a0698341cd
It was reported that getdirentries(2) was returning dirents with d_off set to 0 for an NFS mount. This is believed to be correct behaviour at this time (it may change for some NFS mounts in the future), but is inconsistent with what the getdirentries(2) man page says. This patch fixes the man page. This is a content change. PR: 253428 Reviewed by: asomers MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D28664
209 lines
5.6 KiB
Groff
209 lines
5.6 KiB
Groff
.\" Copyright (c) 1989, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)getdirentries.2 8.2 (Berkeley) 5/3/95
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.\" $FreeBSD$
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.\"
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.Dd February 14, 2021
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.Dt GETDIRENTRIES 2
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.Os
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.Sh NAME
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.Nm getdirentries ,
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.Nm getdents
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.Nd "get directory entries in a file system independent format"
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/types.h
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.In dirent.h
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.Ft ssize_t
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.Fn getdirentries "int fd" "char *buf" "size_t nbytes" "off_t *basep"
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.Ft ssize_t
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.Fn getdents "int fd" "char *buf" "size_t nbytes"
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.Sh DESCRIPTION
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The
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.Fn getdirentries
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and
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.Fn getdents
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system calls read directory entries from the directory
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referenced by the file descriptor
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.Fa fd
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into the buffer pointed to by
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.Fa buf ,
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in a file system independent format.
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Up to
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.Fa nbytes
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of data will be transferred.
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The
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.Fa nbytes
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argument must be greater than or equal to the
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block size associated with the file,
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see
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.Xr stat 2 .
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Some file systems may not support these system calls
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with buffers smaller than this size.
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.Pp
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The data in the buffer is a series of
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.Vt dirent
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structures each containing the following entries:
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.Bd -literal -offset indent
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ino_t d_fileno;
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off_t d_off;
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uint16_t d_reclen;
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uint8_t d_type;
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uint16_t d_namlen;
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char d_name[MAXNAMLEN + 1]; /* see below */
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.Ed
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.Pp
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The
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.Fa d_fileno
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entry is a number which is unique for each
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distinct file in the file system.
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Files that are linked by hard links (see
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.Xr link 2 )
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have the same
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.Fa d_fileno .
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The
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.Fa d_off
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field returns a cookie which, if non-zero, can be used with
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.Xr lseek 2
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to position the directory descriptor to the next entry.
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The
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.Fa d_reclen
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entry is the length, in bytes, of the directory record.
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The
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.Fa d_type
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entry is the type of the file pointed to by the directory record.
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The file type values are defined in
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.Fa <sys/dirent.h> .
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The
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.Fa d_name
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entry contains a null terminated file name.
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The
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.Fa d_namlen
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entry specifies the length of the file name excluding the null byte.
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Thus the actual size of
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.Fa d_name
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may vary from 1 to
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.Dv MAXNAMLEN
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\&+ 1.
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.Pp
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Entries may be separated by extra space.
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The
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.Fa d_reclen
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entry may be used as an offset from the start of a
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.Fa dirent
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structure to the next structure, if any.
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.Pp
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The actual number of bytes transferred is returned.
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The current position pointer associated with
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.Fa fd
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is set to point to the next block of entries.
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The pointer may not advance by the number of bytes returned by
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.Fn getdirentries
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or
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.Fn getdents .
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A value of zero is returned when
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the end of the directory has been reached.
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.Pp
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If the
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.Fa basep
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pointer value is non-NULL ,
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the
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.Fn getdirentries
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system call writes the position of the block read into the location pointed to by
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.Fa basep .
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Alternatively, the current position pointer may be set and retrieved by
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.Xr lseek 2 .
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The current position pointer should only be set to a value returned by
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.Xr lseek 2 ,
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a value returned in the location pointed to by
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.Fa basep
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.Po Fn getdirentries
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only
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.Pc ,
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a value returned in the
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.Fa d_off
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field if it is non-zero,
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or zero.
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.Sh IMPLEMENTATION NOTES
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The
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.Fa d_off
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field is currently set to 0 by the NFS client, since the
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directory offset cookies returned by an NFS server cannot
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be used by
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.Xr lseek 2
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at this time.
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.Sh RETURN VALUES
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If successful, the number of bytes actually transferred is returned.
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Otherwise, -1 is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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The
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.Fn getdirentries
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system call
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa fd
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argument
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is not a valid file descriptor open for reading.
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.It Bq Er EFAULT
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Either
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.Fa buf
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or non-NULL
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.Fa basep
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point outside the allocated address space.
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.It Bq Er EINVAL
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The file referenced by
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.Fa fd
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is not a directory, or
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.Fa nbytes
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is too small for returning a directory entry or block of entries,
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or the current position pointer is invalid.
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.It Bq Er EIO
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An
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.Tn I/O
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error occurred while reading from or writing to the file system.
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.It Bq Er EINTEGRITY
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Corrupted data was detected while reading from the file system.
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.El
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.Sh SEE ALSO
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.Xr lseek 2 ,
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.Xr open 2
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.Sh HISTORY
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The
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.Fn getdirentries
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system call first appeared in
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.Bx 4.4 .
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The
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.Fn getdents
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system call first appeared in
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.Fx 3.0 .
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