匿名管道和命名管道-编程知识

匿名管道和命名管道

管道是进程通信的一种方式。（进程通信需要让不同进程看到同一份资源）

管道分为匿名管道和命名管道两种。

管道只允许单向通信。

一.匿名管道

#include<iostream>
#include <unistd.h>
#include<cassert>
#include<cstring>
#include<errno.h>
#include<string>
#include <sys/types.h>
#include <sys/wait.h>//父写子读
int main()
{
//父进程创建管道int pipefd[2] = {0};int n = pipe(pipefd);assert(n == 0);(void*)n;std::cout << "pipefd[0]" << pipefd[0] << "pipefd[1]" << pipefd[1] << std::endl;//创建子进程pid_t id = fork();if(id < 0){perror("fork false\n");return 1;}if(id == 0) //子进程读{close(pipefd[1]); //关闭写//to dowhile(true){char ret[100];ssize_t n = read(pipefd[0], ret, sizeof(ret) - 1);if(n > 0){ret[n] = '\0';std::cout << "child read:" << ret << std::endl;}else if(n == 0)//代表read读不到内容时返回0{break;}}//关闭所有fdclose(pipefd[0]);exit(0);}//父进程close(pipefd[0]); //关闭读//to dostd::string s = "i am father";write(pipefd[1], s.c_str(), strlen(s.c_str()));sleep(5);//关闭所有fdclose(pipefd[1]);//回收子进程pid_t rid = waitpid(id, nullptr, 0);if(rid == id){std::cout << "wait success" << std::endl;}return 0;
}

二.命名管道

1.命令行创建命名管道

【】$ mkfifo filename

2.代码创建

A写B读

#include<iostream>
#include<cassert>
#include<cstring>
#include<errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>//A写  B读
int main()
{
//创建命名管道int n = mkfifo("fifo", 0666);if(n < 0){perror("mkfifo false\n");return 1;}int fd = open("fifo", O_WRONLY);if(fd < 0){perror("open fail\n");return 1;}//写入内容std::string ms = "i am process A";write(fd, ms.c_str(), ms.size());close(fd);return 0;
}

#include<iostream>
#include<cassert>
#include<cstring>
#include<errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>int main()
{int fd = open("fifo", O_RDONLY);if(fd < 0){perror("open fail\n");return 1;}
//读取内容char ret[1024];while(true){ssize_t n = read(fd, ret, sizeof(ret) - 1);if(n > 0){ret[n] = '\0';std::cout << "B read :" << ret << std::endl;}else if(n == 0){break;}}close(fd);return 0;
}