# copysign man page

## Prolog

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

copysign, copysignf, copysignl — number manipulation function

## 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*);

## Description

The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1‐2008 defers to the ISO C standard.

These functions shall produce a value with the magnitude of *x* and the sign of *y*. On implementations that represent a signed zero but do not treat negative zero consistently in arithmetic operations, these functions regard the sign of zero as positive.

## Return Value

Upon successful completion, these functions shall return a value with the magnitude of *x* and the sign of *y*.

## Errors

No errors are defined.

*The following sections are informative.*

## See Also

*signbit()*

The Base Definitions volume of POSIX.1‐2008, **<math.h>**

## Copyright

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.unix.org/online.html .