Linux使用mmap实现父子进程间的通信

void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset);

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

#define SHM_SIZE 1024

int main() {
    // 使用mmap创建匿名映射
    void *shared_mem = mmap(NULL, SHM_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
    if (shared_mem == MAP_FAILED) {
        perror("mmap failed");
        exit(EXIT_FAILURE);
    }

    pid_t pid = fork();
    
    if (pid < 0) {
        perror("fork failed");
        exit(EXIT_FAILURE);
    } else if (pid == 0) {
        // 子进程代码
        printf("Child process writing to shared memory\n");
        strcpy((char *)shared_mem, "Hello from child process!");
        
        // 子进程结束
        exit(EXIT_SUCCESS);
    } else {
        // 父进程代码
        // 等待子进程结束
        wait(NULL);
        
        printf("Parent process reading from shared memory: %s\n", (char *)shared_mem);
        
        // 解除映射
        if (munmap(shared_mem, SHM_SIZE) == -1) {
            perror("munmap failed");
            exit(EXIT_FAILURE);
        }
    }
    
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <semaphore.h>

#define SHM_SIZE 1024
#define SEM_NAME "/my_semaphore"

typedef struct {
    char message[SHM_SIZE];
    int ready;
} SharedData;

int main() {
    // 创建或打开信号量
    sem_t *sem = sem_open(SEM_NAME, O_CREAT, 0644, 0);
    if (sem == SEM_FAILED) {
        perror("sem_open failed");
        exit(EXIT_FAILURE);
    }
    
    // 使用mmap创建匿名映射
    SharedData *shared_data = mmap(NULL, sizeof(SharedData), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
    if (shared_data == MAP_FAILED) {
        perror("mmap failed");
        exit(EXIT_FAILURE);
    }
    
    pid_t pid = fork();
    
    if (pid < 0) {
        perror("fork failed");
        exit(EXIT_FAILURE);
    } else if (pid == 0) {
        // 子进程代码
        printf("Child process writing to shared memory\n");
        strcpy(shared_data->message, "Hello from child process with synchronization!");
        shared_data->ready = 1;
        
        // 通知父数据已准备好
        if (sem_post(sem) == -1) {
            perror("sem_post failed");
            exit(EXIT_FAILURE);
        }
        
        // 子进程结束
        exit(EXIT_SUCCESS);
    } else {
        // 父进程代码
        // 等待子进程通知
        if (sem_wait(sem) == -1) {
            perror("sem_wait failed");
            exit(EXIT_FAILURE);
        }
        
        printf("Parent process reading from shared memory: %s\n", shared_data->message);
        
        // 解除映射
        if (munmap(shared_data, sizeof(SharedData)) == -1) {
            perror("munmap failed");
            exit(EXIT_FAILURE);
        }
        
        // 关闭并删除信号量
        if (sem_close(sem) == -1) {
            perror("sem_close failed");
            exit(EXIT_FAILURE);
        }
        
        if (sem_unlink(SEM_NAME) == -1) {
            perror("sem_unlink failed");
            exit(EXIT_FAILURE);
        }
    }
    
    return 0;
}