1-3) Computes the common (base-10) logarithm of arg.

4) Type-generic macro: If arg has type long double, log10l is called. Otherwise, if arg has integer type or the type double, log10 is called. Otherwise, log10f is called.

Parameters

Return value

If no errors occur, the common (base-10) logarithm of arg (log10(arg) or lg(arg)) is returned.

If a domain error occurs, an implementation-defined value is returned (NaN where supported).

If a pole error occurs, HUGE_VAL, -HUGE_VALF, or -HUGE_VALL is returned.

Error handling

Errors are reported as specified in math_errhandling.

Domain error occurs if arg is less than zero.

Pole error may occur if arg is zero.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• If the argument is ±0, -∞ is returned and FE_DIVBYZERO is raised.
• If the argument is 1, +0 is returned
• If the argument is negative, NaN is returned and FE_INVALID is raised.
• If the argument is +∞, +∞ is returned
• If the argument is NaN, NaN is returned.

Example

#include <errno.h>
#include <fenv.h>
#include <float.h>
#include <math.h>
#include <stdio.h>
// #pragma STDC FENV_ACCESS ON

int main(void)
{
    printf("log10(1000) = %f\n", log10(1000));
    printf("log10(0.001) = %f\n", log10(0.001));
    printf("base-5 logarithm of 125 = %f\n", log10(125) / log10(5));

    // special values
    printf("log10(1) = %f\n", log10(1));
    printf("log10(+Inf) = %f\n", log10(INFINITY));

    // error handling
    errno = 0; feclearexcept(FE_ALL_EXCEPT);
    printf("log10(0) = %f\n", log10(0));
    if (errno == ERANGE)
        perror("    errno == ERANGE");
    if (fetestexcept(FE_DIVBYZERO))
        puts("    FE_DIVBYZERO raised");
}

log10(1000) = 3.000000
log10(0.001) = -3.000000
base-5 logarithm of 125 = 3.000000
log10(1) = 0.000000
log10(+Inf) = inf
log10(0) = -inf
    errno == ERANGE: Numerical result out of range
    FE_DIVBYZERO raised

References

See also