Linux--无名管道

曾经终败给现在 2022-07-14 07:50 207阅读 0赞

#include "apue.h"
    //无名管道的读阻塞
    main(){
    	int fd[2];
    	int ret;
    	//初始化管道
    	ret=pipe(fd);
    	if(ret<0){
    		printf("fail to create pipe\n");
    		return -1;
    	}
    	printf("success to create pipe ret=%d fd[0]=%d fd[1]=%d\n",ret,fd[0],fd[1]);
    	char writebuf[128] = "hello nihao";
    	char readbuf[128];
    	//向管道写数据
    	write(fd[1],writebuf,sizeof(writebuf));
    	//向管道读数据
    	read(fd[0],readbuf,sizeof(readbuf));
    	printf("data of reading is buf=%s \n",readbuf);
    	
    	//清除数组保存的数据
    	memset(readbuf,0,sizeof(readbuf));
    	printf("after data was clear buf=%s \n",readbuf);
    	
    	//第二次从管道读取数据
    	read(fd[0],readbuf,sizeof(readbuf));//此时处于阻塞状态 查看进程为S状态  睡眠状态
    	printf("at second data of reading is buf=%s \n",readbuf);
    	
    	close(fd[0]);
    	close(fd[1]);
    	return 0;
    }

#include "apue.h"
    //无名管道的写阻塞
    main(){
    	int fd[2];
    	int ret;
    	//初始化管道
    	ret=pipe(fd);
    	if(ret<0){
    		printf("fail to create pipe\n");
    		return -1;
    	}
    	printf("success to create pipe ret=%d fd[0]=%d fd[1]=%d\n",ret,fd[0],fd[1]);
    	char writebuf[128] = "hellonihao";
    	char readbuf[128];
    	int max=0;
    	int tem=0;
    	//循环写数据 输出最大的写缓存是多少 65536
    	while(1){
    		//当写满缓存后开始阻塞
    		tem  = write(fd[1],writebuf,sizeof(writebuf));
    		max = max+tem;
    		printf("max writting buffer size is %d \n",max);
    	}
    	close(fd[0]);
    	close(fd[1]);
    	return 0;
    }

#include "apue.h"
    //无名管道的进程通信
    main(){
    	int fd[2];
    	int ret;
    	//初始化管道
    	ret=pipe(fd);
    	if(ret<0){
    		printf("fail to create pipe\n");
    		return -1;
    	}
    	printf("success to create pipe ret=%d fd[0]=%d fd[1]=%d\n",ret,fd[0],fd[1]);
    	
    	pid_t pid;
    	pid = fork();
    	if(pid==0){//子进程
    	sleep(5);
    	char readbuf[128];
    	//睡眠5秒后 等父进程关闭管道 然后向管道读数据 可以正常读取
    	read(fd[0],readbuf,sizeof(readbuf));
    	printf("between two processes data of reading is buf=%s \n",readbuf);
    	}
        if(pid>0){//父进程
    		char writebuf[128] = "hello nihao";
    		//向管道写数据
    	     write(fd[1],writebuf,sizeof(writebuf));
    	}
        
    	close(fd[0]);
    	close(fd[1]);
    	printf(" close pipe's proces is %d \n",pid);
    	return 0;
    }