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方式1 使用mmap

#include <sys/mman.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <errno.h>#include <stdio.h>void perror(const char *s);void* create_shm(int size) {    int protection = PROT_READ | PROT_WRITE;    int visibility = MAP_ANONYMOUS | MAP_SHARED;    return mmap(NULL, size, protection, visibility, 0, 0);}int main() {    char* msg1 = "heheheheh";    char* msg2 = "xxxxoxoxoxox";    printf("size of msg2: %d\n", strlen(msg2));    void* shm = create_shm(12);    memcpy(shm, msg1, strlen(msg1));    int pid = fork();    if (pid < 0) {        perror("fork faild");    }    if (pid == 0) {        printf("entry child process...\n");        printf("child process read message from shared memory: %s\n", shm);        memcpy(shm, msg2, strlen(msg2));        printf("child process write message to shared memory: %s\n", msg2);    } else {        printf("this is parent process\n");        printf("parent process read message: %s\n", shm);        sleep(1);        printf("after 1 second parent process read: %s\n", shm);    }}

方法2 使用shmget

程序1 创建共享内存，并写入数据，程序2 获取共享内存，然后读取内容。

• 程序1

#include <sys/ipc.h>#include <sys/shm.h>#include <errno.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>// shmkey usually defined by ftok, 2222 here is jusk simplifyint shmkey = 2222;int main() {    // create shared memory    int shmid = shmget(shmkey, 1024, IPC_CREAT | 0777);    if (shmid < 0) {        perror("shmget faild");        exit(1);    }    // attach the shared memory    void* shm = shmat(shmid, NULL, 0);    char* message = "hello world";    printf("write message to shared message: %s\n", message);    memcpy(shm, message, strlen(message));    // wait another process to read shared memory    int wait = 30;    while (1) {        sleep(1);        wait--;        if (wait < 0) {            // delete shared memory and exit            printf("it's time to say good bye...\n");            shmctl(shmid, IPC_RMID, NULL);            return 0;        }    }}

• 程序2

#include <sys/ipc.h>#include <sys/shm.h>#include <errno.h>#include <stdio.h>#include <stdlib.h>// shmkey usually defined by ftok, 2222 here is jusk simplifyint shmkey = 2222;int main() {    // create shared memory    int shmid = shmget(shmkey, 1024, 0777);    if (shmid < 0) {        perror("shmget faild");        exit(1);    }    // attach the shared memory    void* shm = shmat(shmid, NULL, 0);    printf("read message to shared message: %s\n", shm);    shmdt(shm);}