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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, 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.

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).)

       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 3.24 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/.

                                  2008-08-11                          ROUND(3)