Question

I frequently use the following pattern to set an upper bound to the running time of a particular code fragment in Perl:

my $TIMEOUT_IN_SECONDS = 5;
eval {
    local $SIG{ALRM} = sub { die "alarm\n" };
    alarm($TIMEOUT_IN_SECONDS);
    # do stuff that might timeout.
    alarm(0);
};
if ($@) {
    # handle timeout condition.
}

My questions:

• Is this the right way to do it?
• Are there any circumstances under which the running time can exceed $TIMEOUT_IN_SECONDS, or is the above method bullet-proof?

Answer 1

You probably want to look at Sys::SigAction. I haven’t used it myself, but it has some glowing reviews.

One thing to watch out for is if “stuff that might timeout” uses sleep or alarm itself. Also, in the error handling code, I assume you’re prepared for errors other than a timeout.