LOG2Section: Linux Programmer's Manual (3)
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NAMElog2, log2f, log2l - 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)):
DESCRIPTIONThe log2() function returns the base 2 logarithm of x.
RETURN VALUEOn 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).
ERRORSSee 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).
VERSIONSThese functions first appeared in glibc in version 2.1.
CONFORMING TOC99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.
SEE ALSOcbrt(3), clog2(3), sqrt(3)
COLOPHONThis page is part of release 3.21 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/.