【Linux】从零开始认识进程间通信 —— 管道

PIPE(2)                                                             Linux Programmer's Manual                                                            PIPE(2)

NAME
       pipe, pipe2 - create pipe

SYNOPSIS
       #include <unistd.h>

       /* On Alpha, IA-64, MIPS, SuperH, and SPARC/SPARC64; see NOTES */
       struct fd_pair {
           long fd[2];
       };
       struct fd_pair pipe();

       /* On all other architectures */
       int pipe(int pipefd[2]);

       #define _GNU_SOURCE             /* See feature_test_macros(7) */
       #include <fcntl.h>              /* Obtain O_* constant definitions */
       #include <unistd.h>

       int pipe2(int pipefd[2], int flags);

#include<iostream>
#include<unistd.h>
#include<cstring>
#include<sys/wait.h>
#include<cerrno>

using namespace std;

void SubProcessWrite(int wfd)
{
}
void FatherProcessRead(int rfd)
{
}
int main()
{
    //创建管道
    int pipefd[2];//[0] -> r | [1] -> w
    int n = pipe(pipefd);
    if(n != 0)
    {
        perror("创建管道错误!\n");
    }
    cout << "pipefd[0] : " << pipefd[0] << " pipefd[1] :" << pipefd[1] << endl;
    //创建子进程
    //关闭对应文件
    pid_t id = fork();
    if(id == 0)
    {
        //子进程 -- write
        close(pipefd[0]);

        SubProcessWrite(pipefd[1]);
        //使用完都关闭
        close(pipefd[1]);
        exit(0);
    }
    //父进程 -- read
    close(pipefd[1]);
    FatherProcessRead(pipefd[0]);
    //使用完都关闭
    close(pipefd[0]);
    pid_t rid = waitpid(id ,nullptr , 0 );
    if(rid > 0)
    {
        cout << "wait child process done!" << endl;
    }
    return 0;
}

#include<iostream>
#include<unistd.h>
#include<cstring>
#include<string>
#include<sys/wait.h>
#include<cerrno>

using namespace std;

string GetOtherMessage()
{
    static int cnt = 0;
    string messageid = to_string(cnt);
    cnt++;
    pid_t self_id = getpid();
    string stringid = std::to_string(self_id);

    string message = "messageid : ";
    message += messageid;
    message += "my pid :";
    message += stringid;

    return message;
}

void SubProcessWrite(int wfd)
{
    string messages = "father,I am your soon process !";
    while (true)
    {
        string info = messages + GetOtherMessage();
        //写入管道时没有写入'\0'，没有必要。在读取时添加
        write(wfd , info.c_str() , info.size());
        sleep(1);
    }
    
}
#define size 1024

void FatherProcessRead(int rfd)
{
    char inbuffer[size];
    while (true)
    {
    	//注意传入的参数 ， 读取 rfd 内的数据到inbuffer中,返回成功读取的个数。
        ssize_t n = read(rfd , inbuffer , sizeof(inbuffer) - 1);
        if( n > 0 ) 
        {
            inbuffer[n] = '\0';//添加'\0'
            cout << "father get message: " << inbuffer << endl;
        }

    }
}
int main()
{
    //创建管道
    int pipefd[2];//[0] -> r | [1] -> w
    int n = pipe(pipefd);
    if(n != 0)
    {
        perror("创建管道错误!\n");
    }
    cout << "pipefd[0] : " << pipefd[0] << " pipefd[1] :" << pipefd[1] << endl;
    sleep(1);
    //创建子进程
    //关闭对应文件
    pid_t id = fork();
    if(id == 0)
    {
        cout << "子进程关闭不需要的fd , 准备开始发消息" << endl;
        sleep(1);
        //子进程 -- write
        close(pipefd[0]);
        SubProcessWrite(pipefd[1]);
        //使用完都关闭
        close(pipefd[1]);
        exit(0);
    }
    cout << "子进程关闭不需要的fd , 准备开始接收消息" << endl;
    sleep(1);
    //父进程 -- read
    close(pipefd[1]);
    FatherProcessRead(pipefd[0]);
    //使用完都关闭
    close(pipefd[0]);
    pid_t rid = waitpid(id ,nullptr , 0 );
    if(rid > 0)
    {
        cout << "wait child process done!" << endl;
    }
    return 0;
}