'\" te
.\" Copyright (c) 2005, Sun Microsystems, Inc.  All Rights Reserved.
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
.\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE.  If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
.TH LLSEEK 2 "Apr 1, 2005"
.SH NAME
llseek \- move extended read/write file pointer
.SH SYNOPSIS
.LP
.nf
#include <sys/types.h>
#include <unistd.h>

\fBoffset_t\fR \fBllseek\fR(\fBint\fR \fIfildes\fR, \fBoffset_t\fR \fIoffset\fR, \fBint\fR \fIwhence\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBllseek()\fR function sets the 64-bit extended file pointer associated
with the open file descriptor specified by \fIfildes\fR as follows:
.RS +4
.TP
.ie t \(bu
.el o
If \fIwhence\fR is \fBSEEK_SET\fR, the pointer is set to \fIoffset\fR bytes.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If \fIwhence\fR is \fBSEEK_CUR\fR, the pointer is set to its current location
plus \fIoffset\fR.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If \fIwhence\fR is \fBSEEK_END\fR, the pointer is set to the size of the file
plus \fIoffset\fR.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If \fIwhence\fR is \fBSEEK_HOLE\fR, the offset of the start of the next hole
greater than or equal to the supplied offset is returned. The definition of a
hole immediately follows this list.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If \fIwhence\fR is \fBSEEK_DATA\fR, the file pointer is set to the start of the
next non-hole file region greater than or equal to the supplied offset.
.RE
.sp
.LP
A "hole" is defined as a contiguous range of bytes in a file, all having the
value of zero, but not all zeros in a file are guaranteed to be represented as
holes returned with \fBSEEK_HOLE\fR. Filesystems are allowed to expose ranges
of zeros with \fBSEEK_HOLE\fR, but not required to. Applications can use
\fBSEEK_HOLE\fR to optimise their behavior for ranges of zeros, but must not
depend on it to find all such ranges in a file. The existence of a hole at the
end of every data region allows for easy programming and implies that a virtual
hole exists at the end of the file.
.sp
.LP
For filesystems that do not supply information about holes, the file will be
represented as one entire data region.
.sp
.LP
Although each file has a 64-bit file pointer associated with it, some existing
file system types (such as \fBtmpfs\fR) do not support the full range of 64-bit
offsets.  In particular, on such file systems, non-device files remain limited
to offsets of less than two gigabytes.  Device drivers may support offsets of
up to 1024 gigabytes for device special files.
.sp
.LP
Some devices are incapable of seeking. The value of the file pointer associated
with such a device is undefined.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBllseek()\fR returns the resulting pointer
location as measured in bytes from the beginning of the file. Remote file
descriptors are the only ones that allow negative file pointers. Otherwise,
\fB\(mi1\fR is returned, the file pointer remains unchanged, and \fBerrno\fR is
set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBllseek()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEBADF\fR\fR
.ad
.RS 10n
The \fIfildes\fR argument is not an open file descriptor.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The \fIwhence\fR argument is not \fBSEEK_SET\fR, \fBSEEK_CUR\fR, or
\fBSEEK_END\fR; the \fIoffset\fR argument is not a valid offset for this file
system type; or the \fIfildes\fR argument is not a remote file descriptor and
the resulting file pointer would be negative.
.RE

.sp
.ne 2
.na
\fB\fBENXIO\fR\fR
.ad
.RS 10n
For \fBSEEK_DATA\fR, there are no more data regions past the supplied offset.
For \fBSEEK_HOLE\fR, there are no more holes past the supplied offset.
.RE

.sp
.ne 2
.na
\fB\fBESPIPE\fR\fR
.ad
.RS 10n
The \fIfildes\fR argument is associated with a pipe or FIFO.
.RE

.SH SEE ALSO
.sp
.LP
\fBcreat\fR(2), \fBdup\fR(2), \fBfcntl\fR(2), \fBlseek\fR(2), \fBopen\fR(2)