floor(3) Library Functions Manual floor(3) floor, floorf, floorl - (libm -lm) #include double floor(double x); float floorf(float x); long double floorl(long double x); glibc ( feature_test_macros(7)): floorf(), floorl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE x. floor(0.5) 0.0 floor(-0.5) -1.0. x. x +0 -0 NaN x . . attributes(7). +------------+------------------------------------+--------------------+ || | | +------------+------------------------------------+--------------------+ |floor(), | | MT-Safe | |floorf(), | | | |floorl() | | | +------------+------------------------------------+--------------------+ C11, POSIX.1-2008. C99 POSIX.1-2001. double SVr4 4.3BSD C89. SUSv2 POSIX.1-2001 ( errno ERANGE FE_OVERFLOW). . ( . IEEE-754 32 64 127 ( 1023) 24 ( 53)). POSIX.1-2008. ceil(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3) 3 . . : . 6.18 8 2026 floor(3)