Running a script whenever another script runs, or modifying a package script

Question

I have a two part question. First, is there a method to run a script whenever another (particular) script runs?

Secondly, I have created a script which I am using to 'override' the package 'cd' script, however, I've done this using aliases, and I'm wondering if there is a better (more proper) way to do this, or for that matter if my method will cause any errors done the road.

Allow me to explain my script... whenever "cd" is asked to move to a non-existent directory, it would than give the user the option to relocate the the 'deepest' existent directory in the entered path. It would be easier with an example...

Say I entered:

cd /var/www/html/foo

and that /var/www/html/foo does not exist, but /var/www/html does. the user would than be asked if they would like to proceed to /var/www/html.

I was able to make this happen using an alias and the following script:

   #!/bin/bash
   cd $*
   <code to check if valid, et cetera>

However, this is done by using

   alias cd='cdImproved'

As such, I'm uncertain if I will run into any problems doing this done the road, or if there is a more 'proper' way of doing the same thing.

Answer 1

I'm assuming that this cd &* is a typo and you mean this: cd $*. Also, this should not have any spaces around the equal sign: alias cd='cdImproved'.

You can't cd in a script that you run normally and have the new directory be set for the current shell. You have to use an alias, a function or source the script.

You can certainly define your function or alias in a file and source that in each script that you want to have make use of it. That would be the way to go. Since cd is a shell builtin, you'd have to modify the shell or create a loadable builtin to change its behavior globally.

To use aliases inside a script you'll have to turn on that feature in the script:

shopt -s expand_aliases