GETDIRENTRIES(2)

NAME
getdirentries, getdents - get directory entries in a filesystem independent format

LIBRARY
libc

SYNOPSIS
#include <sys/types.h>
#include <dirent.h>
int
getdirentries(int fd, char *buf, int nbytes, long *basep);
int
getdents(int fd, char *buf, int nbytes);
size_t
_DIRENT_DIRSIZ(struct dirent *dp);
struct dirent *
_DIRENT_NEXT(struct dirent *dp);

DESCRIPTION
The getdirentries() and getdents() functions read 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. The nbytes argument must be greater than or equal to the block size associated with the file, see stat(2). Some filesystems may not support these functions with buffers smaller than this size.

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

    ino_t     d_fileno;
    u_int8_t  d_type;
    u_int8_t  d_namlen;
    char      d_name[...];	/* 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_type entry is the type of the file pointed to by the directory record. The file type values are defined in <sys/dirent.h>. The d_name entry contains a null terminated file name. The d_namlen entry specifies the length of the file name excluding the null byte. Thus the actual size of d_name may vary from 1 to MAXNAMELEN + 1.

Entries may be separated by extra space. To get the total size of a dirent structure, use the _DIRENT_DIRSIZ macro, or use _DIRENT_NEXT to get a pointer to the following dirent structure.

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() or getdents(). A value of zero is returned when the end of the directory has been reached.

The getdirentries() function 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 (getdirentries() only) or zero.

RETURN VALUES
If successful, the number of bytes actually transferred is returned. 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 point 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)

HISTORY
The getdirentries() function first appeared in 4.4BSD. The getdents() function first appeared in FreeBSD 3.0.

BUGS
Unfortunately, *basep is only 32 bits wide on 32 bit platforms and may not be wide enough to accommodate the directory position cookie. Modern users should use lseek(2). to retrieve and set the seek position within the directory. The seek offset is 64 bits wide on all platforms.