Filesystem Watch with PyQt4

qfsw = QtCore.QFileSystemWatcher()
qfsw.addPaths([path1, file2 ... ])

QtCore.QObject.connect(qfsw,QtCore.SIGNAL("directoryChanged(QString)"),function)
QtCore.QObject.connect(qfsw,QtCore.SIGNAL("fileChanged(QString)"),function)

# !/usr/bin/env python
#
# Runs a command when a file system change occurs in specified list of paths.
#
# (c) Copyright 2008, Mathieu Leplatre,
#
# This software may be used and distributed according to the terms
# of the GNU Public License, incorporated herein by reference.

import sys, os
from PyQt4 import QtCore, QtGui
import signal
from optparse import OptionParser

# Parse command-line options
usage = """Usage: %prog [options] COMMAND PATHS
Run COMMAND when a file system change occurs in specified list of PATHS.

COMMAND can contain '%s' to refer changed file or directory."""

parser = OptionParser(usage, version="%prog 1.0")
(options, args) = parser.parse_args()
if len(args) < 2:
    parser.print_help()
    sys.exit(2)

# Command
command = args[0]
# List of paths
paths = args[1:]


def onFileSystemChanged(path):
    """
    Callback when file or folder change
    @param path : Changed path
    @type  path : string
    """
    global command
    # Execute command replacing %s with path:
    if '%s' in command:
        command = command % path
    # Run as different process
    print "Run '%s'..." % command
    if os.fork() == 0:
        os.system(command)
        sys.exit(0)


def main():
    app = QtGui.QApplication(sys.argv)

    # Set up file system watcher
    qfsw = QtCore.QFileSystemWatcher()
    qfsw.addPaths(paths)
    QtCore.QObject.connect(qfsw,QtCore.SIGNAL("directoryChanged(QString)"),onFileSystemChanged)
    QtCore.QObject.connect(qfsw,QtCore.SIGNAL("fileChanged(QString)"),onFileSystemChanged)

    # Allow program to be interrupted with Ctrl+C
    signal.signal(signal.SIGINT, signal.SIG_DFL)

    # Qt Main loop
    sys.exit(app.exec_())


if __name__ == "__main__":
    main()