round(3) - Linux manual page (original) (raw)
round(3) Library Functions Manual round(3)
NAME top
round, roundf, roundl - round to nearest integer, away from zeroLIBRARY top
Math library (_libm_, _-lm_)SYNOPSIS top
**#include <math.h>**
**double round(double** _x_**);**
**float roundf(float** _x_**);**
**long double roundl(long double** _x_**);**Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
**round**(), **roundf**(), **roundl**():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112LDESCRIPTION top
These functions round _x_ to the nearest integer, but round halfway
cases away from zero (regardless of the current rounding
direction, see [fenv(3)](../man3/fenv.3.html)), instead of to the nearest even integer
like [rint(3)](../man3/rint.3.html).
For example, _round(0.5)_ is 1.0, and _round(-0.5)_ is -1.0.RETURN VALUE top
These functions return the rounded integer value.
If _x_ is integral, +0, -0, NaN, or infinite, _x_ itself is returned.ERRORS top
No errors occur.ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ **Interface** │ **Attribute** │ **Value** │
├──────────────────────────────────────┼───────────────┼─────────┤
│ **round**(), **roundf**(), **roundl**() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘STANDARDS top
C11, POSIX.1-2008.HISTORY top
glibc 2.1. C99, POSIX.1-2001.
POSIX.1-2001 contains text about overflow (which might set _[errno](../man3/errno.3.html)_
to **ERANGE**, or raise an **FE_OVERFLOW** exception). In practice, the
result cannot overflow on any current machine, so this error-
handling stuff was 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
127 (respectively, 1023), and the number of mantissa bits
including the implicit bit is 24 (respectively, 53).) This was
removed in POSIX.1-2008.
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)](../man3/lround.3.html)
instead.SEE ALSO top
[ceil(3)](../man3/ceil.3.html), [floor(3)](../man3/floor.3.html), [lround(3)](../man3/lround.3.html), [nearbyint(3)](../man3/nearbyint.3.html), [rint(3)](../man3/rint.3.html), [trunc(3)](../man3/trunc.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 round(3)
Pages that refer to this page:ceil(3), floor(3), lrint(3), lround(3), rint(3), roundup(3), trunc(3)