以Ubuntu系统中的readdir函数为例。
一： #include <dirent.h>
(dp = opendir(argv[1])) = NULL
(dirp = readdir(dp)) != NULL
二：
在 /usr/include中， dirent.h。
#include <bits/dirent.h>
#ifndef __USE_FILE_OFFSET64
extern struct dirent *readdir (DIR *__dirp) __nonnull ((1));
#else
# ifdef __REDIRECT
extern struct dirent *__REDIRECT (readdir, (DIR *__dirp), readdir64)
__nonnull ((1));
# else
# define readdir readdir64
# endif
#endif
三：
在/usr/include/x86_64-linux-gun/bits中 ， dirent.h.
#ifndef _DIRENT_H
# error "Never use <bits/dirent.h> directly; include <dirent.h> instead."
#endif
struct dirent
{
#ifndef __USE_FILE_OFFSET64
__ino_t d_ino;
__off_t d_off;
#else
__ino64_t d_ino;
__off64_t d_off;
#endif
unsigned short int d_reclen;
unsigned char d_type;
char d_name[256]; /* We must not include limits.h! */
};