fmodf (3)
Leading comments
Copyright 1993 David Metcalfe (david@prism.demon.co.uk) and Copyright 2008, Linux Foundation, written by Michael Kerrisk <mtk.manpages@gmail.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 ...
NAME
fmod, fmodf, fmodl  floatingpoint remainder functionSYNOPSIS
#include <math.h> double fmod(double x, double y);
float fmodf(float x, float y);
long double fmodl(long double x, long double y);
Link with lm.
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
DESCRIPTION
These functions compute the floatingpoint 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 floatingpoint exception (FE_INVALID) is raised.
 Domain error: y is zero
 errno is set to EDOM. An invalid floatingpoint 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  MTSafe 
CONFORMING TO
C99, POSIX.12001, POSIX.12008.The variant returning double also conforms to SVr4, 4.3BSD, C89.