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pnotify
pnotify is an event notification framework for monitoring files and
directories. It is designed to be portable across different Unix-like
operating systems, and currently supports Linux and BSD. The
[1]pnotify API is very similar to the [2]inotify API under Linux.
___________________________________
[3]Download | [4]Documentation | [5]Mailing list
___________________________________
Rationale
Kernel-based filesystem event notification is a relatively new
phenonemon, and several different approaches have been taken by
various operating systems. Linux uses inotify, BSD uses kqueue, Apple
has kqueue and it's own Spotlight system calls, Solaris has FEM,
Windows has the NTFS Change Journal and the ReadDirectoryChangesW
function, and so forth.
The goal of pnotify is to provide a simple, cross-platform API for
monitoring filesystem events. The library will conceal all of the
messy implementation-specific details from the user and help them to
write more portable programs.
History
pnotify was born out of an effort to port the inotify API from Linux
to BSD. This initial effort took the form of a userspace library that
would translate inotify requests into their kqueue(4) equivalent.
After some time, it became clear that kqueue was not sophisticated
enough to support all of the functionality of inotify. There was also
the problem of threadsafety; inotify relies on shared global data
structures, which is normal within the kernel but complicates the
design of a userspace library.
Eventually, it became clear that a new API was needed to address these
portability and threadsafety issues. This new API became 'pnotify', to
indicate that it is a portable subset of the inotify API.
Supported Platforms
pnotify has been ported to the following platforms:
* Linux 2.6
* OpenBSD 4.0
* NetBSD 3.0
* MacOS/X 10.4
There are platforms that are not supported due to lack of developer
resources. Interested parties with access to these platforms are
encouraged to port the library to their platform. For example:
* Sun OpenSolaris will soon get a similar API called FEM that could
be supported.
* Microsoft Windows has a filesystem event notification mechanism
At the current time, there is no generic polling mechanism to use as a
fallback for systems that don't have a kernel event mechanism like
inotify or kqueue.
Usage
When you run './configure && make && make install', pnotify is built
as a shared library and installed under the /usr/local prefix.
Even though pnotify is built as a shared library by default, it is
easier for application developers to include pnotify.c and pnotify.h
in their source tree and not depend on the existence of a shared
library.
Download
The source code may be downloaded from the [6]download page. You may
also check out a working copy of the latest development sources by
issuing the following command:
svn checkout http://pnotify.googlecode.com/svn/trunk/ pnotify
If you just want a quick peek at the source code, you can browse the
[7]webSVN repository
Documentation
* The pnotify(3) manpage in [8]HTML or [9]PostScript format.
* Doxygen-generated API reference manual (coming soon)
Mailing List
There is a mailing list for discussion about the pnotify library.
Click [10]here to sign up, post a question or comment, or browse
through the archives.
Contact the Author
For more information, contact Mark Heily at [11]devel@heily.com
Related Links
* [12]FAM - the original, unmaintained monitoring utility from SGI.
* [13]gamin - the modern FAM replacement. Part of the GNOME project.
* [14]libevent - a library for building event-driven servers.
Supports socket events, but not filesystem events.
_________________________________________________________________
(C) 2007 Mark Heily.
References
1. file://localhost/pnotify/manpage.html
2. http://linux.die.net/man/7/inotify
3. file://localhost/pnotify/index.html#download
4. file://localhost/pnotify/index.html#docs
5. file://localhost/pnotify/index.html#mlist
6. http://code.google.com/p/pnotify/downloads/list
7. http://pnotify.googlecode.com/svn/trunk/
8. file://localhost/pnotify/manpage.html
9. file://localhost/pnotify/manpage.ps
10. http://groups.google.com/group/pnotify/topics
11. mailto:devel@heily.com
12. http://oss.sgi.com/projects/fam/
13. http://www.gnome.org/~veillard/gamin/
14. http://monkey.org/~provos/libevent/
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