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 4.15 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/.

                                            2017-09-15                                    LOG2(3)