程序代码：

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

void read_pipe(int fd)
{
    char message[100];
    read(fd, message, 100);
    printf("read pipe message:%s", message);
}

void write_pipe(int fd)
{
    char *message = "Hello\n";
    write(fd, message, strlen(message) + 1);
}

int main()
{
    int fd[2];
    pid_t pid;
    int stat_val;
    if (pipe(fd))
    {
        printf("create pipe failed!\n");
    }
    pid = fork();
    switch (pid)
    {
    case -1:
        printf("fork error!\n");
        break;
    case 0:
        close(fd[1]);
        read_pipe(fd[0]);
        break;
    default:
        close(fd[0]);
        write_pipe(fd[1]);
        wait(&stat_val);
        break;
    }
    return 0;
}

程序代码：

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

int main()
{
    int fd1[2];
    int fd2[2];
    pid_t pid;
    int stat_val;
    char strMsg[20];
    char strMsgP2C[20]="Hello";
    char strMsgC2P[20]="hELLO";
    if (pipe(fd1))
    {
        printf("create pipe1 failed!\n");
    }
    if (pipe(fd2))
    {
        printf("create pipe1 failed!\n");
    }
    pid = fork();
    switch (pid)
    {
    case -1:        //    error
        printf("fork error!\n");
        break;
    case 0:            //    Child Process
        close(fd1[1]);
        close(fd2[0]);

        memset(strMsg,0,sizeof(strMsg));
        read(fd1[0],strMsg,sizeof(strMsg));
        printf("Child Process Get MSG: %s\n",strMsg);
        write(fd2[1],strMsgC2P,strlen(strMsgC2P));
        break;
    default:        //    Parent Process
        close(fd1[0]);
        close(fd2[1]);

        write(fd1[1],strMsgP2C,strlen(strMsgP2C));
        memset(strMsg,0,sizeof(strMsg));
        read(fd2[0],strMsg,sizeof(strMsg));
        printf("Parent Process Get MSG: %s\n",strMsg);
        wait(&stat_val);
        break;
    }
    return 0;
}