使用mmap实现进程间通信

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

int main(void)
{
	const char str1[] = "string 1";
	const char str2[] = "string 2";
	int parpid = getpid(), childpid;
	int fd = -1;
	char *anon, *zero;

	if ((fd = open("/dev/zero", O_RDWR, 0)) == -1)
		err(1, "open");

	anon = (char*)mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0);
	zero = (char*)mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_FILE|MAP_SHARED, fd, 0);

	if (anon == MAP_FAILED || zero == MAP_FAILED)
		errx(1, "either mmap");

	strcpy(anon, str1);
	strcpy(zero, str1);

	printf("PID %d:\tanonymous %s, zero-backed %s\n", parpid, anon, zero);
	switch ((childpid = fork())) {
		case -1:
			err(1, "fork");
		case 0:
			childpid = getpid();
			printf("PID %d:\tanonymous %s, zero-backed %s\n", childpid, anon, zero);
			sleep(3);

			printf("PID %d:\tanonymous %s, zero-backed %s\n", childpid, anon, zero);
			munmap(anon, 4096);
			munmap(zero, 4096);
			close(fd);
			return EXIT_SUCCESS;
	}

	sleep(2);
	strcpy(anon, str2);
	strcpy(zero, str2);

	printf("PID %d:\tanonymous %s, zero-backed %s\n", parpid, anon, zero);
	munmap(anon, 4096);
	munmap(zero, 4096);
	close(fd);
	return EXIT_SUCCESS;
}