Re: Feature request: rm should implement option -p, --parents

[Guido Flohr]

Hi Pádraig,

Pádraig Brady wrote:
> > Uninstalling with clean up in such cases is a frequent task, and could be 
> > greatly simplified by:
> >
> >     $ rm --parents /usr/share/myapp/pixmaps/8x16/icon.png
> >     rm: failed to remove `/usr/share': Directory not empty
> >     $ ls /usr/share/myapp
> >     ls: cannot access /usr/share/myapp: No such file or directory
> >
> > The idea is to remove the containing directory of a file recursively, upwards, 
> > and stop that recursion on the first failure to remove a directory, most 
> > probably because of ENOTEMPTY.
>
> Would that not be better supported with:
>
> rm "$dir/icon.png" && rmdir -p "$dir"
>
> I can kind of see the benefit of your proposal in the
> unusual case where $dir is not known. But then one can do:
>
> rm "$file" && rmdir -p $(dirname "$file")

Sure.  But compare that to:

    rm -p $file

Clearer and more efficient to boot.

The case where the directory part is not known is quite frequent imho. 
I configured a random GNU package (in this case gettext from the current 
git sources), configured it with "--prefix=/tmp/my_gettext", then 
"make", "make install", and "make uninstall", and finally ran find over 
the directory /tmp/my_gettext.  It finds 194 directories and one regular 
file (/tmp/my_gettext/share/info/dir, but that is a nuisance of its 
own).  So not even packages that use GNU autoconf clean up after 
themselves.  Now imagine you had to implement a cleanup mechanism.  With 
"rm -p" you would simply do one check whether rm understands "-p", and 
then write to your Makefile:

    RM = /bin/rm -p

And voilà, at least on recent enough systems that implement the option 
already.

Next example is Perl.  You cannot uninstall the interpreter itself, when 
built from sources, and additional Perl modules follow this bad example, 
and simply spit out some pseudo Perl code for "make uninstall" with 
"what would be done":

     unlink /usr/lib/perl5/site_perl/5.8.8/i686-linux/auto/My/Pack.so
     unlink /usr/lib/perl5/site_perl/5.8.8/i686-linux/auto/My/Pack.bs
     # 357 lines following

It is trivial to pipe that into "sed -e 's,unlink,rm -p,' | /bin/sh" (I 
do that all the time without -p).  But how many people will find the 
syntactically correct command pipe for your version? Yes, sure, there is 
also the "xargs -0" problem, ... I simplified things.

Did you ever unpack a tarball at the wrong location? Was it a nightmare? 
What about this instead:

    tar tf ball.tar | xargs rm -p

You can find a solution for all of these cases, but wouldn't adding the 
option "-p" to the rm utility help a lot of people with less knowledge 
and experience than you to keep their file systems cleaner?

> > The same idea could be applied to chmod, chgrp, and chown.
>
> So you mean assume empty directories above the file belong with
> the file, and so change the permissions and ownership accordingly.
> Would that not be better supported with `install -d` ?

No, what I mean is this:

    $ ls /path/to/some/file/in/a/deep/directory/structure.sth
    ls: Cannot access `...': Permission denied
    $ sudo chmod g+rx /path
    $ sudo chmod g+rx /path/to
    ...
    $ sudo chmod g+rx /path/to/some/file/in/a/deep/directory

That does not happen every day, but when you need it, a single

    $ sudo chmod -p g+rx /path/to/some/file/in/a/deep/directory

would come in handy.  Do a phrase search for "chmod -R 777" in your 
favorite search engine.  I think that beginners often make their system 
less secure than necessary because they cannot deal with error messages 
they do not understand immediately.  If you want to remedy such 
situations, it is a more conservative approach to manipulate a path to a 
certain node, than to manipulate entire subtrees.  But most utilities do 
not provide that option.

Cheers,
Guido
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