FABS(3) Library Functions Manual FABS(3)

fabsabsolute value function

#include <math.h>

double fabs(double x);

The fabs() function computes the absolute value of x , | x |.

An application wishing to check for error situations should set errno to 0 before calling . If errno is non-zero on return, or the return value is NaN, an error has occurred.

Upon successful completion, fabs() returns the absolute value of x .

If is NaN, NaN is returned and errno may be set to [EDOM].

If the result underflows, 0 is returned and errno may be set to [ERANGE].

The fabs() function may fail if:

The value of x is NaN.
The result underflows.

No other errors will occur.

None.

None.

None.

isnan(3) , <math.h> .

Derived from Issue 1 of the SVID.

February 1997 posix.fail