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

   1 /*============================================
  
   2   > Copyright (C) 2014 All rights reserved.
  
   3   > FileName：onepipe.c
  
   4   > author：donald
  
   5   > details：
  
   6 ==============================================*/
  
   7 #include <unistd.h>
  
   8 #include <stdio.h>
  
   9 #include <stdlib.h>
  
  10 #include <string.h>
  
  11 #define N 512
  
  12 int main(int argc, const char *argv[])
  
  13 {
  
  14     int pipefd[2];
  
  15    pid_t pid;
  
  16 
  
  17     if(pipe(pipefd) == -1){
  
  18         perror("pipe failed");
  
  19         exit(-1);
  
  20     }
  
  21     printf("%u\n",pid);
  
  22     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
  
  23     printf("%u\n",pid);
  
  24     if(0 == pid){
  
  25         close(pipefd[1]);//0 read 1 write
  
  26       //一个约定，父子进程都需遵守
  
  27 
  
  28         char buf[N];
  
  29         memset(buf,0,N);
  
  30         read(pipefd[0],buf,N);
  
  31         printf("child read:%s\n",buf);
  
  32 
  
  33         printf("child exit\n");
  
  34         exit(1);
  
  35     }else{
  
  36         close(pipefd[0]);//0 read
  
  37         char line[N];
  
  38         printf("parent begin\n");
  
  39 
  
  40         memset(line,0,N);
  
  41         fgets(line,N,stdin);
  
  42 
  
  43         write(pipefd[1],line,strlen(line));
  
  44         printf("parent exit\n");
  
  45         wait(NULL);//等待子进程的结束
  
  46     }
  
  47     return 0;
  
  48 }
  
  49         

   

• 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）：

  

   1 /*============================================
  
   2   > Copyright (C) 2014 All rights reserved.
  
   3   > FileName：my_pipe.c
  
   4   > author：donald
  
   5   > details：
  
   6 ==============================================*/
  
   7 #include <unistd.h>
  
   8 #include <stdio.h>
  
   9 #include <stdlib.h>
  
  10 #include <string.h>
  
  11 #define N 1024
  
  12 int main(int argc, const char *argv[])
  
  13 {
  
  14     int fds[2];
  
  15     if(pipe(fds) == -1){//只能有一对进行读写
  
  16         perror("failed");
  
  17         exit(1);
  
  18     }
  
  19     pid_t pid = fork();
  
  20     if(pid == -1){
  
  21         perror("error");
  
  22         exit(1);
  
  23     }
  
  24 
  
  25     while(1){
  
  26         if(pid == 0){//child read
  
  27             close(fds[1]);//1 write
  
  28             char buf[1024] = "";
  
  29             read(fds[0],buf,1024);//只能有一个读，
  
  30             printf("child read:%s\n",buf);
  
  31             //exit(1);
  
  32         }else{//parent write
  
  33 
  
  34             close(fds[0]);//0 read
  
  35             //        char *p = "hello,donald";
  
  36             char line[N];
  
  37           //  memset(line,0,N);
  
  38             fgets(line,N,stdin);
  
  39             write(fds[1],line,strlen(line));
  
  40             //wait(NULL);
  
  41         }
  
  42     }
  
  43     return 0;
  
  44 }

  View Code

  再贴上正确的方法：

   1 /*============================================
  
   2   > Copyright (C) 2014 All rights reserved.
  
   3   > FileName：twopipe.c
  
   4   > author：donald
  
   5   > details：
  
   6 ==============================================*/
  
   7 #include <unistd.h>
  
   8 #include <stdio.h>
  
   9 #include <stdlib.h>
  
  10 #include <string.h>
  
  11 #define N 512
  
  12 int main(int argc, const char *argv[])
  
  13 {
  
  14     int pipefd[2];
  
  15     pid_t pid;
  
  16     //pid = fork();
  
  17 
  
  18     if(pipe(pipefd) == -1){
  
  19         perror("pipe failed");
  
  20         exit(-1);
  
  21     }
  
  22     pid = fork();
  
  23     if(pid == 0){
  
  24         close(pipefd[1]);//0 read
  
  25             char buf[N];
  
  26         while(1){
  
  27             memset(buf,0,N);
  
  28             if(read(pipefd[0],buf,N) == 0){
  
  29                 break;
  
  30             }
  
  31             printf("child read:%s\n",buf);
  
  32         }
  
  33         printf("child exit\n");
  
  34         exit(1);
  
  35     }else{
  
  36         close(pipefd[0]);
  
  37         char line[N];
  
  38         while(memset(line,0,N),fgets(line,N,stdin) != NULL ){
  
  39             write(pipefd[1],line,strlen(line));
  
  40         }
  
  41         close(pipefd[1]);
  
  42         printf("parent exit\n");
  
  43         wait(NULL);
  
  44     }
  
  45     return 0;
  
  46 }