Re: best way to test for empty dir?
Matias A. Fonzo a écrit :
On Fri, 11 Dec 2009 16:16:13 +
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.
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 -Lboundedness
http://en.wikipedia.org/wiki/Boolean_logic#Properties
Re: add a way to declare global variables
Bernd Eggink a écrit : To avoid misunderstandings, let me add that you are right (only) with respect to variables being used _without_ declaration. OK, but not having to explicitly declare variables is a feature that most people expect from dynamic languages, so you can hardly blame them for doing this all the time in shell. IMHO Python gets this global/local (implicit) declaration story right. Of course it is easier when you do not have 30 years of POSIX legacy to support (but just the experience). http://docs.python.org/tutorial/controlflow.html#defining-functions
Re: add a way to declare global variables
Am 12/14/09 13:37, schrieb Marc Herbert: Bernd Eggink a écrit : To avoid misunderstandings, let me add that you are right (only) with respect to variables being used _without_ declaration. OK, but not having to explicitly declare variables is a feature that most people expect from dynamic languages, so you can hardly blame them for doing this all the time in shell. I don't blame anybody. I'm talking about the fact that associative arrays are an exception from what most people expect from dynamic languages, as they _have_ to be explicitly declared. This doesn't bother me, but I would prefer to have a choice between local and global declaration anyway. -- Bernd Eggink http://sudrala.de
Re: best way to test for empty dir?
On Mon, 14 Dec 2009 12:21:12 +
Marc Herbert marc.herb...@gmail.com wrote:
Matias A. Fonzo a écrit :
On Fri, 11 Dec 2009 16:16:13 +
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 -Lboundedness
http://en.wikipedia.org/wiki/Boolean_logic#Properties
Yeah logic.. I have intuition.
Regards,
Matías
