Had a sysinternals tool (filemon) for that, but now I can find something similar for the mac.

I'm a developer and I basically want to debug "file not found" or "wrong permissions" errors.

4 Answers 4


You can use lsof or fs_usage in Terminal. lsof can be quite powerful. If it's about a specific process, you can try sampling it in Activity Monitor.

For a GUI tool, my recommendation is fseventer:

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More GUI-oriented utilities, which I haven't used:


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FS Spy

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  • +1 very nice answer. Btw, I've just tried FileMon and the filtering doesn't seem to work, which makes it pretty useless. fseventer is very nice.
    – occulus
    Feb 27, 2013 at 10:59
  • fseventer claims "10.10 Yosemite is classified as unsupported till further notice". is there an updated answer? are there new recommendations?
    – rafraf
    Jul 14, 2015 at 9:55

Less visual

https://diigo.com/0xcp0 for highlights from Brendan's blog » Top 10 DTrace scripts for Mac OS X (2011-10-10).

More visual

For more modern operating systems that are incompatible with fseventer, there's Apple Xcode Instruments –

selecting the File Activity template

Instruments in the background, Terminal in front

– powerful, but (compared to fseventer) in some cases, Instruments may be too heavyweight.


For viewing what files are accessed in real time you can leverage fs_usage part of the FSEvents feature in Mac OS X or even dtrace itself.

Usage: sudo fs_usage [PID].

For more info, check out the man page


You can use the dtrace opensnoop script to identify failed opens (file not found and permission errors)

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