# RINT

Section: POSIX Programmer's Manual (3P)

Updated: 2017

Page Index

## 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.

## NAME

rint,
rintf,
rintl
--- round-to-nearest integral value

## SYNOPSIS

#include <math.h>
double rint(double *x*);
float rintf(float *x*);
long double rintl(long double *x*);

## DESCRIPTION

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.

These functions shall return the integral value (represented as a
**double**)
nearest
*x*
in the direction of the current rounding mode. The current rounding
mode is implementation-defined.

If the current rounding mode rounds toward negative infinity, then
*rint*()
shall be equivalent to
*floor*().
If the current rounding mode rounds toward positive infinity, then
*rint*()
shall be equivalent to
*ceil*().
If the current rounding mode rounds towards zero, then
*rint*()
shall be equivalent to
*trunc*().
If the current rounding mode rounds towards nearest, then
*rint*()
differs from
*round*()
in that halfway cases are rounded to even rather than away from zero.

These functions differ from the
*nearbyint*(),
*nearbyintf*(),
and
*nearbyintl*()
functions only in that they may raise the inexact floating-point
exception if the result differs in value from the argument.

An application wishing to check for error situations should set
*errno*
to zero and call
*feclearexcept*(FE_ALL_EXCEPT)
before calling these functions. On return, if
*errno*
is non-zero or *fetestexcept*(FE_INVALID | FE_DIVBYZERO |
FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

## RETURN VALUE

Upon successful completion, these functions shall return the integer
(represented as a double precision number) nearest

*x*
in the direction of the current rounding mode.
The result shall have the same sign as

*x*.

If
*x*
is NaN, a NaN shall be returned.

If
*x*
is ±0 or ±Inf,
*x*
shall be returned.

## ERRORS

No errors are defined.

*The following sections are informative.*

## EXAMPLES

None.

## APPLICATION USAGE

The integral value returned by these functions need not be expressible
as an

**intmax_t**.
The return value should be tested before assigning it to an integer type
to avoid the undefined results of an integer overflow.

## RATIONALE

None.

## FUTURE DIRECTIONS

None.

## SEE ALSO

*abs*(),

*ceil*(),

*feclearexcept*(),

*fetestexcept*(),

*floor*(),

*isnan*(),

*nearbyint*()

The Base Definitions volume of POSIX.1-2017,
*Section 4.20*, *Treatment of Error Conditions for Mathematical Functions,*
**<math.h>**

## COPYRIGHT

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

http://www.opengroup.org/unix/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.kernel.org/doc/man-pages/reporting_bugs.html .