log2 (3)

#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

The log2() function returns the base 2 logarithm of x.

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).

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).

These functions first appeared in glibc in version 2.1.

C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD.

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

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