NAME

       log2, log2f, log2l - base-2 logarithmic function

LIBRARY

       Math library (libm, -lm)

SYNOPSIS

       #include <math.h>

       double log2(double x);
       float log2f(float x);
       long double log2l(long double x);

   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).

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌───────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                      │ Attribute     │ Value   │
       ├───────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │log2(), log2f(), log2l()                                       │ Thread safety │ MT-Safe │
       └───────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       glibc 2.1.  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)