modf(3) Library Functions Manual modf(3) modf, modff, modfl - (libm -lm) #include double modf(double x, double *iptr); float modff(float x, float *iptr); long double modfl(long double x, long double *iptr); glibc ( feature_test_macros(7)): modff(), modfl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE x x. iptr. x. x NaN NaN *iptr NaN. x ( ) +0 (-0) *iptr ( ). . attributes(7). +------------+------------------------------------+--------------------+ || | | +------------+------------------------------------+--------------------+ |modf(), | | MT-Safe | |modff(), | | | |modfl() | | | +------------+------------------------------------+--------------------+ C11, POSIX.1-2008. C99 POSIX.1-2001. double SVr4 4.3BSD C89. frexp(3), ldexp(3) 3 . . : . 6.18 8 2026 modf(3)