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 }

     

posted @ 2014-08-22 02:22  donald_su  阅读(562)  评论(0)  编辑  收藏  举报