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Call a command when a directory changes. (Mac OS only)

Project description

icemac.callonchange calls a specific command when a directory or something in it has changed. It was developed to ease test driven development (TDD): it can call the test case under development each time the test case or the developed code changes.


  • Mac OS X 10.5+ (Leopard)
  • Python 2.5

General usage

Usage: callonchange [options] path utility [utility arguments]

coc invokes utility with its utility arguments when path or something in it changes.

-h, --help show this help message and exit
-e EXTENSION only call utility on changes of a file with this extension (option might be used multiple times)

EXTENSION might be specified with or without leading dot:

-e .py is equal to -e py

Caution: optional arguments must be specified before the positional arguments (path and utility). Arguments specified after the positional arguments are taken as arguments of the utility.

Usage as script


To install callonchange as script call:

$ python install

or install it using a package manager like easy_install or pip.

Call as script

To call it as a script add the path to the directory to be observed and the command (script or program) to be called when the directory or something in it has changed.

Example to call xeyes when a file with the extension log has changed in /var/log enter:

$ callonchange -e log /var/log xeyes

Caution: In this example xeyes is called on every new entry in the log file.

In buildout

There is a recipe in the package which eases installation using buildout.

Installation with default arguments

Add a section to your buildout to generate a script for callonchange (don’t forget to add it to the parts!):

recipe = icemac.callonchange

This creates a callonchange script with default arguments. These are:

'-e', 'py', '-e', 'zcml', '-e', 'pt', '-e', 'txt', 'src', 'bin/test', '-cv'

Which means: observe in the src directory files with the extensions py, zcml, pt and txt. Call bin/test with the arguments cv (verbose and color) on changes.

Installation with customized arguments

To override the default arguments add an arguments parameter to the buildout section:

recipe = icemac.callonchange
name = coc
arguments = 'Products', 'bin/ztest'

This means: The created script will be named coc. When called it will observe the Products directory and call bin/ztest on changes.

Usage as buildout script

You can add additional parameters when you call the generated script:

$ bin/callonchange -t testObserver

When you use the default arguments in the buildout section, this command line calls bin/test -cv -t testObserver on each change of py, zcml, pt or txt files in the src directory.

Stopping callonchange

To stop a running callonchange instance hit ^C (Control-C).

Runing the tests

To run the tests of icemac.callonchange call:

$ python test

or use buildout:

$ python
$ bin/buildout
$ bin/test

or use callonchange itself:

$ python
$ bin/buildout
$ bin/callonchange

In the last version you have to change something inside the src directory of the package so the observer lets the tests run.


Thanks to Malte Borch for the great MacFSEvents which icemac.callonchange is based on.


  • It would be nice to have predefined argument lines (profiles) even when not using buildout. They could be stored in the home directory of the user. (Should support profiles which reverence other profiles.)
  • In buildout recipe: default script name should be section name.


0.3.1 (2010-07-10)

  • Fixed incorrect handling of the find-links buildout parameter.

0.3 (2010-07-07)

  • Added abbility to specify file extensions so only files with these extensions will be observed.
  • Added a name parameter to the recipe to control the name of the generated script, e. g. allowing more than one icemac.callonchange script in a buildout.

0.2 (2010-07-04)

  • Added buildout recipe to ease integration with buildout projects. (See section In buildout.)

0.1 (2010-07-02)

  • Initial release.

Project details

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