NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | ATTRIBUTES | CONFORMING TO | SEE ALSO | COLOPHON

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

NAME         top

       log2, log2f, log2l - base-2 logarithmic function

SYNOPSIS         top

       #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         top

       These functions return the base 2 logarithm of x.

RETURN VALUE         top

       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         top

       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         top

       These functions first appeared in glibc in version 2.1.

ATTRIBUTES         top

       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         top

       C99, POSIX.1-2001, POSIX.1-2008.

       The variant returning double also conforms to SVr4, 4.3BSD.

SEE ALSO         top

       cbrt(3), clog2(3), log(3), log10(3), sqrt(3)

COLOPHON         top

       This page is part of release 4.08 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/.

                                 2016-03-15                          LOG2(3)