进程间通信——消息传递（管道）

来源：互联网发布：wait await java 编辑：程序博客网时间：2024/06/04 19:17

【申明：本文仅限于自我归纳总结和相互交流，有纰漏还望各位指出。联系邮箱：Mr_chenping@163.com】

本篇是IPC开篇吧，最近开始研读进程间通信，感知Linux博大精深啊，一步一步来吧。今天先说最原始的通信方式管道，管道分两种，无名管道pipe和有名管道fifo。本篇参考UNIX网络编程之进程间通信相关源码，首先我们来了解无名管道pipe。

无名管道特点：

一、半双工的，数据只能向一个方向流动，需要双方通信时，需要建立起两个管道。

二、只能用于父子进程或者兄弟进程之间（具有亲缘关系的进程）通信。

三、写入的内容每次都添加在管道缓冲区的末尾，并且每次都是从缓冲区的头部读出数据。

参考上图代码如下：

/*** 双向全双工管道。** 父：父进程把需要读取文件路径写入管道1,然后阻塞读取管道2,收到数据后打印出来** 子：读取管道1父进程写入管道的路劲,打开后读取文件内容写入管道2*/#include "../myipc.h"#define   MAXLINE   512void client(int readfd, int writefd){size_tlen;ssize_tn;charbuff[MAXLINE];/* 4read pathname */fgets(buff, MAXLINE, stdin);len = strlen(buff);/* fgets() guarantees null byte at end */if (buff[len-1] == '\n')len--;/* delete newline from fgets() *//* 4write pathname to IPC channel */write(writefd, buff, len);/* 4read from IPC, write to standard output */while ( (n = read(readfd, buff, MAXLINE)) > 0){printf("Now read the path file data is :\n");write(STDOUT_FILENO, buff, n);}}void server(int readfd, int writefd){intfd;ssize_tn;charbuff[MAXLINE+1];/* 4read pathname from IPC channel */if ( (n = read(readfd, buff, MAXLINE)) == 0)//err_quit("end-of-file while reading pathname");perror("end-of-file while reading pathname");buff[n] = '\0';/* null terminate pathname */if ( (fd = open(buff, O_RDONLY)) < 0) {/* 4error: must tell client */snprintf(buff + n, sizeof(buff) - n, ": can't open, %s\n", strerror(errno));n = strlen(buff);write(writefd, buff, n);} else {/* 4open succeeded: copy file to IPC channel */while ( (n = read(fd, buff, MAXLINE)) > 0)write(writefd, buff, n);close(fd);}}int main(int argc, char **argv){intpipe1[2], pipe2[2];pid_tchildpid;pipe(pipe1);/* create two pipes */pipe(pipe2);if ( (childpid = fork()) == 0) {/* child */close(pipe1[1]);close(pipe2[0]);server(pipe1[0], pipe2[1]);exit(0);}/* 4parent */close(pipe1[0]);close(pipe2[1]);client(pipe2[0], pipe1[1]);waitpid(childpid, NULL, 0);/* wait for child to terminate */exit(0);}