命名管道——进程通信案例

该案例是实现两个进程之间使用命名管道进行通信。

进程1：fifo01.c

 1 #include<unistd.h>
 2 #include<sys/types.h>
 3 #include<sys/stat.h>
 4 #include<stdio.h>
 5 #include<stdlib.h>
 6 #include<fcntl.h>
 7 #include<string.h>
 8 #include<errno.h>
 9 int main(int argc, char const *argv[])
10 {
11     if(mkfifo("myfifo1",0664) == -1)
12     {
13         if(errno != EEXIST)
14         {
15             perror("Fail to mkfifo1");
16             exit(1);
17         }
18     }
19     if(mkfifo("myfifo2",0664) == -1)
20     {
21         if(errno != EEXIST)
22         {
23             perror("Fail to mkfifo1");
24             exit(1);
25         }
26     }
27     int fd_w = open("myfifo1",O_WRONLY);
28     if(fd_w == -1)
29     {
30         perror("Fail to open myfifo1");
31         exit(1);
32     }
33     int fd_r = open("myfifo2",O_RDONLY);
34     if(fd_r == -1)
35     {
36         perror("Fail to open myfifo2");
37         exit(1);
38     }
39     pid_t pid;
40     pid = fork();
41     if(pid < 0)
42     {
43         perror("fail to fork");
44         exit(1);
45     }
46     else if(pid == 0)
47     {
48         while (1)
49         {
50             char buf[128] = "";
51             fgets(buf,sizeof(buf),stdin);
52             buf[strlen(buf) - 1] = '';
53             if(write(fd_w,buf,strlen(buf)) == -1)
54             {
55                 perror("Fail to write");
56                 exit(1);
57             }
58         }
59         
60     }
61     else
62     {
63         while(1)
64         {
65             char buf[128] = "";
66             if(read(fd_r,buf,sizeof(buf)) == -1)
67             {
68                 perror("fail to read");
69                 exit(1);
70             }
71             printf("receive from fifo02:%s
",buf);
72         }
73     }
74     close(fd_r);
75     close(fd_w);
76     return 0;
77 }

进程2：fifo02

 1 #include<unistd.h>
 2 #include<sys/types.h>
 3 #include<sys/stat.h>
 4 #include<stdio.h>
 5 #include<stdlib.h>
 6 #include<fcntl.h>
 7 #include<string.h>
 8 int main(int argc, char const *argv[])
 9 {
10     int fd_r = open("myfifo1",O_RDONLY);
11     if(fd_r == -1)
12     {
13         perror("fail to open");
14         exit(1);
15     }
16     int fd_w = open("myfifo2",O_WRONLY);
17     if(fd_w == -1)
18     {
19         perror("fail to write");
20         exit(1);
21     }
22     pid_t pid;
23     pid = fork();
24     if(pid == -1)
25     {
26         perror("fail to fork");
27         exit(1);
28     }
29     else if(pid == 0)
30     {
31         while (1)
32         {
33             char buf[128] = "";
34             if(read(fd_r,buf,sizeof(buf)) == -1)
35             {
36                 perror("fail to read");
37                 exit(1);
38             }
39             printf("received from fifo01:%s
",buf);
40         }
41         
42     }
43     else
44     {
45         while (1)
46         {
47             char buf[128] = "";
48             fgets(buf,sizeof(buf),stdin);
49             buf[strlen(buf) - 1] = '';
50             if(write(fd_w,buf,strlen(buf)) == -1)
51             {
52                 perror("fail to write");
53                 exit(1);
54             }
55         }
56         
57     }
58     
59     close(fd_w);
60     close(fd_r);
61     return 0;
62 }

运行结果：

原理如下：