modf, modff, modfl - extract signed integral and fractional values from floating-point number

#include <math.h>

double modf(double x, double *iptr);
float modff(float x, float *iptr);
long double modfl(long double x, long double *iptr);

Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

These functions break the argument x into an integral part and a fractional part, each of which has the same sign as x. The integral part is stored in the location pointed to by iptr.

These functions return the fractional part of x.

If x is a NaN, a NaN is returned, and *iptr is set to a NaN.

If x is positive infinity (negative infinity), +0 (-0) is returned, and *iptr is set to positive infinity (negative infinity).

frexp(3), ldexp(3)