log, logf, logl - Natural logarithm

Definition	#include <math.h> double log(double x); float logf(double x); (C11) long double logl(long double x); (C11) These functions calculate the natural logarithm of the positive floating-point number x to the base e.
Return val.	ln(x)	for positive x.
	-HUGE_VAL -HUGE_VALF -HUGE_VALL	depending on the function type, if x is less than or equal to 0. In addition, errno is set to EDOM (domain error) or if x is equal to 0. In addition, errno is set to ERANGE.
Example	#include <math.h> #include <stdio.h> int main(void) { double x; printf("Example of log(x): Please enter x\n"); if(scanf("%lf", &x) == 1) printf("x = %g log(x) = %g\n", x, log(x)); return 0; }
See also	log2, log10, exp, exp2