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.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
.\"
.\" %%%LICENSE_START(BSD_4_CLAUSE_UCB)
.\" 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.
.\" %%%LICENSE_END
.\"
.\" @(#)fseek.3 6.11 (Berkeley) 6/29/91
.\"
.\" Converted for Linux, Mon Nov 29 15:22:01 1993, faith@cs.unc.edu
.\"
.TH FSEEK 3 2014-05-28 "GNU" "Linux Programmer's Manual"
.SH NAME
fgetpos, fseek, fsetpos, ftell, rewind \- reposition a stream
.SH SYNOPSIS
.B #include <stdio.h>
.sp
.BI "int fseek(FILE *" stream ", long " offset ", int " whence );
.BI "long ftell(FILE *" stream );
.BI "void rewind(FILE *" stream );
.BI "int fgetpos(FILE *" stream ", fpos_t *" pos );
.br
.BI "int fsetpos(FILE *" stream ", const fpos_t *" pos );
.SH DESCRIPTION
The
.BR fseek ()
function sets the file position indicator for the stream pointed to by
.IR stream .
The new position, measured in bytes, is obtained by adding
.I offset
bytes to the position specified by
.IR whence .
If
.I whence
is set to
.BR SEEK_SET ,
.BR SEEK_CUR ,
or
.BR SEEK_END ,
the offset is relative to the start of the file, the current position
indicator, or end-of-file, respectively.
A successful call to the
.BR fseek ()
function clears the end-of-file indicator for the stream and undoes
any effects of the
.BR ungetc (3)
function on the same stream.
.PP
The
.BR ftell ()
function obtains the current value of the file position indicator for the
stream pointed to by
.IR stream .
.PP
The
.BR rewind ()
function sets the file position indicator for the stream pointed to by
.I stream
to the beginning of the file.
It is equivalent to:
.PP
.RS
(void) fseek(stream, 0L, SEEK_SET)
.RE
.PP
except that the error indicator for the stream is also cleared (see
.BR clearerr (3)).
.PP
The
.BR fgetpos ()
and
.BR fsetpos ()
functions are alternate interfaces equivalent to
.BR ftell ()
and
.BR fseek ()
(with
.I whence
set to
.BR SEEK_SET ),
setting and storing the current value of the file offset into or from the
object referenced by
.IR pos .
On some non-UNIX systems, an
.I fpos_t
object may be a complex object and these routines may be the only way to
portably reposition a text stream.
.SH RETURN VALUE
The
.BR rewind ()
function returns no value.
Upon successful completion,
.BR fgetpos (),
.BR fseek (),
.BR fsetpos ()
return 0,
and
.BR ftell ()
returns the current offset.
Otherwise, \-1 is returned and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EBADF
The
.I stream
specified is not a seekable stream.
.TP
.B EINVAL
The
.I whence
argument to
.BR fseek ()
was not
.BR SEEK_SET ,
.BR SEEK_END ,
or
.BR SEEK_CUR .
Or: the resulting file offset would be negative.
.PP
The functions
.BR fgetpos (),
.BR fseek (),
.BR fsetpos (),
and
.BR ftell ()
may also fail and set
.I errno
for any of the errors specified for the routines
.BR fflush (3),
.BR fstat (2),
.BR lseek (2),
and
.BR malloc (3).
.SH CONFORMING TO
C89, C99.
.SH SEE ALSO
.BR lseek (2),
.BR fseeko (3)
.SH COLOPHON
This page is part of release 3.74 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%http://www.kernel.org/doc/man\-pages/.
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