Header File 

math.h  

Category 

Math Routines 

Prototype 

double log10(double x); 

long double log10l(long double x); 

Description 

log10 calculates the base ten logarithm of x. 

log10l is the long double version; it takes a long double argument and returns a long double result. 

Return Value 

On success, log10 (or log10l) returns the calculated value log base ten of x. 

If the argument x passed to these functions is real and less than 0, the global variable errno is set to

If x is 0, these functions return the value negative HUGE_VAL (log10) or _LHUGE_VAL (log10l). Error handling for these routines can be modified through the functions _matherr and _matherrl. 

Example  

#include <math.h>
#include <stdio.h>
int main(void)
{
   double result;
   double x = 800.6872;
   result = log10(x);
   printf("The common log of %lf is %lf\n", x, result);
   return 0;
}

Portability