fabs, fabsf, fabsl - absolute value of floating-point number

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ fabs(), fabsf(), fabsl()                                                    │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

       These functions return the absolute value of the floating-point number x.

       No errors occur.

       C99, POSIX.1-2001.

       The variant returning double also conforms to SVr4, 4.3BSD, C89.

       Math library (libm, -lm)

       fabs, fabsf, fabsl - absolute value of floating-point number

       These functions return the absolute value of x.

       If x is a NaN, a NaN is returned.

       If x is -0, +0 is returned.

       If x is negative infinity or positive infinity, positive infinity is returned.

abs(3), cabs(3), ceil(3), floor(3), labs(3), rint(3)

Linux man-pages 6.9.1                              2024-05-02                                            fabs(3)

       C11, POSIX.1-2008.

#include<math.h>doublefabs(doublex);floatfabsf(floatx);longdoublefabsl(longdoublex);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       fabsf(), fabsl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE