.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
.\"     <mtk.manpages@gmail.com>
.\"
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.\" 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
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.\"
.\" 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.\" manual page may be incorrect or out-of-date.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
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.\" %%%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 (faith@cs.unc.edu)
.\" Modified 2002-07-27 by Walter Harms
.\" 	(walter.harms@informatik.uni-oldenburg.de)
.\"
.TH FMOD 3  2021-03-22 "" "Linux Programmer's Manual"
.SH NAME
fmod, fmodf, fmodl \- floating-point remainder function
.SH SYNOPSIS
.nf
.B #include <math.h>
.PP
.BI "double fmod(double " x ", double " y );
.BI "float fmodf(float " x ", float " y );
.BI "long double fmodl(long double " x ", long double " y );
.fi
.PP
Link with \fI\-lm\fP.
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR fmodf (),
.BR fmodl ():
.nf
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.SH DESCRIPTION
These functions compute the floating-point remainder of dividing
.I x
by
.IR y .
The return value is
.IR x
\-
.I n
*
.IR y ,
where
.I n
is the quotient of
.I x
/
.IR y ,
rounded toward zero to an integer.
.SH RETURN VALUE
On success, these
functions return the value \fIx\fP\ \-\ \fIn\fP*\fIy\fP,
for some integer
.IR n ,
such that the returned value has the same sign as
.I x
and a magnitude less than the magnitude of
.IR y .
.PP
If
.I x
or
.I y
is a NaN, a NaN is returned.
.PP
If
.I x
is an infinity,
a domain error occurs, and
a NaN is returned.
.PP
If
.I y
is zero,
a domain error occurs, and
a NaN is returned.
.PP
If
.I x
is +0 (\-0), and
.I y
is not zero, +0 (\-0) is returned.
.SH ERRORS
See
.BR math_error (7)
for information on how to determine whether an error has occurred
when calling these functions.
.PP
The following errors can occur:
.TP
Domain error: \fIx\fP is an infinity
.I errno
is set to
.BR EDOM
(but see BUGS).
An invalid floating-point exception
.RB ( FE_INVALID )
is raised.
.TP
Domain error: \fIy\fP is zero
.I errno
is set to
.BR EDOM .
An invalid floating-point exception
.RB ( FE_INVALID )
is raised.
.\" POSIX.1 documents an optional underflow error, but AFAICT it doesn't
.\" (can't?) occur -- mtk, Jul 2008
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR fmod (),
.BR fmodf (),
.BR fmodl ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.SH CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.
.PP
The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.SH BUGS
Before version 2.10, the glibc implementation did not set
.\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6784
.I errno
to
.B EDOM
when a domain error occurred for an infinite
.IR x .
.SH SEE ALSO
.BR remainder (3)