Watch for Coffeescript or Less files in your project tree and compile them on save.

watcher.py

#!/usr/bin/env python

import os, time
import optparse
import subprocess

def watch(watchpath, delay=1):
    """\
    recursively iterates over files in a directory tree and watches for the ones that have been changed
    returns an infinite iterator object containing filenames of changed files
    """
    watched_files = {}
    while True:
        for root, dirnames, filenames in os.walk(watchpath):
            for file in filenames:
                path = os.path.join(root, file)

                try:
                    mod_time = os.stat(path).st_mtime
                except OSError: # inaccessible
                    continue

                try:
                    if watched_files[path] < mod_time:
                        yield path
                except KeyError:
                    pass

                watched_files[path] = mod_time

        time.sleep(delay)

if __name__ == '__main__':
    commands = {
        '.less': 'lessc {file}.less > {file}.css',
        '.coffee': 'coffee -c {file}.coffee',
        # add more
    }

    usage = 'usage: %prog [options] PATH'
    parser = optparse.OptionParser(usage=usage, description='Less CSS and Coffeescript compilig automator')
    parser.add_option('-d', '--delay', type=int, default=1, help='polling interval in seconds')
    parser.add_option('-q', '--quiet', action='store_true', default=False, help='turn off informational messages')

    options, args = parser.parse_args()
    watchpath = '.' if not args else args[0]

    try:
        for file in watch(watchpath, options.delay):
            basename, extension = os.path.splitext(os.path.abspath(file))
            try:
                command = commands[extension].format(file=basename)
                if not options.quiet: print('envoking compiler for {file}:\n{command}'.format(file=file, command=command))
                ret = subprocess.call(command, shell=True)
                if not options.quiet: print('\033[92m[success]\033[0m' if not ret else '\033[91m[failed]\033[0m')
            except KeyError: # command not defined
                pass
    except KeyboardInterrupt:
        if not options.quiet: print('\n\033[94m[end]\033[0m')