Getting UNIX prompt to display current directory

[ilan343 at violet.berkeley.edu]

In article <5582 at ncsugn.ncsu.edu> fristens at ncsugn.ncsu.edu (Brian Fristensky) writes:
>In MS-DOS there is a very easy way to get the current directory displayed as
>part of the prompt  (prompt $p).  In UNIX, there is certainly no
>straightforward way to do this.  Can anyone think of a tricky way?  My
>guess is that it would involve getting pwd output into the shell variable
>$PS1, but that would require somehow getting pwd to execute after each
>command you type. 

I use an idea plagiarized from a contribution by Daniel Bauer to the
Wizard's Grabbag (UnixWorld-August 1988). It creates a function to
replace "cd".  Everytime you change directory, PS1 is redefined.
It also changes the prompt whenever a sub-shell is open, keeping count
of what level your are.