管道通信之无名管道---pipe()

pipe()函数在子进程产生之前就应该存在。

• 父子进程之间只进行一次传递

   /*============================================
     > Copyright (C) 2014 All rights reserved.
     > FileName：onepipe.c
     > author：donald
     > details：
   ==============================================*/
   #include <unistd.h>
   #include <stdio.h>
   #include <stdlib.h>
   #include <string.h>
   #define N 512
   int main(int argc, const char *argv[])
   {
       int pipefd[];
      pid_t pid;
  
       if(pipe(pipefd) == -){
           perror("pipe failed");
           exit(-);
       }
       printf("%u\n",pid);
       pid == fork();//这里一个个大大的bug，自己的误操作，debug了很久才搞定了
       printf("%u\n",pid);
       if( == pid){
           close(pipefd[]);//0 read 1 write
         //一个约定，父子进程都需遵守
  
           char buf[N];
           memset(buf,,N);
           read(pipefd[],buf,N);
           printf("child read:%s\n",buf);
  
           printf("child exit\n");
           exit();
       }else{
           close(pipefd[]);//0 read
           char line[N];
           printf("parent begin\n");
  
           memset(line,,N);
           fgets(line,N,stdin);
  
           write(pipefd[],line,strlen(line));
           printf("parent exit\n");
           wait(NULL);//等待子进程的结束
       }
       return ;
   }
           

• 父子进程通过管道，进行多次读写操作，先贴上一个比较奇葩的方法（就是一个错误）：

   /*============================================
     > Copyright (C) 2014 All rights reserved.
     > FileName：my_pipe.c
     > author：donald
     > details：
   ==============================================*/
   #include <unistd.h>
   #include <stdio.h>
   #include <stdlib.h>
   #include <string.h>
   #define N 1024
   int main(int argc, const char *argv[])
   {
       int fds[];
       if(pipe(fds) == -){//只能有一对进行读写
           perror("failed");
           exit();
       }
       pid_t pid = fork();
       if(pid == -){
           perror("error");
           exit();
       }
  
       while(){
           if(pid == ){//child read
               close(fds[]);//1 write
               char buf[] = "";
               read(fds[],buf,);//只能有一个读，
               printf("child read:%s\n",buf);
               //exit(1);
           }else{//parent write
  
               close(fds[]);//0 read
               //        char *p = "hello,donald";
               char line[N];
             //  memset(line,0,N);
               fgets(line,N,stdin);
               write(fds[],line,strlen(line));
               //wait(NULL);
           }
       }
       return ;
   }

  再贴上正确的方法：

   /*============================================
     > Copyright (C) 2014 All rights reserved.
     > FileName：twopipe.c
     > author：donald
     > details：
   ==============================================*/
   #include <unistd.h>
   #include <stdio.h>
   #include <stdlib.h>
   #include <string.h>
   #define N 512
   int main(int argc, const char *argv[])
   {
       int pipefd[];
       pid_t pid;
       //pid = fork();
  
       if(pipe(pipefd) == -){
           perror("pipe failed");
           exit(-);
       }
       pid = fork();
       if(pid == ){
           close(pipefd[]);//0 read
               char buf[N];
           while(){
               memset(buf,,N);
               if(read(pipefd[],buf,N) == ){
                   break;
               }
               printf("child read:%s\n",buf);
           }
           printf("child exit\n");
           exit();
       }else{
           close(pipefd[]);
           char line[N];
           while(memset(line,,N),fgets(line,N,stdin) != NULL ){
               write(pipefd[],line,strlen(line));
           }
           close(pipefd[]);
           printf("parent exit\n");
           wait(NULL);
       }
       return ;
   }