FABS(3) Library Functions Manual FABS(3)

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

Math library (libm, -lm)

#include <math.h>
double fabs(double x);
float fabsf(float x);
long double fabsl(long double x);
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

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

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.

No errors occur.

For an explanation of the terms used in this section, see attributes(7).

Interface Attribute Value
fabs (), fabsf (), fabsl () Thread safety MT-Safe

C99, POSIX.1-2001, POSIX.1-2008.

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

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

2022-10-09 Linux man-pages 6.01