log2(3) - Linux man page

Name

log2, log2f, log2l - base-2 logarithmic function

#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.