ROUND(3)

NAME
round, roundf, roundl - round to nearest integer, away from zero

SYNOPSIS
#include <math.h>

double round(double x);
float roundf(float x);
long double roundl(long double x);

Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

round(), roundf(), roundl(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; 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), instead of to the nearest even integer like rint(3).

RETURN VALUE
The rounded integer value. If x is integral or infinite, x itself is returned.

ERRORS
No errors other than EDOM and ERANGE can occur. If x is NaN, then NaN is returned and errno may be set to EDOM.

CONFORMING TO
C99.

NOTES
POSIX.1-2001 contains text about overflow (which might set errno to ERANGE, or raise an 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 (resp. 1024), and the number of mantissa bits is 24 (resp. 53).)

SEE ALSO
ceil(3), floor(3), lround(3), nearbyint(3), rint(3), trunc(3)

COLOPHON
This page is part of release 2.70 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/.