zsh change dir after hook w/`chpwd_functions`

How does rvm work? You change to a directory and rvm has determined which version of ruby you're using.

In bash, the cd command is overriden with a cd function. This isn't necessary in zsh because zsh has hooks that execute after you change a directory.

If you have rvm installed in zsh you'll see this:

> echo $chpwd_functions
__rvm_cd_functions_set
> echo ${(t)chpwd_functions}
array

chpwd_functions is an array of functions that will be executed after you run cd.

Within the function you can use the $OLDPWD and $PWD env vars to programatically determine where you are like this:

> huh() { echo 'one sec...' echo $OLDPWD && echo $PWD } 
> chpwd_functions+=huh
> cd newdir
one sec...
olddir
newdir

You can read more about hook functions in the zsh docs.

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