[Go to CFHT Home Page] Man Pages
Back to Software Index  BORDER=0Manpage Top Level
    LOG2(3) manual page Table of Contents

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 3.78 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 http://www.kernel.org/doc/man-pages/.

Table of Contents