fabsf
(3)absolute value of floating-point number
#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