opendir()是一个打开目录的函数,它的参数可以是一个目录的名字,比如.、..、User等等。它的返回值是一个 DIR结构体指针。 DIR 结构体的定义为:
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typedefstruct { int __dd_fd; /* file descriptor associated with directory */ long __dd_loc; /* offset in current buffer */ long __dd_size; /* amount of data returned */ char *__dd_buf; /* data buffer */ int __dd_len; /* size of data buffer */ long __dd_seek; /* magic cookie returned */ __unused long __padding; /* (__dd_rewind space left for bincompat) */ int __dd_flags; /* flags for readdir */ __darwin_pthread_mutex_t __dd_lock; /* for thread locking */ struct _telldir *__dd_td;/* telldir position recording */ } DIR;