Re: chmod

["Gary Hennigan" <glhenni@sandia.gov>]

"Daniel D Jones" <ddjones@riddlemaster.org> writes:
> I've been using Linux for awhile but every thing I know is self taught.  That
> means I know some things quite well and am abysmally ignorant in other areas.
> Hopefully, this question isn't too stupid.  Or maybe it'll give you a good
> laugh and you'll take pity on me and answer anyway!
> 
> I want to set specific permissions on a group of directories and all
> sub-directories.  I can't figure out how to do this other than manually
> tracing through the directory tree.
> 
> As near as I can tell, chmod has no option to select only directories.  I
> figured I'd use ls to list the directories and pipe them to chmod, but ls
> doesn't seem to be able to do it either.  Surely I'm missing something.  ls
> _has_ to have the equivalent of the DOS command "dir /a:d".  Doing "info ls",
> "Which files are listed" shows only -a, -A, -B, -d, -I, -L, -R, none of which
> seem to be able to suppress listings based upon permissions or types.
> 
> The closest I could figure out was to do:
> 
> ls | grep ^d
> 
> However, trying to use that method to extract only the directory names and
> then pipe them to chmod would have gotten quite convoluted.
> 
> So, the primary question is, is there an easy way to set the permission on
> directories, only directories, and all sub-directories?  A related question
> is how to use ls to list only directories.

Well, in Unix you typically string a bunch of simple tools together to
accomplish complex tasks. You almost had it with your "ls" solution,
but try "find" instead, and use xargs. Here's how I do what you're
trying to accomplish:

        find <dirname> -depth -type d -print|xargs chmod 770

> And if anyone's in a 'splaining mood, here's another one: how do you set all
> files so that the group permissions match the user permissions?  (If you have
> three files who's permissions are, for example, 700, 600, 500, and you want
> them to be 770, 660, 550 respectively.)

This one is tougher, I think. I'd write a script to do it. Maybe
someone has a brighter idea. The complication here is that there's not
a good shell command, or unix utility, to simply report the mode of a
file in numerical form, at least that I'm aware of. You could write
such a utility pretty easily in C using the "stat()" function, but
even though it's simple it seems like over kill. Gotta be a better
way.

Gary


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