1.\" $NetBSD: getdents.2,v 1.5 1999/12/02 21:42:36 kleink Exp $ 2.\" 3.\" Copyright (c) 1989, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)getdirentries.2 8.1 (Berkeley) 6/9/93 35.\" 36.Dd June 9, 1993 37.Dt GETDENTS 2 38.Os 39.Sh NAME 40.Nm getdents 41.Nd "get directory entries in a filesystem independent format" 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include <dirent.h> 46.Ft int 47.Fn getdents "int fd" "char *buf" "size_t nbytes" 48.Sh DESCRIPTION 49.Fn getdents 50reads directory entries from the directory 51referenced by the file descriptor 52.Fa fd 53into the buffer pointed to by 54.Fa buf , 55in a filesystem independent format. 56Up to 57.Fa nbytes 58of data will be transferred. 59.Fa nbytes 60must be greater than or equal to the 61block size associated with the file, 62see 63.Xr stat 2 . 64Some filesystems may not support 65.Fn getdents 66with buffers smaller than this size. 67.Pp 68The data in the buffer is a series of 69.Em dirent 70structures each containing the following entries: 71.Bd -literal -offset indent 72unsigned long d_fileno; 73unsigned short d_reclen; 74unsigned short d_namlen; 75char d_name[MAXNAMELEN + 1]; /* see below */ 76.Ed 77.Pp 78The 79.Fa d_fileno 80entry is a number which is unique for each 81distinct file in the filesystem. 82Files that are linked by hard links (see 83.Xr link 2 ) 84have the same 85.Fa d_fileno . 86The 87.Fa d_reclen 88entry is the length, in bytes, of the directory record. 89The 90.Fa d_name 91entry contains a null terminated file name. 92The 93.Fa d_namlen 94entry specifies the length of the file name excluding the null byte. 95Thus the actual size of 96.Fa d_name 97may vary from 1 to 98.Dv MAXNAMELEN 99\&+ 1. 100.Pp 101Entries may be separated by extra space. 102The 103.Fa d_reclen 104entry may be used as an offset from the start of a 105.Fa dirent 106structure to the next structure, if any. 107.Pp 108The actual number of bytes transferred is returned. 109The current position pointer associated with 110.Fa fd 111is set to point to the next block of entries. 112The pointer may not advance by the number of bytes returned by 113.Fn getdents . 114A value of zero is returned when 115the end of the directory has been reached. 116.Pp 117The current position pointer may be set and retrieved by 118.Xr lseek 2 . 119The current position pointer should only be set to a value returned by 120.Xr lseek 2 , 121or zero. 122.Sh RETURN VALUES 123If successful, the number of bytes actually transferred is returned. 124Otherwise, -1 is returned and the global variable 125.Va errno 126is set to indicate the error. 127.Sh ERRORS 128.Fn gtdents 129will fail if: 130.Bl -tag -width Er 131.It Bq Er EBADF 132.Fa fd 133is not a valid file descriptor open for reading. 134.It Bq Er EFAULT 135Either 136.Fa buf 137points outside the allocated address space. 138.It Bq Er EIO 139An 140.Tn I/O 141error occurred while reading from or writing to the file system. 142.It Bq Er EINVAL 143A directory was being read on NFS, but it was modified on the server while 144it was being read. 145.El 146.Sh SEE ALSO 147.Xr open 2 , 148.Xr lseek 2 149.Sh HISTORY 150The 151.Fn getdents 152function first appeared in 153.Nx 1.3 . 154