#include <unistd.h>
int pipe( int fildes[2] );  //出参，用于管道读写端的文件描述符；
返回值：0(成功)/-1(失败，错误信息在errno中)

2 读管道

#include <unistd.h>
ssize_t read( int fildes,      //入参，读端的文件描述符，fildes[0]
              void* buf,       //buf：出参，从管道读取的数据
              size_t nbyte );  //nbyte：入参，从管道读取的数据的额长度

返回值：>= 0 从管道中读取的数据的长度
       = -1 出错，错误信息在errno中

3 写管道

#include <unistd.h>
ssize_t write( int fildes,       //入参，写端的文件描述符，fildes[1]
               void* buf,        //buf：入参，需要写入管道的数据
               size_t nbyte );   //nbyte：入参，需要写入管带的数据的额长度

返回值：>= 0 写入管道的数据的长度
       = -1 出错，错误信息在errno中

/*************************************************************************
    > File Name: testpipe.c
    > Author: qiaozp
    > Mail: qiaozongpeng@163.com
    > Created Time: 2014-9-15 11:03:08
    > Step: 1 调用pipe函数在内核中创建一块存储区，
              存储区有一个读端(fildes[0]) 和 写端(fildes[1])
            2 调用fork函数创建子进程
            3 子进程负责写，关闭读端，写数据
            4 父进程负责读，关闭写端，读数据
 ************************************************************************/
#include <errno.h>
#include <iostream>
#include <unistd.h>
using namespace std;


int main()
{
    char buff[100] = {0};
    int pipeFd[2];
    //create pipe
    if (pipe(pipeFd) == -1)
    {
        cout << "pipe error." << endl;
        return -1;
    }

    int desPid = fork();
    if (desPid == 0)
    {
        cout << "son process for writing..." << endl;
        memset(buff, 0, sizeof(buff));
        strcat(buff, "hello");

        //close read, and write.
        close(pipeFd[0]);
        if (write(pipeFd[1], buff, sizeof(buff)) == -1)
        {
            cout << "son process failed to write pipe, errno is [" << errno << "]." <<  endl;
        }
        cout << "write data is : " << buff << endl;
        return 0;
    }
    else if (desPid > 0)
    {
        cout << "parent process for reading..." << endl;
        memset(buff, 0, sizeof(buff));

        //close write and read.
        close(pipeFd[1]);
        if (read(pipeFd[0], buff, sizeof(buff)) == -1)
        {
            cout << "parent process failed to read pipe, errno is [" << errno << "]." <<  endl;
        }
        cout << "read data is : " << buff << endl;
        return 0;
    }
    else
    {
        cout << "failed to create child process, please check. errno is [" << errno << "]." <<  endl;
        return -1;
    }

    return 0;
}