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LOG2(3)                    Linux Programmer's Manual                   LOG2(3)

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 ||
           _POSIX_C_SOURCE >= 200112L;
           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.
SEE ALSO
       cbrt(3), clog2(3), log(3), log10(3), sqrt(3)
COLOPHON
       This page is part of release 3.53 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/.

                                  2010-09-12                           LOG2(3)