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.
--- get and set current rounding direction
int fesetround(int round);
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 get the current rounding direction.
function shall establish the rounding direction represented by its
If the argument is not equal to the value of a rounding direction
macro, the rounding direction is not changed.
function shall return the value of the rounding direction macro
representing the current rounding direction or a negative value if
there is no such rounding direction macro or the current rounding
direction is not determinable.
function shall return a zero value if and only if the requested
rounding direction was established.
No errors are defined.
The following sections are informative.
The following example saves, sets, and restores the rounding direction,
reporting an error and aborting if setting the rounding direction
void f(int round_dir)
#pragma STDC FENV_ACCESS ON
save_round = fegetround();
setround_ok = fesetround(round_dir);
assert(setround_ok == 0);
/* ... */
/* ... */
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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