ceil(3) Library Functions Manual ceil(3) ceil, ceilf, ceill - , , LIBRARY Math library (libm, -lm) #include double ceil(double x); float ceilf(float x); long double ceill(long double x); glibc (. feature_test_macros(7)): ceilf(), ceill(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE , x. , ceil(0.5) 1.0, ceil(-0.5) -0.0. x. x , +0, -0, NaN , x. . POSIX.1-2001 , . attributes(7). +----------------------------+----------------------------------------------------------+--------------------------+ | | | | +----------------------------+----------------------------------------------------------+--------------------------+ |ceil(), ceilf(), ceill() | | MT-Safe | +----------------------------+----------------------------------------------------------+--------------------------+ C11, POSIX.1-2008. C99, POSIX.1-2001. , double, SVr4, 4.3BSD, C89. SUSv2 and POSIX.1-2001 contain 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 127 (respectively, 1023), and the number of mantissa bits including the implicit bit is 24 (respectively, 53).) , , (int, long ). , , , . . floor(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3) Azamat Hackimov , Dmitriy S. Seregin , Dmitry Bolkhovskikh , Katrin Kutepova , Yuri Kozlov ; GNU 3 , . . , , . Linux man-pages 6.06 31 2023 . ceil(3)