# log10, log10f, log10l

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< c‎ | numeric‎ | math

Defined in header ``<math.h>`` |  |
float log10f( float arg ); | (1) | (since C99)
double log10( double arg ); | (2) |
long double log10l( long double arg ); | (3) | (since C99)
Defined in header ``<tgmath.h>`` |  |
#define log10( arg ) | (4) | (since C99)

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

arg | - | floating-point value

### 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

Run this code

    #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");
    }

Possible output:

    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

- C23 standard (ISO/IEC 9899:2024):

  - 7.12.6.8 The log10 functions (p: TBD)

  - 7.25 Type-generic math <tgmath.h> (p: TBD)

  - F.10.3.8 The log10 functions (p: TBD)

- C17 standard (ISO/IEC 9899:2018):

  - 7.12.6.8 The log10 functions (p: 179)

  - 7.25 Type-generic math <tgmath.h> (p: 272-273)

  - F.10.3.8 The log10 functions (p: 380)

- C11 standard (ISO/IEC 9899:2011):

  - 7.12.6.8 The log10 functions (p: 245)

  - 7.25 Type-generic math <tgmath.h> (p: 373-375)

  - F.10.3.8 The log10 functions (p: 522)

- C99 standard (ISO/IEC 9899:1999):

  - 7.12.6.8 The log10 functions (p: 225-226)

  - 7.22 Type-generic math <tgmath.h> (p: 335-337)

  - F.9.3.8 The log10 functions (p: 459)

- C89/C90 standard (ISO/IEC 9899:1990):

  - 4.5.4.5 The log10 function

### See also

loglogflogl (C99)(C99) | computes natural (base-e) logarithm (\({\small \ln{x} }\)ln(x)) (function)
log2log2flog2l (C99)(C99)(C99) | computes base-2 logarithm (\({\small \log_{2}{x} }\)log2(x)) (function)
log1plog1pflog1pl (C99)(C99)(C99) | computes natural (base-e) logarithm of 1 plus the given number (\({\small \ln{(1+x)} }\)ln(1+x)) (function)
C++ documentation for log10

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