1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
142 lines
3.9 KiB
Groff
142 lines
3.9 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)lseek.2 8.3 (Berkeley) 4/19/94
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd April 19, 1994
|
|
.Dt LSEEK 2
|
|
.Os BSD 4
|
|
.Sh NAME
|
|
.Nm lseek
|
|
.Nd reposition read/write file offset
|
|
.Sh SYNOPSIS
|
|
.Fd #include <unistd.h>
|
|
.Ft off_t
|
|
.Fn lseek "int fildes" "off_t offset" "int whence"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn lseek
|
|
function repositions the offset of the file descriptor
|
|
.Fa fildes
|
|
to the
|
|
argument
|
|
.Fa offset
|
|
according to the directive
|
|
.Fa whence.
|
|
The argument
|
|
.Fa fildes
|
|
must be an open
|
|
file descriptor.
|
|
.Fn Lseek
|
|
repositions the file position pointer associated with the file
|
|
descriptor
|
|
.Fa fildes
|
|
as follows:
|
|
.Bl -item -offset indent
|
|
.It
|
|
If
|
|
.Fa whence
|
|
is
|
|
.Dv SEEK_SET ,
|
|
the offset is set to
|
|
.Fa offset
|
|
bytes.
|
|
.It
|
|
If
|
|
.Fa whence
|
|
is
|
|
.Dv SEEK_CUR ,
|
|
the offset is set to its current location plus
|
|
.Fa offset
|
|
bytes.
|
|
.It
|
|
If
|
|
.Fa whence
|
|
is
|
|
.Dv SEEK_END ,
|
|
the offset is set to the size of the
|
|
file plus
|
|
.Fa offset
|
|
bytes.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn lseek
|
|
function allows the file offset to be set beyond the end
|
|
of the existing end-of-file of the file. If data is later written
|
|
at this point, subsequent reads of the data in the gap return
|
|
bytes of zeros (until data is actually written into the gap).
|
|
.Pp
|
|
Some devices are incapable of seeking. The value of the pointer
|
|
associated with such a device is undefined.
|
|
.Sh RETURN VALUES
|
|
Upon successful completion,
|
|
.Fn lseek
|
|
returns the resulting offset location as measured in bytes from the
|
|
beginning of the file.
|
|
Otherwise,
|
|
a value of -1 is returned and
|
|
.Va errno
|
|
is set to indicate
|
|
the error.
|
|
.Sh ERRORS
|
|
.Fn Lseek
|
|
will fail and the file position pointer will remain unchanged if:
|
|
.Bl -tag -width [EINVAL]
|
|
.It Bq Er EBADF
|
|
.Em Fildes
|
|
is not an open file descriptor.
|
|
.It Bq Er ESPIPE
|
|
.Em Fildes
|
|
is associated with a pipe, socket, or FIFO.
|
|
.It Bq Er EINVAL
|
|
.Fa Whence
|
|
is not a proper value.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr dup 2 ,
|
|
.Xr open 2
|
|
.Sh BUGS
|
|
This document's use of
|
|
.Fa whence
|
|
is incorrect English, but is maintained for historical reasons.
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn lseek
|
|
function call is expected to conform to
|
|
.St -p1003.1-90 .
|
|
.Sh HISTORY
|
|
A
|
|
.Fn lseek
|
|
function call appeared in
|
|
.At v7 .
|