Automatic script execution

On Dir is a program that automatically executes scripts as you traverse directories at a terminal.

Example usage:

alec@cavern:~$ umask
alec@cavern:~$ cd public_html
alec@cavern:~/public_html$ umask
alec@cavern:~/public_html$ cd
alec@cavern:~$ umask

The above is accomplished with the help of ondir, some scripts added to the users (or system) startup scripts and an entry in my ~/.ondirrc for the ~/public_html path.

The entry in my ~/.ondirrc would look like this

enter /home/athomas/public_html
  umask 022

leave /home/athomas/public_html
  umask 077

In addition to executing scripts in the directory you are entering or leaving, ondir also executes scripts in directories that are traversed on the way to that directory. For example, if you are in your home directory and type:

$ cd ~/public_html/myproject

On Dir scripts for ~/public_html and ~/public_html/myproject are executed because these directories are traversed. You can download On Dir from the bottom of this page.

Tips and Tricks

On Dir has acquired a couple of very nice features over the years, here are a couple. Tilde expansion in paths.

enter ~/public_html
  umask 022
leave ~/public_html
  umask 077

Expansion of environment variables in the form $VAR or ${VAR}.

The environment variable $ONDIRWD is always set to the directory being traversed. This is not equivalent to $PWD, as $PWD is the destination directory, whereas $ONDIRWD is the directory that matched during path traversal.

enter $HOME/public_html:/opt/movies
  echo "You have traversed $ONDIRWD"

Multiple paths per section.

enter /opt/movies:/opt/music
  umask 007
leave /opt/movies:/opt/music
  umask 077

Regular expressions, including sub-pattern capturing and referencing (sub-patterns are assigned to the environment variables $0 through $9).

enter ~/projects/(ondir|todo)
  echo "Welcome to $1"
leave ~/projects/(ondir|todo)
  echo "Thanks for visiting $1"