Since there are comments below asking about benchmarks, others noting or expressing interest in other projects, I'll drop the one I made: https://github.com/e-dant/watcher
There are benchmarks in there, and comparisons with all the other watchers out there I could find at the time I made it (see "Comparison with Similar Projects" at the very bottom of the readme).
It's a pretty long list. Tons of watchers out there with different design philosophies and shapes of problems they solve.
Nice writeup. I work on native macOS utilities and have dealt with file monitoring quite a bit. kqueue is reliable but the per-file descriptor requirement can get tricky when you need to watch large directory trees.
For anyone looking at this space, FSEvents is the higher-level alternative Apple provides. It watches directory-level changes without needing a file descriptor per file, which scales better for broad monitoring. But kqueue gives you more granular control, like detecting attribute changes or renames specifically, which FSEvents sometimes lumps together.
In practice I've found a combination works well: FSEvents for broad directory watching to catch that something changed, then kqueue for targeted monitoring of specific files you care about.
Love it. Are there any benchmarks available on how fast this is from file change, kernel event received, event dispatched? I would expect it to be really quick.
There are benchmarks in there, and comparisons with all the other watchers out there I could find at the time I made it (see "Comparison with Similar Projects" at the very bottom of the readme).
It's a pretty long list. Tons of watchers out there with different design philosophies and shapes of problems they solve.
For anyone looking at this space, FSEvents is the higher-level alternative Apple provides. It watches directory-level changes without needing a file descriptor per file, which scales better for broad monitoring. But kqueue gives you more granular control, like detecting attribute changes or renames specifically, which FSEvents sometimes lumps together.
In practice I've found a combination works well: FSEvents for broad directory watching to catch that something changed, then kqueue for targeted monitoring of specific files you care about.
For more software in this domain see also the excellent entr https://eradman.com/entrproject/
The OpenBSD documentation for it is top notch, as usual. No idea about the rest (I suspect they’ve all converged at this point).