Re: best way to test for empty dir?

[Marc Herbert]

Matias A. Fonzo a écrit :
> On Fri, 11 Dec 2009 16:16:13 +0000
> Marc Herbert <Marc.Herbert@gmail.com> wrote:

>> In case anyone is interested my winner (so far) is:
>>
>> exists()
>> {
>>     [ -e "$1" -o -L "$1" ]
>> }
>>
> 

> The -L is redundant.

Not for me. I need -L because I want to consider broken symlinks just
like anything else. A broken symlink would be a bug in my code and I want to
detect it ASAP.


> Because, if the symlink is not broken, the regular file "exists" ( -e ).

Please forget about correct symlinks. The -L is here for *broken*
symlinks.


> A solution to check the broken symlink is:
> 
> [ -e "foo" -o -L "foo" -a ! -e "foo" ]

For which type of "foo" object does this return a different value than
the above? None.

If common sense is not enough, here is a formal proof that your third
and last test is redundant:

  -e or (-L and ! -e)  == (-e or -L) and (-e or ! -e)  distributivity
                          (-e or -L) and 1             complements
                           -e or -L                    boundedness

<http://en.wikipedia.org/wiki/Boolean_logic#Properties>