16.20.1. Problem

16.20.2. Solution

To block a signal around an operation:

use POSIX qw(:signal_h);

$sigset = POSIX::SigSet->new(SIGINT);    # define the signals to block
$old_sigset = POSIX::SigSet->new;        # where the old sigmask will be kept

sigprocmask(SIG_BLOCK, $sigset, $old_sigset)
    or die "Could not block SIGINT\n";

To unblock:

defined sigprocmask(SIG_UNBLOCK, $old_sigset)
    or die "Could not unblock SIGINT\n";

16.20.3. Discussion

The POSIX standard introduced sigaction and sigprocmask to give you better control over how signals are delivered. The sigprocmask function controls delayed delivery of signals, and sigaction installs handlers. If available, Perl uses sigaction when you change %SIG.

To use sigprocmask, first build a signal set using POSIX::SigSet->new. This takes a list of signal numbers. The POSIX module exports functions named after the signals, which return their signal numbers.

use POSIX qw(:signal_h);

$sigset = POSIX::SigSet->new( SIGINT, SIGKILL );