211 lines
5.6 KiB
Groff
211 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 April 11, 2022
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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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.It Bq Er ENOENT
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Directory unlinked but still open.
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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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