On Sun, 2008-02-17 at 16:40 -0800, Andrew Farris wrote: > Behdad Esfahbod wrote: > >> On Sun, 17 Feb 2008 08:15:20 -0800, Arjan van de Ven wrote > >> > >>>> This should really be fixed in bash to short-circuit. > >>> well......... not sure it can be done in the bash language. > >>> (it may well guarantee that both get executed) > > > > There's nothing to execute there. All the expansions happen first, so > > if you have things like [ -n "$something" -a "`id`" = 0 ], the `id` call > > is made before passing control to "test". The short-circuit would just > > happen in the evaluation in test. There's no user-visible difference > > there. > > If thats the case shouldn't a statement like that always be nested so that `id` > is not called if it is not necessary, possibly saving many disk accesses? It > would seem that using the more complex constructs could be much slower if all > the cases are evaluated before testing any of them. I believe that's correct. The initial case that Arjan brought up though was [ -f somefile -a -f anotherfile ]. That doesn't have this problem. /me is surprised that this kind of micro-optimizing has such drastic effects that Arjan has measured. -- behdad http://behdad.org/ "Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety." -- Benjamin Franklin, 1759 -- fedora-devel-list mailing list fedora-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-devel-list
