NAME

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

LIBRARY

       Math library (libm, -lm)

SYNOPSIS

       #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 >= 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.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ round(), roundf(), roundl()                                                 │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       glibc 2.1.  C99, POSIX.1-2001.

       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
       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) instead.

SEE ALSO

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

Linux man-pages 6.9.1                              2024-06-16                                           round(3)