Base-2 logarithmic function
#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 || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
The log2() function returns the base 2 logarithm of x.
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).
These functions first appeared in glibc in version 2.1.
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD.
This page is part of release 3.74 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 http://www.kernel.org/doc/man-pages/.