# Manual Reference Pages  - FMOD (3)

### NAME

fmod, fmodf, fmodl - floating-point remainder function

Synopsis
Description
Errors
Bugs
Colophon

### 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 || _POSIX_C_SOURCE >= 200112L;
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 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.

### CONFORMING TO

C99, POSIX.1-2001. 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.