Re: Why is command substitution happening?

[Greg Wooledge]

On Mon, Apr 11, 2011 at 12:23:15PM -0600, Bill Gradwohl wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> 
> I have a tiny script to prune empty directories from a structure. The
> essential line is as follows:
> 
> tree --noreport -dfi "${1}" | tac | sed 's/"/\\"/g;s/^/rmdir
> - --ignore-fail-on-non-empty "/;s/$/"/'|bash

Not good.  You're piping filenames into bash and letting bash parse them
as commands.  If a filename contains something like $(...) or `...` then
yes, bash would perform a command substitution.

Just do this instead:

  find . -type d -exec rmdir {} \; 2>/dev/null

It's a bit of a hack; it relies on the fact that rmdir will fail on
non-empty directories, so we don't have to CHECK them.  It discards
all errors, which is the hackish part.  If this isn't good enough,
learn find in more depth.

  http://mywiki.wooledge.org/UsingFind