LOG2
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
Page Index
NAME
log2, log2f, log2l - base-2 logarithmic function
SYNOPSIS
#include <math.h>
double log2(double x);
float log2f(float x);
long double log2l(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
log2(),
log2f(),
log2l():
-
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
DESCRIPTION
These functions return the base 2 logarithm of
x.
RETURN VALUE
On success, these functions return the base 2 logarithm of
x.
For special cases, including where
x
is 0, 1, negative, infinity, or NaN, see
log(3).
ERRORS
See
math_error(7)
for information on how to determine whether an error has occurred
when calling these functions.
For a discussion of the errors that can occur for these functions, see
log(3).
VERSIONS
These functions first appeared in glibc in version 2.1.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
log2(),
log2f(),
log2l()
| Thread safety | MT-Safe
|
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning
double
also conforms to
SVr4, 4.3BSD.
SEE ALSO
cbrt(3),
clog2(3),
log(3),
log10(3),
sqrt(3)
COLOPHON
This page is part of release 5.10 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.