10.3 进程间通信--管道

  1 #include <unistd.h>
  2 #include <sys/stat.h>
  3 #include <sys/wait.h>
  4 #include <sys/types.h>
  5 #include <fcntl.h>
  6 
  7 #include <stdlib.h>
  8 #include <stdio.h>
  9 #include <errno.h>
 10 #include <string.h>
 11 #include <signal.h>
 12 
 13 #define ERR_EXIT(m)  14     do  15     {  16         perror(m);  17         exit(EXIT_FAILURE);  18     } while(0)
 19 
 20 
 21 //测试 默认情况下，管道的读写
 22 int main41(void )
 23 {
 24     int pipefd[2];
 25     pid_t pid;
 26     if (pipe(pipefd) == -1 )    
 27     {
 28         printf("pipe() err..\n");    
 29         return -1;
 30     }
 31     pid = fork();
 32     if (pid == -1)
 33     {
 34         printf("fork err..\n");
 35         return -1;
 36     }
 37     
 38     if (pid == 0)
 39     {
 40         printf("子进程延迟3秒后，再写。。\n");
 41         sleep(3);
 42         close(pipefd[0]);
 43         write(pipefd[1], "hello hello....", 6);
 44         close(pipefd[1]);
 45         printf("child .....quit\n");
 46         exit(0);
 47     } 
 48     else if (pid > 0 )
 49     {
 50         int len = 0; 
 51         char buf[100] = {0};
 52         close(pipefd[1]);
 53     
 54     
 55         printf("测试非阻塞情况下，begin read ...\n");
 56         len = -1;
 57         while (len < 0)
 58         {
 59                 len = read(pipefd[0], buf, 100);
 60                 if (len == -1)
 61                 {
 62                     sleep(1);
 63                     //close(pipefd[0]);
 64                     perror("\nread err:");
 65                     //exit(0);
 66                 }
 67         }
 68     
 69         printf("len:%d, buf:%s \n", len , buf);
 70         close(pipefd[0]);
 71     }
 72 
 73     wait(NULL);
 74     printf("parent ..quit\n");
 75     return 0;
 76 
 77 }
 78 
 79 
 80 //文件状态设置成阻塞非阻塞
 81 int main(void )
 82 {
 83     int pipefd[2];
 84     pid_t pid;
 85     if (pipe(pipefd) == -1 )    
 86     {
 87         printf("pipe() err..\n");    
 88         return -1;
 89     }
 90     pid = fork();
 91     if (pid == -1)
 92     {
 93         printf("fork err..\n");
 94         return -1;
 95     }
 96     
 97     if (pid == 0)
 98     {
 99         sleep(3);
100         close(pipefd[0]);
101         write(pipefd[1], "hello hello....", 6);
102         close(pipefd[1]);
103         printf("child .....quit\n");
104     } 
105     else if (pid > 0 )
106     {
107         int len = 0; 
108         char buf[100] = {0};
109         close(pipefd[1]);
110     
111     /*    
112        int fcntl(int fd, int cmd);
113        int fcntl(int fd, int cmd, long arg);
114        int fcntl(int fd, int cmd, struct flock *lock);
115 F_GETFL  F_SETFL O_NONBLOCK
116 //注意不要设置错误成F_GETFD  F_SETFD
117 
118 
119 */
120         int flags = fcntl(pipefd[0], F_GETFL);
121         flags = flags | O_NONBLOCK;
122         int ret = fcntl(pipefd[0], F_SETFL, flags);
123         if (ret == -1)
124         {
125             printf("fcntl err.\n");
126             exit(0);
127         }
128         
129         //把pipefd[0]文件描述符修改成非阻塞 man fcntl
130         printf("begin read ...\n");
131         len = -1;
132         while (len < 0)
133         {
134                 len = read(pipefd[0], buf, 100);
135                 if (len == -1)
136                 {
137                     sleep(1);
138                     //close(pipefd[0]);
139                     perror("read err.\n");
140                     //exit(0);
141                 }
142         }
143     
144         printf("len:%d, buf:%s \n", len , buf);
145         close(pipefd[0]);
146     }
147 
148     wait(NULL);
149     printf("parent ..quit\n");
150     return 0;
151 
152 }