GETDENTS(2) BSD System Calls Manual GETDENTS(2)
getdents -- get directory entries in a filesystem independent format
getdents(int fd, void *buf, size_t nbytes);
getdents() reads directory entries from the directory referenced by the
file descriptor fd into the buffer pointed to by buf, in a filesystem
independent format. Up to nbytes of data will be transferred. nbytes
must be greater than or equal to the block size associated with the file
(see stat(2)). Some filesystems may not support getdents() with buffers
smaller than this size.
The data in the buffer is a series of dirent structures each containing
at least the following entries:
char d_name[MAXNAMLEN + 1]; /* see below */
The d_fileno entry is a number which is unique for each distinct file in
the filesystem. Files that are linked by hard links (see link(2)) have
the same d_fileno. The d_off entry is the file offset of the next entry.
The d_reclen entry is the length, in bytes, of the directory record.
The d_type is the type of file, where the following are possible types:
DT_UNKNOWN, DT_FIFO, DT_CHR, DT_DIR, DT_BLK, DT_REG, DT_LNK, and DT_SOCK.
The d_namlen entry specifies the length of the file name excluding the
NUL byte. Thus the actual size of d_name may vary from 1 to MAXNAMLEN +
The d_name entry contains a NUL-terminated file name.
Entries may be separated by extra space. The d_reclen entry may be used
as an offset from the start of a dirent structure to the next structure,
Invalid entries with d_fileno set to 0 may be returned among regular
The actual number of bytes transferred is returned. The current position
pointer associated with fd is set to point to the next block of entries.
The pointer may not advance by the number of bytes returned by
The current position pointer may be set and retrieved by lseek(2). The
current position pointer should only be set to a value returned by
lseek(2), the value of d_off from an entry, or zero.
If successful, the number of bytes actually transferred is returned. A
value of zero is returned when the end of the directory has been reached.
Otherwise, -1 is returned and the global variable errno is set to indi-
cate the error.
getdents() will fail if:
[EBADF] fd is not a valid file descriptor open for reading.
[EFAULT] Part of buf points outside the process's allocated
[EINVAL] The file referenced by fd is not a directory, or
nbytes is too small for returning a directory entry or
block of entries, or the current position pointer is
[EIO] An I/O error occurred while reading from or writing to
the file system.
lseek(2), open(2), opendir(3), dirent(5)
The getdents() call is not a portable interface and should not be used
directly by applications. Use readdir(3) instead.
The getdirentries() function first appeared in 4.4BSD. In OpenBSD 5.5
the d_off entry was added to struct dirent and getdirentries() was
replaced with getdents().
BSD March 27, 2017 BSD