【linux进程间通信(一)】匿名管道和命名管道

int main()
{
    //创建管道
    int pipefd[2]={0}; //0下标表示读取端,1下标表示写入端
    int n = pipe(pipefd);
    assert(n!=-1);
    (void)n;
#ifdef DEBUG//条件编译
    cout<<"[0]: "<<pipefd[0]<<" "<<"[1]: "<<pipefd[1]<<endl;
#endif
    //创建子进程
    pid_t id = fork();
    assert(id!=-1);
    if(id==0)//子进程, 构建单向通信
    {
        close(pipefd[1]);
        char buffer[1024];
        while(1)
        {
            ssize_t s = read(pipefd[0],buffer,sizeof(buffer)-1);
            if(s>0)
            {
                buffer[s]=0;
                cout<<"father# "<<buffer<<endl;
            }
            else//read的返回值等于0代表父进程的管道文件已经close了
            {
                cout<<"写入结束,子进程退出";
                break;
            }
        }
        exit(0);
    }
    //父进程写入,子进程读取
    close(pipefd[0]);
    string str = "我在给子进程发信息";
    int count=0;
    char send_buffer[1024];
    while(count<=5)
    {
        //构建一个变化的字符串
        snprintf(send_buffer, sizeof(send_buffer),"%s[%d]: %d",str.c_str(),getpid(),count++);//往缓冲区里写入数据
        //写入到管道中
        write(pipefd[1],send_buffer,sizeof(send_buffer));
        sleep(1);
    }
    close(pipefd[1]);
    pid_t ret = waitpid(id,NULL,0);
    assert(ret > 0);
    return 0;
}

#define SIZE 1024
#define MODE 0666
string ipcpath = "./fifo.ipc";
static void getmessage(int fd)
{
    //编写通信代码
    char buffer[SIZE];
    while(1)
    {
        memset(buffer,'\0',sizeof(buffer));
        ssize_t s = read(fd,buffer,sizeof(buffer)-1);
        if(s>0)//读取成功
        {
            cout<<"["<<getpid()<<"] "<<"client say: "<<buffer<<endl;
        }
        else if(s==0)//写端关闭,并且读到end
        {
            cerr<<"["<<getpid()<<"]"<<"read end"<<endl;
            break;
        }
        else//读取失败
        {
            perror("read");
            break;
        }
    }
}
int main()
{
    //创建管道文件
    int n = mkfifo(ipcpath.c_str(),MODE);
    if(n<0)
    {
        perror("mkfifo");
        exit(1);
    }
    //文件操作
    int fd = open(ipcpath.c_str(),O_RDONLY);//这里必须等待client进程将此管道文件打开后才能执行下面的代码
    if(fd<0)
    {
        perror("open");
        exit(2);
    }
    for(int i=0;i<4;i++)
    {
        int id = fork();
        if(id==0)
        {
            getmessage(fd);
            exit(0);
        }
    }
    
    close(fd);
    return 0;
}

#define SIZE 1024
#define MODE 0666
string ipcpath = "./fifo.ipc";
int main()
{
    //client不用自己创建管道文件,只需获取文件即可
    int fd = open(ipcpath.c_str(),O_WRONLY);
    if(fd<0)
    {
        perror("open");
        exit(1);
    }
    //通信过程
    string buffer;
    while(1)
    {
        cout<<"please Enter message: ";
        getline(cin,buffer);
        write(fd,buffer.c_str(),buffer.size());
    }
    close(fd);
    return 0;
}