monitor all changes to files on UNIX system

Question

I'm trying to figure out what changes to disk an app does.. and it's very messy. I'd like a way to monitor my entire file system for a few seconds to know which files have been accessed and written to. I thought of checking the modified date.. but of course it takes ages to do that for every file... there must be a cleverer way!

Answer 1

Check out fs_usage (shows all filesystem activity), creatbyproc.d (just file creation), filebyproc.d (just file opens), opensnoop (similar, different format), and rwsnoop (reads and writes).

Answer 2

For Linux, you'd check into 'inotify'. Quick research indicates the same tech for OSX is called 'kqueue'. It hooks into the filesystem and fires when events happen.

As usual, IBM has an excellent article.