# log10(3p) [posix man page]

```LOG10(3P)						     POSIX Programmer's Manual							 LOG10(3P)

PROLOG
This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME
log10, log10f, log10l -- base 10 logarithm function

SYNOPSIS
#include <math.h>

double log10(double x);
float log10f(float x);
long double log10l(long double x);

DESCRIPTION
The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here
and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.

These functions shall compute the base 10 logarithm of their argument x, log10(x).

An  application	wishing  to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
functions. On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is  non-zero,  an  error
has occurred.

RETURN VALUE
Upon successful completion, these functions shall return the base 10 logarithm of x.

If x is +-0, a pole error shall occur and log10(), log10f(), and log10l() shall return -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.

For  finite values of x that are less than 0, or if x is -Inf, a domain error shall occur, and either a NaN (if supported), or an implemen-
tation-defined value shall be returned.

If x is NaN, a NaN shall be returned.

If x is 1, +0 shall be returned.

If x is +Inf, +Inf shall be returned.

ERRORS
These functions shall fail if:

Domain Error
The finite value of x is negative, or x is -Inf.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be  set  to	[EDOM].   If  the  integer
expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.

Pole Error  The value of x is zero.

If  the  integer  expression  (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE].  If the integer
expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception shall be raised.

The following sections are informative.

EXAMPLES
None.

APPLICATION USAGE
On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of  each  other,  but	at
least one of them must be non-zero.

RATIONALE
None.

FUTURE DIRECTIONS
None.

feclearexcept(), fetestexcept(), isnan(), log(), pow()

The Base Definitions volume of POSIX.1-2008, Section 4.19, Treatment of Error Conditions for Mathematical Functions, <math.h>