GETDIRENTRIES(2)

NAME
getdirentries - get directory entries in a filesystem independent format

SYNOPSIS
#include <dirent.h>
int
getdirentries(int fd, char *buf, int nbytes, off_t *basep);

DESCRIPTION
getdirentries() 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 getdirentries() with buffers smaller than this size.

The data in the buffer is a series of dirent structures each containing the following entries:

    u_int32_t	d_fileno;
    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_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 getdirentries().

getdirentries() writes the position of the block read into the location pointed to by basep. Alternatively, 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), a value returned in the location pointed to by basep, or zero.

RETURN VALUES
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.

ERRORS
getdirentries() will fail if:

[EBADF]
    fd is not a valid file descriptor open for reading.

[EFAULT]
    Either buf or basep points outside the allocated address space.

[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 invalid.

[EIO]
    An I/O error occurred while reading from or writing to the file system.

SEE ALSO
lseek(2), open(2), opendir(3), dirent(5)

STANDARDS
The getdirentries() call is not a portable interface and should not be used directly by applications. Use readdir(3) instead.

HISTORY
The getdirentries() function first appeared in 4.4BSD.