1.\" $NetBSD: getdents.2,v 1.15 2004/05/13 10:20:58 wiz 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)getdirentries.2 8.1 (Berkeley) 6/9/93 31.\" 32.Dd June 9, 1993 33.Dt GETDENTS 2 34.Os 35.Sh NAME 36.Nm getdents 37.Nd "get directory entries in a filesystem independent format" 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In dirent.h 42.Ft int 43.Fn getdents "int fd" "char *buf" "size_t nbytes" 44.Sh DESCRIPTION 45.Fn getdents 46reads directory entries from the directory 47referenced by the file descriptor 48.Fa fd 49into the buffer pointed to by 50.Fa buf , 51in a filesystem independent format. 52Up to 53.Fa nbytes 54of data will be transferred. 55.Fa nbytes 56must be greater than or equal to the 57block size associated with the file, 58see 59.Xr stat 2 . 60Some filesystems may not support 61.Fn getdents 62with buffers smaller than this size. 63.Pp 64The data in the buffer is a series of 65.Em dirent 66structures each containing the following entries: 67.Bd -literal -offset indent 68u_int32_t d_fileno; 69u_int16_t d_reclen; 70u_int8_t d_type; 71u_int8_t d_namlen; 72char d_name[MAXNAMLEN + 1]; /* see below */ 73.Ed 74.Pp 75The 76.Fa d_fileno 77entry is a number which is unique for each 78distinct file in the filesystem. 79Files that are linked by hard links (see 80.Xr link 2 ) 81have the same 82.Fa d_fileno . 83If 84.Fa d_fileno 85is zero, the entry refers to a deleted file. 86.Pp 87The 88.Fa d_reclen 89entry is the length, in bytes, of the directory record. 90.Pp 91The 92.Fa d_type 93is the type of file, where the following are possible types: 94.Dv DT_UNKNOWN , 95.Dv DT_FIFO , 96.Dv DT_CHR , 97.Dv DT_DIR , 98.Dv DT_BLK , 99.Dv DT_REG , 100.Dv DT_LNK , 101.Dv DT_SOCK , 102and 103.Dv DT_WHT . 104.Pp 105The 106.Fa d_namlen 107entry specifies the length of the file name excluding the null byte. 108Thus the actual size of 109.Fa d_name 110may vary from 1 to 111.Dv MAXNAMLEN 112\&+ 1. 113.Pp 114The 115.Fa d_name 116entry contains a null terminated file name. 117.Pp 118Entries may be separated by extra space. 119The 120.Fa d_reclen 121entry may be used as an offset from the start of a 122.Fa dirent 123structure to the next structure, if any. 124.Pp 125The actual number of bytes transferred is returned. 126The current position pointer associated with 127.Fa fd 128is set to point to the next block of entries. 129The pointer may not advance by the number of bytes returned by 130.Fn getdents . 131A value of zero is returned when 132the end of the directory has been reached. 133.Pp 134The current position pointer may be set and retrieved by 135.Xr lseek 2 . 136The current position pointer should only be set to a value returned by 137.Xr lseek 2 , 138or zero. 139.Sh RETURN VALUES 140If successful, the number of bytes actually transferred is returned. 141Otherwise, \-1 is returned and the global variable 142.Va errno 143is set to indicate the error. 144.Sh ERRORS 145.Fn getdents 146will fail if: 147.Bl -tag -width Er 148.It Bq Er EBADF 149.Fa fd 150is not a valid file descriptor open for reading. 151.It Bq Er EFAULT 152Either 153.Fa buf 154points outside the allocated address space. 155.It Bq Er EIO 156An 157.Tn I/O 158error occurred while reading from or writing to the file system. 159.It Bq Er EINVAL 160A directory was being read on NFS, but it was modified on the server while 161it was being read. 162.El 163.Sh SEE ALSO 164.Xr lseek 2 , 165.Xr open 2 , 166.Xr dirent 5 167.Sh HISTORY 168The 169.Fn getdents 170function first appeared in 171.Nx 1.3 . 172