On Mon, 14 Dec 2009 12:21:12 +0000
Marc Herbert <marc.herb...@gmail.com> wrote:
> Matias A. Fonzo a écrit :
> > On Fri, 11 Dec 2009 16:16:13 +0000
> > Marc Herbert <marc.herb...@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.
>
The [ -L "foo" -a ! -e "foo" ] is a specific case to check dangling 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.
>
Is just an example.
> 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>
>
Yeah logic.. I have intuition.
Regards,
Matías
