Linux命名管道FIFO实现进程间的文件传输

迷南。 2021-12-16 08:13 402阅读 0赞

设计两个程序，要求用命名管道FIFO，实现进程间的文件传输功能，即实现进程A将文件file1的内容复制给进程B。file1是已经存在的文件，file2可以不存在，如果存在就清空原来的内容。

接下来让我们了解一下有名管道的使用.

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我们先以一个简单的例子来熟悉FIFO的使用.

\#include <unistd.h>

\#include <stdlib.h>

\#include <fcntl.h>

\#include <limits.h>

\#include <sys/types.h>

\#include <sys/stat.h>

\#include <stdio.h>

\#include <string.h>

int main()

int pid;

int fd;

mkfifo("./named\_pipe", 0777);

pid = fork();

if(pid > 0)

fd = open("./named\_pipe", O\_WRONLY);

char buf\[20\] = "Hello world!";

write(fd, buf, strlen(buf) + 1);

close(fd);

else if(pid == 0)

fd = open("./named\_pipe", O\_RDONLY);

char buf2\[20\];

read(fd, buf2, 1024);

puts(buf2);

close(fd);

return 0;

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70 1][]

上面的程序实现了父子进程间通过有名管道的通信，但有名管道的存在就是为了挣脱在无名管道通信中的进程亲缘限制，所以接下来我们用两个程序文件来实现对无名管道的操作.

write.c:

\#include <unistd.h>

\#include <stdlib.h>

\#include <fcntl.h>

\#include <limits.h>

\#include <sys/types.h>

\#include <sys/stat.h>

\#include <stdio.h>

\#include <string.h>

int main()

int fd;

char buf\[20\] = "I am Kevin.";

mkfifo("./named\_pipe", 0777);

fd = open("./named\_pipe", O\_WRONLY);

write(fd, buf, strlen(buf) + 1);

close(fd);

return 0;

read.c:

\#include <unistd.h>

\#include <stdlib.h>

\#include <fcntl.h>

\#include <limits.h>

\#include <sys/types.h>

\#include <sys/stat.h>

\#include <stdio.h>

\#include <string.h>

int main()

int fd;

char buf\[20\];

fd = open("./named\_pipe", O\_RDONLY);

read(fd, buf, 1024);

close(fd);

puts(buf);

return 0;

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70 2][]

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将执行顺序改为先读后写，观察输出结果.

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70 4][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70 5][]

两种执行结果向我们展示了有名管道的自带阻塞功能，确实能为程序员对有名管道的读写操作带来极大的便利.

接下来，我将以个人对题目的理解，来实现题目的要求.

程序设计思路大概是这样的.先在当前目录下创建文件file，并向其写入一定量的信息；之后A程序创建FIFO，并将file文件内的信息读出，送入FIFO中.之后，B程序读FIFO中的信息，并将信息读出到内存，再创建文件file2，将这段信息写入file2.

A.c:

\#include <unistd.h>

\#include <stdlib.h>

\#include <fcntl.h>

\#include <limits.h>

\#include <sys/types.h>

\#include <sys/stat.h>

\#include <stdio.h>

\#include <string.h>

int main()

int fd;

char s\[150\];

mkfifo("./named\_FIFO", 0777);

FILE\* fp = fopen("./file", "r");

fgets(s, sizeof(s), fp);

fclose(fp);

fd = open("./named\_FIFO", O\_WRONLY);

write(fd, s, strlen(s) + 1);

close(fd);

return 0;

B.c:

\#include <unistd.h>

\#include <stdlib.h>

\#include <fcntl.h>

\#include <limits.h>

\#include <sys/types.h>

\#include <sys/stat.h>

\#include <stdio.h>

\#include <string.h>

int main()

int fd;

char s\[150\];

fd = open("./named\_FIFO",O\_RDONLY);

read(fd, s, 1024);

close(fd);

FILE\* fp = fopen("./file2", "w+");

fputs(s, fp);

fclose(fp);

return 0;

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70 6][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70 7][]

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从上面的运行过程中，我们可以看到，程序要求的功能已得到实现.

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