ROUND(3) | Linux Programmer's Manual | ROUND(3) |

# NAME

round, roundf, roundl - round to nearest integer, away from zero# SYNOPSIS

**#include**

<math.h>

<math.h>

**double round(double**

*x*

**);**

**float roundf(float**

*x*

**);**

**long double roundl(long double**

*x*

**);**

*-lm*.

Feature Test Macro Requirements for glibc (see

**feature_test_macros**(7)):

**round**(),

**roundf**(),

**roundl**():

_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or

*cc -std=c99*# DESCRIPTION

These functions round*x*to the nearest integer, but round halfway cases away from zero (regardless of the current rounding direction, see

**fenv**(3)), instead of to the nearest even integer like

**rint**(3).

*round(0.5)*is 1.0, and

*round(-0.5)*is -1.0.

# RETURN VALUE

These functions return the rounded integer value.*x*is integral, +0, -0, NaN, or infinite,

*x*itself is returned.

# ERRORS

No errors occur. POSIX.1-2001 documents a range error for overflows, but see NOTES.# VERSIONS

These functions first appeared in glibc in version 2.1.# ATTRIBUTES

## Multithreading (see pthreads(7))

The**round**(),

**roundf**(), and

**roundl**() functions are thread-safe.

# CONFORMING TO

C99, POSIX.1-2001.# NOTES

POSIX.1-2001 contains text about overflow (which might set*errno*to

**ERANGE**, or raise an

**FE_OVERFLOW**exception). In practice, the result cannot overflow on any current machine, so this error-handling stuff is just nonsense. (More precisely, overflow can happen only when the maximum value of the exponent is smaller than the number of mantissa bits. For the IEEE-754 standard 32-bit and 64-bit floating-point numbers the maximum value of the exponent is 128 (respectively, 1024), and the number of mantissa bits is 24 (respectively, 53).)

**lround**(3) instead.

# SEE ALSO

**ceil**(3),

**floor**(3),

**lround**(3),

**nearbyint**(3),

**rint**(3),

**trunc**(3)

# COLOPHON

This page is part of release 3.53 of the Linux*man-pages*project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

2013-06-21 |