Section (3) round
round, roundf, roundl — round to nearest integer, away from zero
||long double x
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).
round(0.5) is 1.0, and
These functions return the rounded integer value.
x is integral,
+0, −0, NaN, or infinite,
x itself is returned.
For an explanation of the terms used in this section, see attributes(7).
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,
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.
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Copyright 2001 Andries Brouwer <aebcwi.nl>.
and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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