log10(3p) — Linux manual page

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

PROLOG         top

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

NAME         top

log10, log10f, log10l — base 10 logarithm function

SYNOPSIS         top

#include <math.h>

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

DESCRIPTION         top

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.1‐2017 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         top

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
implementation-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         top

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.

None.

APPLICATION USAGE         top

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.

None.

FUTURE DIRECTIONS         top

None.

feclearexcept(3p), fetestexcept(3p), isnan(3p), log(3p), pow(3p)

The Base Definitions volume of POSIX.1‐2017, Section 4.20,
Treatment of Error Conditions for Mathematical Functions,
math.h(0p)

Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group.  In the event of any
discrepancy between this version and the original IEEE and The
Open Group Standard, the original IEEE and The Open Group
Standard is the referee document. The original Standard can be
obtained online at http://www.opengroup.org/unix/online.html .