1.\" $NetBSD: getdents.2,v 1.9 2002/02/08 01:28:17 ross 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 \*[Lt]dirent.h\*[Gt] 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[MAXNAMLEN + 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 . 86If 87.Fa d_fileno 88is zero, the entry refers to a deleted file. 89.Pp 90The 91.Fa d_reclen 92entry is the length, in bytes, of the directory record. 93.Pp 94The 95.Fa d_name 96entry contains a null terminated file name. 97.Pp 98The 99.Fa d_namlen 100entry specifies the length of the file name excluding the null byte. 101Thus the actual size of 102.Fa d_name 103may vary from 1 to 104.Dv MAXNAMLEN 105\&+ 1. 106.Pp 107Entries may be separated by extra space. 108The 109.Fa d_reclen 110entry may be used as an offset from the start of a 111.Fa dirent 112structure to the next structure, if any. 113.Pp 114The actual number of bytes transferred is returned. 115The current position pointer associated with 116.Fa fd 117is set to point to the next block of entries. 118The pointer may not advance by the number of bytes returned by 119.Fn getdents . 120A value of zero is returned when 121the end of the directory has been reached. 122.Pp 123The current position pointer may be set and retrieved by 124.Xr lseek 2 . 125The current position pointer should only be set to a value returned by 126.Xr lseek 2 , 127or zero. 128.Sh RETURN VALUES 129If successful, the number of bytes actually transferred is returned. 130Otherwise, -1 is returned and the global variable 131.Va errno 132is set to indicate the error. 133.Sh ERRORS 134.Fn getdents 135will fail if: 136.Bl -tag -width Er 137.It Bq Er EBADF 138.Fa fd 139is not a valid file descriptor open for reading. 140.It Bq Er EFAULT 141Either 142.Fa buf 143points outside the allocated address space. 144.It Bq Er EIO 145An 146.Tn I/O 147error occurred while reading from or writing to the file system. 148.It Bq Er EINVAL 149A directory was being read on NFS, but it was modified on the server while 150it was being read. 151.El 152.Sh SEE ALSO 153.Xr lseek 2 , 154.Xr open 2 155.Sh HISTORY 156The 157.Fn getdents 158function first appeared in 159.Nx 1.3 . 160