多进程通信之管道运用

/* pipe.c */
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#define MAX_DATA_LEN    256
#define DELAY_TIME    1

int main()
{
    pid_t pid;
    int pipe_fd[2];
    char buf[MAX_DATA_LEN];
    const char data[] = "Pipe Test Program";
    int real_read, real_write;
    
    memset((void*)buf, 0, sizeof(buf));
    if (pipe(pipe_fd) < 0) /* 创建管道 */
    {
        printf("pipe create error\n");
        exit(1);
    }
    if ((pid = fork()) == 0) /* 创建一子进程 */
    {
        /* 子进程关闭写描述符，并通过使子进程暂停1秒等待父进程已关闭相应的读描述符 */
        close(pipe_fd[1]);
        sleep(DELAY_TIME * 3);
        /* 子进程读取管道内容 */
        if ((real_read = read(pipe_fd[0], buf, MAX_DATA_LEN)) > 0)
        {
            printf("%d bytes read from the pipe is ‘%s‘\n", real_read, buf);
        }
        close(pipe_fd[0]); /* 关闭子进程读描述符 */
        exit(0);
    }
    else if (pid > 0)
    {
        /* 父进程关闭读描述符，并通过使父进程暂停1秒等待子进程已关闭相应的写描述符 */
        close(pipe_fd[0]);
        sleep(DELAY_TIME);
        if((real_write = write(pipe_fd[1], data, strlen(data))) !=  -1)
        {
            printf("Parent wrote %d bytes : ‘%s‘\n", real_write, data);
        }
        close(pipe_fd[1]); /*关闭父进程写描述符*/
        waitpid(pid, NULL, 0); /*收集子进程退出信息*/
        exit(0);
    }
}