信号量作为锁使用事例。

#!/usr/bin/perl
#
use strict;
use IPC::Semaphore;
use IPC::SysV qw(IPC_PRIVATE S_IRUSR S_IWUSR IPC_CREAT IPC_NOWAIT SEM_UNDO);

our $sem = IPC::Semaphore->new(IPC_PRIVATE, 1, S_IRUSR | S_IWUSR | IPC_CREAT);
$sem->setval(0,1);
my $pid = fork();
die "fork failed" unless defined $pid;
if ($pid > 0) {
	$sem->op(0,-1,SEM_UNDO);
	my $i = 10;
	while($i > 0){
		print "parent process i= $i\n";
		$i--;
	}
	$sem->op(0,1,SEM_UNDO);
} elsif ($pid == 0){
	$sem->op(0, -1, SEM_UNDO);
	my $i = 10;
	while($i > 0) {
		print "child process i = $i\n";
		$i--;
	}
}
$sem->remove() if defined $sem;

 

-> # ./testsem.pl
parent process i= 10
parent process i= 9
parent process i= 8
parent process i= 7
parent process i= 6
parent process i= 5
parent process i= 4
parent process i= 3
parent process i= 2
parent process i= 1
child process i = 10
child process i = 9
child process i = 8
child process i = 7
child process i = 6
child process i = 5
child process i = 4
child process i = 3
child process i = 2
child process i = 1