举几个C代码中使用shmsrc的例子

1. 下面是一个生产者和消费者使用共享内存进行通信的例子，其中使用了shmsrc来获取共享内存的数据：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/shm.h>

#define SHM_SIZE 1024

int main()
{
    key_t key = ftok(".", 's');
    int shmid = shmget(key, SHM_SIZE, IPC_CREAT | 0666);
    if (shmid == -1) {
        perror("shmget");
        exit(EXIT_FAILURE);
    }

    char *shmaddr = (char *) shmat(shmid, NULL, 0);
    if (shmaddr == (char *) -1) {
        perror("shmat");
        exit(EXIT_FAILURE);
    }

    char buf[SHM_SIZE];
    while (1) {
        // 生产者向共享内存写入数据
        printf("Enter a message: ");
        fgets(buf, SHM_SIZE, stdin);
        strncpy(shmaddr, buf, SHM_SIZE);

        // 消费者从共享内存读取数据
        printf("Received: %s", shmaddr);
    }

    if (shmdt(shmaddr) == -1) {
        perror("shmdt");
        exit(EXIT_FAILURE);
    }

    if (shmctl(shmid, IPC_RMID, 0) == -1) {
        perror("shmctl");
        exit(EXIT_FAILURE);
    }

    return 0;
}

2. 下面是一个父进程和子进程之间使用共享内存进行通信的例子，其中使用了shmsrc来获取共享内存的数据：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/shm.h>

#define SHM_SIZE 1024

int main()
{
    key_t key = ftok(".", 's');
    int shmid = shmget(key, SHM_SIZE, IPC_CREAT | 0666);
    if (shmid == -1) {
        perror("shmget");
        exit(EXIT_FAILURE);
    }

    pid_t pid = fork();
    if (pid == -1) {
        perror("fork");
        exit(EXIT_FAILURE);
    } else if (pid == 0) {
        char *shmaddr = (char *) shmat(shmid, NULL, 0);
        if (shmaddr == (char *) -1) {
            perror("shmat");
            exit(EXIT_FAILURE);
        }

        printf("Child process: %s", shmaddr);

        if (shmdt(shmaddr) == -1) {
            perror("shmdt");
            exit(EXIT_FAILURE);
        }

        exit(EXIT_SUCCESS);
    } else {
        char *shmaddr = (char *) shmat(shmid, NULL, 0);
        if (shmaddr == (char *) -1) {
            perror("shmat");
            exit(EXIT_FAILURE);
        }

        char buf[SHM_SIZE];
        printf("Enter a message: ");
        fgets(buf, SHM_SIZE, stdin);
        strncpy(shmaddr, buf, SHM_SIZE);

        if (shmdt(shmaddr) == -1) {
            perror("shmdt");
            exit(EXIT_FAILURE);
        }

        wait(NULL);

        if (shmctl(shmid, IPC_RMID, 0) == -1) {
            perror("shmctl");
            exit(EXIT_FAILURE);
        }

        return 0;
    }
}