[Python-Dev] Help with inotify (original) (raw)

Neal Becker ndbecker2 at gmail.com
Fri Oct 28 02:33:12 CEST 2005

Bob Ippolito wrote:

On Oct 27, 2005, at 4:58 PM, Neal Becker wrote:

Bob Ippolito wrote:

On Oct 27, 2005, at 4:32 PM, Neal Becker wrote: "Martin v. Löwis" wrote:

I see. Python is making up the EISDIR, looking at the stat result. In Objects/fileobject.c:dircheck generates the EISDIR error, which apparently comes from posixfdopen, PyFileFromFile, fillfilefields. Python simply does not support file objects which stat(2) as directories.

OK, does python have a C API that would allow me to create a python file object from my C (C++) code? Then instead of using python's fdopen I could just do it myself. Why do you need a file object for something that is not a file anyway? select.select doesn't require file objects for example, just objects that have a fileno() method. Yes, that's a good point - the reason is I didn't want to restrict the interface to only work with select. Maybe I should rethink the interface. Well what would the interface do if you had a file object? Are you supposed to be able to read/write/seek/tell/etc.? I don't understand why you're trying to do what you're doing. select.select was just an example, select.poll's register/unregister takes any object with a fileno also.

Yes, you are supposed to be able to read and get information. However, I have implemented fileno for it, so you can use select.select on it if you just want to wait for something to happen - which is probably all that's really needed. I also implemented select as a method of my inotify object, in case you prefer that.

Here's an excerpt from documentation/filesystems/inotify.txt:

Events are provided in the form of an inotify_event structure that is read(2) from a given inotify instance. The filename is of dynamic length and follows the struct. It is of size len. The filename is padded with null bytes to ensure proper alignment. This padding is reflected in len.

You can slurp multiple events by passing a large buffer, for example

    size_t len = read (fd, buf, BUF_LEN);

Where "buf" is a pointer to an array of "inotify_event" structures at least BUF_LEN bytes in size. The above example will return as many events as are available and fit in BUF_LEN.

Each inotify instance fd is also select()- and poll()-able.

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