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 51212 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 write26       //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 read37         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 102412 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 read27             close(fds[1]);//1 write28             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 write33 34             close(fds[0]);//0 read35             //        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 51212 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 read25             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 }