onchange.py

#!/usr/bin/python
# Monitors file changes and runs programs on them.
# Needs pyinotifyx.

import os, sys, subprocess
from inotifyx import init, add_watch, IN_CLOSE_WRITE, get_events, rm_watch

help_text="""\
This program monitors some files and runs some commands if one is modified.
For example, to interactively view the pdf of a latex file, start:
  $ onchange.py *.tex -- latex %f
%f in the commands is replaced by the modified filename, %b with its basename.
It is possible to state several files to watch. Likewise, several commands can be stated, they are executed successively until one fails.

Synopsis
""" + "$ %s file1 ... -- command1 ..."%sys.argv[0]

if __name__ == "__main__":

    if "--" not in sys.argv:
        print help_text
        sys.exit(1)


    minus_ix  = sys.argv.index("--")
    filenames = sys.argv[1:minus_ix]
    commands  = sys.argv[minus_ix+1:]

    print
    print "Filenames:", ", ".join(filenames)
    print "Commands: ", ", ".join(commands)

    filedict = {}
    fd = init()

    def add_watch_to_file_dict(filename, wd=None):
        if wd and wd in filedict:
            del filedict[wd]
        filedict[add_watch(fd, filename, IN_CLOSE_WRITE)] = filename

    try:
        for filename in filenames:
            add_watch_to_file_dict(filename)
        while 1:
            for event in get_events(fd):
                print 80 * '-'
                filename = filedict[event.wd]
                print "--", filename
                (basename, ext) = os.path.splitext(filename)
                for cmd in commands:
                    filled_cmd = cmd.replace('%f', filename).replace('%b', basename)
                    print ">>", filled_cmd
                    sp = subprocess.Popen(filled_cmd, shell=True,
                        stdout=subprocess.PIPE, stderr=subprocess.PIPE)
                    output = sp.stdout.read() + sp.stderr.read()
                    if sp.wait() > 0:
                        subprocess.call(["kdialog", "--error", output])
                        break
                add_watch_to_file_dict(filename, event.wd)
    except KeyboardInterrupt:
        pass
    finally:
        for wd in filedict:
            try: rm_watch(fd, wd)
            except: pass
        os.close(fd)

This program monitors some files and runs some commands if one is modified.
For example, to interactively view the pdf of a freemind mindmap, start:
$ onchange *.tex -- latex --jobname=%b %f
%f in the commands is replaced by the modified filename, %b with its basename.