Section: POSIX Programmer's Manual (3P)
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.
--- 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.1-2017 defers to the ISO C standard.
function shall set the file position and state indicators for the
stream pointed to by
according to the value of the object pointed to by
which the application shall ensure is a value obtained from an earlier
on the same stream. If a read or write error occurs, the error
indicator for the stream shall be set and
A successful call to the
function shall clear the end-of-file indicator for the stream and
undo any effects of
on the same stream. After an
call, the next operation on an update stream may be either input or
The behavior of
on devices which are incapable of seeking is implementation-defined.
The value of the file offset associated with such a device is
function shall not change the setting of
function shall return 0 if it succeeds; otherwise, it shall return
a non-zero value and set
to indicate the error.
function shall fail if,
is unbuffered or the
buffer needed to be flushed, and the call to
causes an underlying
to be invoked, and:
The O_NONBLOCK flag is set for the file descriptor and the thread
would be delayed in the write operation.
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.
An attempt was made to write a file that exceeds the maximum file size.
An attempt was made to write a file that exceeds the file size
limit of the process.
The file is a regular file and an attempt was made to write at or
beyond the offset maximum associated with the corresponding stream.
The write operation was terminated due to the receipt of a signal,
and no data was transferred.
A physical I/O error has occurred, or the process is a member of a
background process group attempting to perform a
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.
There was no free space remaining on the device containing the file.
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.
The file descriptor underlying
is associated with a pipe, FIFO, or socket.
function may fail if:
A request was made of a nonexistent device, or the request was outside
the capabilities of the device.
The following sections are informative.
, Standard I/O Streams,
The Base Definitions volume of POSIX.1-2017,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
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
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