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capn allows you to specify hooks when changing directories
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capn is a package that provides hooks when the current-working-directory changes.


$ sudo pip install capn
$ touch ~/.capnhooks


capn uses a simple YAML file for specifying paths and their hooks. As a quick example, consider the following:

   default_type: path
     - ~/.otherhooks
  - path: /home
    type: tree
      - echo entering /home
      - echo exiting /home
      - echo /home waves goodbye

  - path: ~/
      - echo entering ~/
      - echo exiting ~/

The above establish enter and exit hooks for the two listed directories. As you change directories you should see output indicating each hook's execution. You'll notice that the /home path has a type key with the value tree. There are two types of hooks; path, which is the default, only triggers for that absolute path. tree hooks will trigger when you enter or leave the tree below the specified path. Moving between child-paths below the tree does not trigger the hooks. For example, moving from / -> /home would trigger the enter hook. Moving from /home -> ~/ would not trigger the exit hook.

Generally the commands specified in the hooks will be the names of shell scripts not single shell commands.

The first section of the configuration currently has two available settings:

  • default_type: either path or tree. If setting is not specified, path will be used.
  • external_hooks: a list of paths to other YAML files containing additional hooks. Such files should resemble the 'hooks' section of the above example configuration.


After installing capn you will need to source:

$ source capn

If you no longer wish to have the hooks activated:

$ unhook


add_external_hook(filename, path, hooktype=DEFAULT_TYPE, 
                  enter=[], exit=[]):

Currently capn has a minimal API with a single function that is used to manage programmatically generated external hook files. See the example below:

>>>from capn.config import add_external_hook
>>>filename = "~/.otherhooks"
>>>path = ~/projects/foo/bar
>>>hooktype = 'tree'
>>>enter = ['source ~/projects/foo/bar/bin/activate']
>>>exit = ['deactivate']
>>>add_external_hook(filename, path, hooktype=hooktype,
...                  enter=enter, exit=exit)

The above will add a hook to auto de/activate the python-virtualenv whenever the shell is inside the project directory to the file "~/.otherhooks". You will then need to add the filename to the external_hooks list in the "~/.capnhooks" configuration file.

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