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# FMOD

Section: Linux Programmer's Manual (3)
Updated: 2008-08-05

## 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 x, long double y);
```

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

fmodf(), fmodl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99

## DESCRIPTION

The fmod() function computes 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 towards 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
An invalid floating-point exception (FE_INVALID) is raised.
These functions do not set errno for this case.
Domain error: y is zero
errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised.

## CONFORMING TO

C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.

remainder(3)

## COLOPHON

This page is part of release 3.21 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

## Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
COLOPHON

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