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# Technical Reference: Base Operating System and Extensions, Volume 1

## log10, log10f, or log10l Subroutine

### Purpose

Computes the Base 10 logarithm.

### Syntax

#include <math.h>
float log10f (x)
float x;
long double log10l (x)
long double x;
double log10 (x)
double x;

### Description

The log10f, log10l, and log10 subroutines compute the base 10 logarithm of the x parameter, log_{10} (x).

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

### Parameters

x |
Specifies the value to be computed. |

### Return Values

Upon successful completion, the log10, log10f, and log10l, subroutines return the base
10 logarithm of x.

If x is ±0, a pole error occurs and log10, log10f, and log10l subroutines 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 occurs, and a NaN is
returned.

If x is NaN, a NaN is returned.

If x is 1, +0 is returned.

If x is +Inf, +Inf is returned.

### Error Codes

When using the libm.a library:

log10 |
If the x parameter is less than 0, the log10 subroutine returns a NaNQ value
and sets errno to EDOM. If x=
0, the log10 subroutine returns a -HUGE_VAL value but does not modify errno. |

When using libmsaa.a(-lmsaa):

log10 |
If the x parameter is not positive, the log10 subroutine returns a -HUGE_VAL value
and sets errno to EDOM. A message
indicating DOMAIN error (or SING error when x = 0)
is output to standard error. |

log10 |
If x < 0, log10l returns
the value NaNQ and sets errno to EDOM. If x equals 0, log10l returns the value -HUGE_VAL but does not
modify errno. |

### Related Information

feclearexcept Subroutine, fetestexcept Subroutine, class, _class, finite, isnan, or unordered Subroutines,
and madd, msub, mult, mdiv, pow, gcd, invert, rpow, msqrt, mcmp, move,
min, omin, fmin, m_in, mout, omout, fmout, m_out, sdiv, or itom Subroutine.

math.h in AIX 5L Version 5.2 Files Reference.

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