fmod(3) — Linux manual pages

Linux manual pages	Section 3: Subroutines

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`():
`_BSD_SOURCE` \|\| `_SVID_SOURCE` \|\| `_XOPEN_SOURCE` >= 600 \|\| `_ISOC99_SOURCE` \|\| `_POSIX_C_SOURCE` >= 200112L;
or cc `-std=c99`

	Note
	Link with `−lm`.

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.

COLOPHON

This page is part of release 3.52 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/.

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

%%%LICENSE_START(VERBATIM)
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working
professionally.

Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.
%%%LICENSE_END

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)