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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 Manual             copysign(3)

NAME         top

       copysign, copysignf, copysignl - copy sign of a number

LIBRARY         top

       Math library (libm, -lm)

SYNOPSIS         top

       #include <math.h>

       double copysign(double x, double y);
       float copysignf(float x, float y);
       long double copysignl(long double x, long double y);

   Feature Test Macro Requirements for glibc (see
   feature_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
       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         top

       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         top

       No errors occur.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).
       โ”Œโ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”ฌโ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”ฌโ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”
       โ”‚ Interface                            โ”‚ Attribute     โ”‚ Value   โ”‚
       โ”œโ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”ผโ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”ผโ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”ค
       โ”‚ copysign(), copysignf(), copysignl() โ”‚ Thread safety โ”‚ MT-Safe โ”‚
       โ””โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”ดโ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”ดโ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”˜

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.

SEE ALSO         top

       signbit(3)

COLOPHON         top

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Linux man-pages 6.18            2026-02-08                    copysign(3)

Pages that refer to this page: signbit(3)

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