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round(3) — Linux manual page

NAME \|LIBRARY \|SYNOPSIS \|DESCRIPTION \|RETURN VALUE \|ERRORS \|ATTRIBUTES \|STANDARDS \|HISTORY \|SEE ALSO \|COLOPHON

round(3)                 Library Functions Manualround(3)

NAME top

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

LIBRARY top

       Math library (libm,-lm)

SYNOPSIS top

#include <math.h>double round(doublex);float roundf(floatx);long double roundl(long doublex);   Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):round(),roundf(),roundl():           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION top

       These functions roundx to the nearest integer, but round halfway       cases away from zero (regardless of the current rounding       direction, seefenv(3)), instead of to the nearest even integer       likerint(3).       For example,round(0.5) is 1.0, andround(-0.5) is -1.0.

RETURN VALUE top

       These functions return the rounded integer value.       Ifx 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, seeattributes(7).       ┌──────────────────────────────────────┬───────────────┬─────────┐       │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 seterrno       toERANGE, or raise anFE_OVERFLOWexception).  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 inlround(3)       instead.

COLOPHON top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17round(3)

Pages that refer to this page:ceil(3), floor(3), lrint(3), lround(3), rint(3), roundup(3), trunc(3)

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