使用mmap实现进程间通信

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#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;}

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