log10l
(3)base-10 logarithmic function
#include <math.h> double log10(double x); float log10f(float x); long double log10l(long double x); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): log10f(), log10l(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE