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.
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
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
signal, 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.
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 Electrical 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
IEEE/The Open Group 2013 FSETPOS(3P)