On Mon, Jul 13, 2009 at 22:57, Jenn G.<practicalp...@gmail.com> wrote:
> Hello,
>
> From the code below:
>
> eval {
> local $SIG{ALRM} = sub { die "TIMEOUT\n" };
> alarm($seconds);
> ... code to execute with timeout here ...
> alarm(0); # cancel alarm (if code ran fast)
> };
> alarm(0); # cancel alarm (if eval failed)
>
>
> Is the second alarm(0) needed or not?
> In my before experience, I used only one alarm(0) in eval { }.
snip
Then you have opened yourself up to problems:
#!/usr/bin/perl
use strict;
use warnings;
eval {
local $SIG{ALRM} = sub { die "timeout\n" };
alarm 1;
die "oops";
alarm 0;
};
select undef, undef, undef, 2;
print "no problem\n";
I typically write it like this:
#!/usr/bin/perl
use strict;
use warnings;
sub timeout {
my ($wait, $code, $timedout, $error) = (@_,
sub { warn $@ }, sub { die $@ });
eval {
local $SIG{ALRM} = sub { die "timeout\n" };
alarm $wait;
$code->();
alarm 0;
1;
} or do {
alarm 0; #ensure that alarm is not still set
#raise error if it isn't a timeout
if ($@ eq "timeout\n") {
$timedout->();
} else {
$error->();
}
};
}
timeout 1,
sub { die "oops\n" },
sub { warn "timeout out\n" },
sub { warn "died with $@" };
timeout 1,
sub { select undef, undef, undef, 2 },
sub { warn "timeout out\n" },
sub { warn "died with $@" };
timeout 1,
sub { print "normal execution\n" },
sub { warn "timeout out\n" },
sub { warn "died with $@" };
timeout 1, sub { select undef, undef, undef, 2 };
timeout 1, sub { die "and here it ends" };
--
Chas. Owens
wonkden.net
The most important skill a programmer can have is the ability to read.
--
To unsubscribe, e-mail: beginners-unsubscr...@perl.org
For additional commands, e-mail: beginners-h...@perl.org
http://learn.perl.org/
