Watching files

[neko-kai]

The library is marketed as "Cross platform library for file creation, modification, and deletion notification", yet there is no function to watch a single file.

[gregwebs]

the latest code on github has already been modified to support deletion but needs to be tested out

[mdittmer]

Is the issue support for deletion, or support for watching a particular file name rather than files in a particular directory (optionally: and its subdirectories)?

[neko-kai]

@mdittmer
Second.

[nh2]

Yes, watching single files would be very useful.

Do the underlying OS APIs allow this on non-Linux platforms?

[gregwebs]

I think FSEvents only watches directories, but @feuerbach was looking at adding a kqueue backend.

[UnkindPartition]

@nh2 an important question to answer is whether you want to watch a path or an inode.

Some OSes allow watching inodes, but I don't know any that allow watching paths. And watching paths is most probably what you need.

I outlined a way to watch paths in #41.

[nh2]

@feuerbach I use it to watch my own executable in my selfrestart package and restart it when it changes (https://github.com/nh2/selfrestart/blob/94cb8e75f4ccbfa993a4a56e15c08d10ce8b10c3/System/SelfRestart.hs#L47).

I guess whether I want to watch a file or an inode depends on how my change of executable is being written - if it's deleted and re-created, watching the inode will probably not work.

[UnkindPartition]

Exactly. Watching an inode is very fragile, and I have a hard time coming up with an example where one would prefer watching the inode to watching the path.

[mhitza]

I would like to have this feature in as well, that way I could use hfsnotify in a cross OS way instead of relying on hinotify

[LeifW]

Currently I'm thinking of doing this just by making the predicate check the filename. Sometimes things get into trouble when it watches more than it should, e.g. broken symlinks some apps create in /tmp.