使用mmap实现进程间通信

#include <sys/types.h>
#include <sys/mman.h>
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

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;
}