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copysign(3) — Linux manual page

NAME \|LIBRARY \|SYNOPSIS \|DESCRIPTION \|RETURN VALUE \|ERRORS \|ATTRIBUTES \|VERSIONS \|STANDARDS \|HISTORY \|SEE ALSO \|COLOPHON

copysign(3)              Library Functions Manualcopysign(3)

NAME top

       copysign, copysignf, copysignl - copy sign of a number

LIBRARY top

       Math library (libm,-lm)

SYNOPSIS top

#include <math.h>double copysign(doublex, doubley);float copysignf(floatx, floaty);long double copysignl(long doublex, long doubley);   Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):copysign(),copysignf(),copysignl():           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L               || /* Since glibc 2.19: */ _DEFAULT_SOURCE               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION top

       These functions return a value whose absolute value matches that       ofx, but whose sign bit matches that ofy.       For example,copysign(42.0, -1.0) andcopysign(-42.0, -1.0) both       return -42.0.

RETURN VALUE top

       On success, these functions return a value whose magnitude is       taken fromx and whose sign is taken fromy.       Ifx is a NaN, a NaN with the sign bit ofy is returned.

ERRORS top

       No errors occur.

ATTRIBUTES top

       For an explanation of the terms used in this section, seeattributes(7).       ┌──────────────────────────────────────┬───────────────┬─────────┐       │Interface│Attribute│Value│       ├──────────────────────────────────────┼───────────────┼─────────┤       │copysign(),copysignf(),copysignl() │ Thread safety │ MT-Safe │       └──────────────────────────────────────┴───────────────┴─────────┘

VERSIONS top

       On architectures where the floating-point formats are not IEEE 754       compliant, these functions may treat a negative zero as positive.

STANDARDS top

       C11, POSIX.1-2008.       This function is defined in IEC 559 (and the appendix with       recommended functions in IEEE 754/IEEE 854).

HISTORY top

       C99, POSIX.1-2001, 4.3BSD.

COLOPHON top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17copysign(3)

Pages that refer to this page:signbit(3)

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