alarm

Synopsis

my $remaining = alarm(30);   # fire SIGALRM in 30 seconds
alarm(0);                    # cancel any pending alarm

Description

Schedules a SIGALRM signal to be delivered after a given number of seconds.

Arranges for a SIGALRM to be delivered to the process after the specified number of seconds. If an alarm was already pending, the old alarm is cancelled and the number of seconds that were remaining is returned. Calling alarm(0) cancels the current alarm without setting a new one.

Commonly used with eval/die or $SIG{ALRM} to implement timeouts:

eval {
    local $SIG{ALRM} = sub { die "timeout\n" };
    alarm(10);
    # ... long operation ...
    alarm(0);
};

Negative values are clamped to 0.

See also

sleep, alarm, POSIX