modf(3) - BetterMan

modf(3)

extract signed integral and fractional values from floating-point number

distropkg manpages-dev@6.9.1-1dataset 2026-04-01T06:19:02Z+debian+ec4110e+mandoc:1.14.6-4

Synopsis

#include <math.h>
double modf(double 
x
, double *
iptr
);
float modff(float 
x
, float *
iptr
);
long double modfl(long double 
x
, long double *
iptr
);
modff
(), 
modfl
():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

—

NAME

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

LIBRARY

Math library (libm, -lm)

SYNOPSIS

bash

#include <math.h>

bash

double modf(double \nx\n, double *\niptr\n);\n
\nfloat modff(float \nx\n, float *\niptr\n);\n
\nlong double modfl(long double \nx\n, long double *\niptr\n);

modff(), modfl():

bash


\n
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
\n
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
\n
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

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.

RETURN VALUE

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).

ERRORS

No errors occur.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
modf (), modff (), modfl ()	Thread safety	MT-Safe

STANDARDS

C11, POSIX.1-2008.

HISTORY

C99, POSIX.1-2001.

The variant returning double also conforms to SVr4, 4.3BSD, C89.