管道通訊之無名管道---pipe()

pipe()函數在子進程產生以前就應該存在。

• 父子進程之間只進行一次傳遞

   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();//這裏一個個大大的bug，本身的誤操做，debug了好久才搞定了
  23     printf("%u\n",pid);
  24     if(0 == pid){
  25         close(pipefd[1]);//0 read 1 write
  26       //一個約定，父子進程都需遵照
  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);//等待子進程的結束
  46     }
  47     return 0;
  48 }
  49         

   

• 父子進程經過管道，進行屢次讀寫操做，先貼上一個比較奇葩的方法（就是一個錯誤）：

   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){//只能有一對進行讀寫
  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);//只能有一個讀，
  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

  再貼上正確的方法：

   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 }