fmod(3) — Linux manual pages

Linux manual pages	Section 3

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)`;

Note

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`

	Note
	Link with `−lm`.

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
`fmod`(), `fmodf`(), `fmodl`()	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.

COLOPHON

This page is part of release 5.11 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/.

  Copyright 1993 David Metcalfe (davidprism.demon.co.uk)
and Copyright 2008, Linux Foundation, written by Michael Kerrisk
    <mtk.manpagesgmail.com>

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References consulted:
    Linux libc source code
    Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
    386BSD man pages
Modified 1993-07-24 by Rik Faith (faithcs.unc.edu)
Modified 2002-07-27 by Walter Harms
(walter.harmsinformatik.uni-oldenburg.de)