用c语言写出进程通信方式的程序

在C语言中，有两种常见的进程间通信（IPC，Inter-Process Communication）方式：管道（pipe）和消息队列（message queue）。这里分别给出两个简单示例：

1. **管道通信**：

#include <stdio.h>
#include <unistd.h>

#define BUFFER_SIZE 10

void parent(int pipe_fd) {
    char input[BUFFER_SIZE];
    printf("Parent: Please enter a message: ");
    fgets(input, sizeof(input), stdin);
    write(pipe_fd, input, strlen(input));
}

void child(int pipe_fd) {
    char received[BUFFER_SIZE];
    read(pipe_fd, received, BUFFER_SIZE);
    printf("Child: Parent said: %s", received);
}

int main() {
    int parent_pipe[2], child_pipe[2];
    if (pipe(parent_pipe) == -1 || pipe(child_pipe) == -1) {
        perror("Pipe creation failed");
        return 1;
    }

    pid_t pid = fork();
    if (pid == 0) { // Child process
        close(parent_pipe[0]); // Close unused end of parent's pipe
        child(child_pipe[1]);
        close(child_pipe[1]);
    } else { // Parent process
        close(child_pipe[1]); // Close unused end of child's pipe
        parent(parent_pipe[1]);
        close(parent_pipe[1]);
    }
    return 0;
}

在这个例子中，父进程通过`write`将消息写入管道，子进程通过`read`读取并显示。

2. **消息队列通信**：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mqueue.h>

mqd_t msg_queue;

void producer(char *msg) {
    struct msqid_ds mds;
    if (mq_open("/my_message_queue", O_CREAT | O_WRONLY, 0644, &mds) == -1) {
        perror("Message queue open failed");
        exit(1);
    }
    mq_send(msg_queue, msg, strlen(msg) + 1, 0); // Send message
    mq_close(msg_queue);
}

void consumer(void) {
    char buffer[100];
    struct msqid_ds mds;
    if (mq_open("/my_message_queue", O_RDONLY, 0, &mds) != 0) {
        perror("Message queue open failed");
        exit(1);
    }
    while (mq_receive(msg_queue, buffer, sizeof(buffer), NULL) > 0) {
        printf("Consumer: Received message: %s\n", buffer);
    }
    mq_close(msg_queue);
}

int main() {
    msg_queue = mq_open("/my_message_queue", O_CREAT | O_RDWR, 0644, NULL);
    if (msg_queue == NULL) {
        perror("Message queue creation failed");
        exit(1);
    }

    // Producer and consumer tasks can be separated here or run in parallel.
    // ...
    return 0;
}

这个示例展示了如何创建和使用消息队列，生产者往队列中发送消息，消费者从队列中接收并处理。