POSIX标准下文件描述符与文件流的转换操作代码

注意FILENO()和FDOPEN()函数的作用，输入参数与返回值。

 1 #include <sys/stat.h>
 2 #include <stdio.h>
 3 #include <stdlib.h>
 4 #include <fcntl.h>
 5 #include <unistd.h>
 6
 7 int main(void)
 8 {
 9     int fd;
10     FILE *stream;
11
12     printf("stdin is:\t%d\n", fileno(stdin));
13     printf("stdout is:\t%d\n", fileno(stdout));
14     printf("stderr is:\t%d\n",fileno(stderr));
15
16     unlink("test.txt");
17     fd = open("test.txt", O_CREAT | O_WRONLY, S_IREAD | S_IWRITE);
18     printf("fd file no is : %d\n",fd);
19     stream = fdopen(fd, "w");
20     if(stream == NULL)
21         printf("fdopen failed.\n");
22     else
23     {
24         fprintf(stream, "Hello World!\n");
25         fclose(stream);
26     }
27     printf("the content of the test.txt is : \n");
28     system("cat test.txt");
29     return 0;
30 }
31 ~

输出：

[root@localhost ccode]# ./fdopen_example
stdin is:       0
stdout is:      1
stderr is:      2
fd file no is : 3
the content of the test.txt is :
Hello World!