fmod(3) Linux Man Page - System Grab Bag

Name

fmod, fmodf, fmodl - floating-point remainder function

Library

Math library ( libm ", " -lm )

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 <= 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). allbox; lbx lb lb T{ fmod()fmodf()fmodl()

Interface	Attribute	Value
T}	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.

Bugs

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