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# fmod(3)

2017-09-15
Aliases: fmodf(3), fmodf(3), fmodf(3), fmodf(3), fmodf(3), fmodf(3), fmodf(3), fmodf(3), fmodf(3), fmodf(3), fmodl(3), fmodl(3), fmodl(3), fmodl(3), fmodl(3), fmodl(3), fmodl(3), fmodl(3), fmodl(3), fmodl(3)

### manpages-dev

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### man-pages

Linux kernel and C library user-space interface documentation

## 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():
_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).
 Interface Attribute Value Thread safety MT-Safe

## 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.