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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)


icemac.callonchange can be used as standalone script and in buildout.

Usage as script


To install icemac.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 something changed in the Downloads directory enter:

$ callonchange ~/Dowloads xeyes

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 icemac.callonchange (don’t forget to add it to the parts!):

recipe = icemac.callonchange

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

'src', 'bin/test', '-cv'

Which means: observe the src directory and call bin/test with the arguments 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
arguments = 'Products', 'bin/ztest'

This means: 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 in the src directory.

Stopping icemac.callonchange

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

Run tests

To run the tests of icemac.callonchange call:

$ python test

or use buildout:

$ python
$ bin/buildout
$ bin/test

or use icemac.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.

To do

  • Ease buildout integration by providing a buildout recipe with default arguments.
  • icemac.callonchange is currently not useable in situations where the command changes something in the observed diretory. (e. g. LaTeX documents can’t be created with it as the creation changes the observed diretory which starts creation … over and over again. (Need an ability to select file extension(s) for which the command should be run.)


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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