# round (3p) - Linux Manuals

## round: round to the nearest integer value in a floating-point

## 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

round, roundf, roundl - round to the nearest integer value in a floating-point format

## SYNOPSIS

**#include <math.h>
**

**
double round(double** *x***);
float roundf(float**

*x*

**);**

long double roundl(long double

long double roundl(long double

*x*

**);**

## DESCRIPTION

These functions shall round their argument to the nearest integer value in floating-point format, rounding halfway cases away from zero, regardless of the current rounding direction.

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 rounded integer value.

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

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

If the correct value would cause overflow, a range error shall occur
and *round*(), *roundf*(), and *roundl*() shall
return the value of the macro ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL
(with the same sign as *x*),
respectively.

## ERRORS

These functions may fail if:

- Range Error
- The result overflows.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then *errno* shall be set to [ERANGE]. If the
integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
then the overflow floating-point exception shall be raised.

*The following sections are informative.*

## EXAMPLES

## APPLICATION USAGE

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.

## RATIONALE

## FUTURE DIRECTIONS

## COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 .

## SEE ALSO

*feclearexcept*(), *fetestexcept*(), the Base
Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment
of
Error Conditions for Mathematical Functions, *<math.h>*