a new listing with the saved one. If you use the "diff" command to do that, its output will contain arrows ('<'re really doing is keeping a text copy of records that are already kept elsewhere in the system. For what do you need this?
   Anyway, if you need help with this script, provide some details and I'll help you write it. I've done stuff like this before. In fact, I have a script that compares directories with what the contents should be as predicted by the BOM files in the installer package receipts.
Gary
~~~~
   If you couldn't find any weirdness,
   maybe we'll just have to make some!
      -- Calvin