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.\"	@(#)getdirentries.2	8.1 (Berkeley) 6/9/93
.\"
.Dd June 4, 2010
.Dt GETDENTS 2
.Os
.Sh NAME
.Nm getdents
.Nd "get directory entries in a file system independent format"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In dirent.h
.Ft int
.Fn getdents "int fd" "char *buf" "size_t nbytes"
.Sh DESCRIPTION
.Fn getdents
reads directory entries from the directory
referenced by the file descriptor
.Fa fd
into the buffer pointed to by
.Fa buf ,
in a file system independent format.
Up to
.Fa nbytes
of data will be transferred.
.Fa nbytes
must be greater than or equal to the
block size associated with the file,
see
.Xr stat 2 .
Some file systems may not support
.Fn getdents
with buffers smaller than this size.
.Pp
The data in the buffer is a series of
.Em dirent
structures:
.Bd -literal -offset indent
struct dirent {
	ino_t	 d_fileno;		/* file number of entry */
	uint16_t d_reclen;		/* length of this record */
	uint16_t d_namlen;		/* length of d_name */
	uint8_t  d_type;		/* file type, see below */
	char	 d_name[MAXNAMLEN + 1];
};
.Ed
.Pp
The structure is described in
.Xr dirent 3 .
.Pp
Entries may be separated by extra space.
The
.Fa d_reclen
entry may be used as an offset from the start of a
.Fa dirent
structure to the next structure, if any.
.Pp
The actual number of bytes transferred is returned.
The current position pointer associated with
.Fa fd
is set to point to the next block of entries.
The pointer may not advance by the number of bytes returned by
.Fn getdents .
A value of zero is returned when
the end of the directory has been reached.
.Pp
The current position pointer may be set and retrieved by
.Xr lseek 2 .
The current position pointer should only be set to a value returned by
.Xr lseek 2 ,
or zero.
.Sh RETURN VALUES
If successful, the number of bytes actually transferred is returned.
Otherwise, \-1 is returned and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn getdents
will fail if:
.Bl -tag -width "[EINVAL]"
.It Bq Er EBADF
.Fa fd
is not a valid file descriptor open for reading.
.It Bq Er EFAULT
.Fa buf
points outside the allocated address space.
.It Bq Er EINVAL
A directory was being read on NFS, but it was modified on the server while
it was being read.
.It Bq Er EIO
An
.Tn I/O
error occurred while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr lseek 2 ,
.Xr open 2 ,
.Xr dirent 3
.Sh HISTORY
The
.Fn getdents
function first appeared in
.Nx 1.3 .