LOG2
Section: Linux Programmer's Manual (3)
Updated: 2008-08-11
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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():
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or
cc -std=c99
DESCRIPTION
The
log2()
function returns 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.
CONFORMING TO
C99, POSIX.1-2001.
The variant returning
double
also conforms to
SVr4, 4.3BSD, C89.
SEE ALSO
cbrt(3),
clog2(3),
sqrt(3)
COLOPHON
This page is part of release 3.22 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.