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GETDENTS(2) System Calls Manual GETDENTS(2)

getdentsget directory entries in a filesystem independent format

#include <dirent.h>

getdents(int fd, void *buf, size_t nbytes);

() 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 structures each containing at least the following entries:

ino_t		d_fileno;
off_t		d_off;
u_int16_t	d_reclen;
u_int8_t	d_type;
u_int8_t	d_namlen;
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 + 1.

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, if any.

Invalid entries with d_fileno set to 0 may be returned among regular entries.

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 indicate the error.

getdents() will fail if:

fd is not a valid file descriptor open for reading.
Part of buf points outside the process's allocated address space.
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 invalid.
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().

December 16, 2014 OpenBSD-5.9