**copysign**

**COPYSIGN(3)** Linux Programmer's Manual **COPYSIGN(3)**
NAME
copysign, copysignf, copysignl - copy sign of a number
SYNOPSIS
#include <math.h>
double copysign(double x, double y);
float copysignf(float x, float y);
long double copysignl(long double x, long double y);
Link with -lm.
Feature Test Macro Requirements for glibc (see **feature_test_macros(7)**):
copysign(), copysignf(), copysignl():
_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 600 ||
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
DESCRIPTION
These functions return a value whose absolute value matches that of x,
but whose sign bit matches that of y.
For example, copysign(42.0, -1.0) and copysign(-42.0, -1.0) both return
-42.0.
RETURN VALUE
On success, these functions return a value whose magnitude is taken
from x and whose sign is taken from y.
If x is a NaN, a NaN with the sign bit of y is returned.
ERRORS
No errors occur.
ATTRIBUTES
For an explanation of the terms used in this section, see
**attributes(7)**.
+-------------------------------------+---------------+---------+
|Interface | Attribute | Value |
+-------------------------------------+---------------+---------+
|copysign(), copysignf(), copysignl() | Thread safety | MT-Safe |
+-------------------------------------+---------------+---------+
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008. This function is defined in IEC 559
(and the appendix with recommended functions in IEEE 754/IEEE 854).
NOTES
On architectures where the floating-point formats are not IEEE 754 com-
pliant, these functions may treat a negative zero as positive.
SEE ALSO
**signbit(3)**
COLOPHON
This page is part of release 4.04 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
http://www.kernel.org/doc/man-pages/.
GNU 2015-04-19 **COPYSIGN(3)**

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