FSETPOS(3P) POSIX Programmer's Manual FSETPOS(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAMEfsetpos — set current file position
int fsetpos(FILE *stream, const fpos_t *pos);
The functionality described on this reference page is aligned with the
ISO C standard. Any conflict between the requirements described here
and the ISO C standard is unintentional. This volume of POSIX.1‐2008
defers to the ISO C standard.
The fsetpos() function shall set the file position and state indicators
for the stream pointed to by stream according to the value of the
object pointed to by pos, which the application shall ensure is a value
obtained from an earlier call to fgetpos() on the same stream. If a
read or write error occurs, the error indicator for the stream shall be
set and fsetpos() fails.
A successful call to the fsetpos() function shall clear the end-of-file
indicator for the stream and undo any effects of ungetc() on the same
stream. After an fsetpos() call, the next operation on an update stream
may be either input or output.
The behavior of fsetpos() on devices which are incapable of seeking is
implementation-defined. The value of the file offset associated with
such a device is undefined.
The fsetpos() function shall not change the setting of errno if suc‐
The fsetpos() function shall return 0 if it succeeds; otherwise, it
shall return a non-zero value and set errno to indicate the error.
The fsetpos() function shall fail if, either the stream is unbuffered
or the stream's buffer needed to be flushed, and the call to fsetpos()
causes an underlying lseek() or write() to be invoked, and:
EAGAIN The O_NONBLOCK flag is set for the file descriptor and the
thread would be delayed in the write operation.
EBADF The file descriptor underlying the stream file is not open for
writing or the stream's buffer needed to be flushed and the file
is not open.
EFBIG An attempt was made to write a file that exceeds the maximum
EFBIG An attempt was made to write a file that exceeds the file size
limit of the process.
EFBIG The file is a regular file and an attempt was made to write at
or beyond the offset maximum associated with the corresponding
EINTR The write operation was terminated due to the receipt of a sig‐
nal, and no data was transferred.
EIO A physical I/O error has occurred, or the process is a member of
a background process group attempting to perform a write() to
its controlling terminal, TOSTOP is set, the calling thread is
not blocking SIGTTOU, the process is not ignoring SIGTTOU, and
the process group of the process is orphaned. This error may
also be returned under implementation-defined conditions.
ENOSPC There was no free space remaining on the device containing the
EPIPE An attempt was made to write to a pipe or FIFO that is not open
for reading by any process; a SIGPIPE signal shall also be sent
to the thread.
ESPIPE The file descriptor underlying stream is associated with a pipe,
FIFO, or socket.
The fsetpos() function may fail if:
ENXIO A request was made of a nonexistent device, or the request was
outside the capabilities of the device.
The following sections are informative.
Section 2.5, Standard I/O Streams, fopen(), ftell(), lseek(), rewind(),
The Base Definitions volume of POSIX.1‐2008, <stdio.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
IEEE/The Open Group 2013 FSETPOS(3P)