Path: utzoo!utgpu!watserv1!watmath!att!rutgers!usc!elroy.jpl.nasa.gov!jpl-devvax!lwall
From: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Newsgroups: comp.unix.questions
Subject: Re: Deleting directories
Message-ID: <8673@jpl-devvax.JPL.NASA.GOV>
Date: 10 Jul 90 17:44:15 GMT
References: <37481@ucbvax.BERKELEY.EDU>
Reply-To: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 38

In article <37481@ucbvax.BERKELEY.EDU> ashish@janus.Berkeley.EDU.UUCP (Ashish Mukharji) writes:
: Recently, I had to remove all of a user's files older than a 
: certain date.  That was easily accomplished with find(1), but deleting the 
: resulting (empty) directory structure presents a greater problem.  The user's 
: home directory is the root of a large, mostly empty directory tree.  I want
: to delete all directories that do not contain any regular files - find starts
: with . and works its way down (inorder).  What I need is a way to do a 
: postorder traversal of the directory structure.  Is there a simple way, short 
: of writing a C routine?

With regard to getting the directories in the right order, some find programs
have a -depth switch to do this.  Otherwise, pipe the output through sort -r.
Then you have to wrap something around to do the rmdir:

If there aren't too many:
    rmdir `find . -type d -print | sort -r`

If you have xargs:
    find . -type d -print | sort -r | xargs rmdir

If you have Perl:
    find . -type d -print | sort -r | perl -ne 'chop; rmdir;'

Using sh:
    find . -type d -print | sort -r | while read dir; do rmdir $dir; done

Using sed:
    find . -type d -print | sort -r | sed 's/^/rmdir /' | sh

With all but one of these, you'll have to ignore the error messages on
directories that can't be removed.  (Where ignoring may consist of >&/dev/null
or 2>/dev/null, depending on your culture (or lack thereof :-).)

The perl solution will be most efficient if you have the rmdir system call.
Otherwise the xargs solution will probably be best.

Larry Wall
lwall@jpl-devvax.jpl.nasa.gov