## table of contents

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

# NAME¶

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

# SYNOPSIS¶

#include <math.h>

double round(doublex);float roundf(floatx);long double roundl(long doublex);

Link with *-lm*.

**round**(), **roundf**(), **roundl**():

_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

# 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).

For example, *round(0.5)* is 1.0, and *round(-0.5)* is
-1.0.

# RETURN VALUE¶

These functions return the rounded integer value.

If *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¶

For an explanation of the terms used in this section, see attributes(7).

Interface |
Attribute |
Value |

round (), roundf (), roundl () | Thread safety | MT-Safe |

# CONFORMING TO¶

C99, POSIX.1-2001, POSIX.1-2008.

# 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).)

If you want to store the rounded value in an integer type, you probably want to use one of the functions described in lround(3) instead.

# SEE ALSO¶

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

# COLOPHON¶

This page is part of release 5.13 of the Linux *man-pages*
project. A description of the project, information about reporting bugs, and
the latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.

2021-03-22 |