## NAME

fmod, fmodf, fmodl − floating-point remainder function

## SYNOPSIS

**#include
<math.h>**

**double
fmod(double** *x***, double** *y***);
float fmodf(float**

*x*

**, float**

*y*

**);**

long double fmodl(long double

long double fmodl(long double

*x*

**, long double**

*y*

**);**

Link with
*−lm*.

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

**fmodf**(),
**fmodl**():

_ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L

|| /* Since glibc 2.19: */ _DEFAULT_SOURCE

|| /* Glibc versions <= 2.19: */ _BSD_SOURCE ||
_SVID_SOURCE

## DESCRIPTION

These functions
compute the floating-point remainder of dividing *x* by
*y*. The return value is *x* − *n* *
*y*, where *n* is the quotient of *x* /
*y*, rounded toward zero to an integer.

## RETURN VALUE

On success,
these functions return the value
*x *− *n***y*, for some
integer *n*, such that the returned value has the same
sign as *x* and a magnitude less than the magnitude of
*y*.

If *x* or
*y* is a NaN, a NaN is returned.

If *x* is
an infinity, a domain error occurs, and a NaN is
returned.

If *y* is
zero, a domain error occurs, and a NaN is returned.

If *x* is
+0 (−0), and *y* is not zero, +0 (−0) is
returned.

## ERRORS

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following
errors can occur:

Domain error: *x* is an infinity

*errno* is set to
**EDOM** (but see BUGS). An invalid floating-point
exception (**FE_INVALID**) is raised.

Domain error: *y* is
zero

*errno* is set to
**EDOM**. An invalid floating-point exception
(**FE_INVALID**) is raised.

## ATTRIBUTES

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

## CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.

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

## BUGS

Before version
2.10, the glibc implementation did not set *errno* to
**EDOM** when a domain error occurred for an infinite
*x*.

## SEE ALSO

## COLOPHON

This page is
part of release 4.16 of the Linux *man-pages* project.
A description of the project, information about reporting
bugs, and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.