Name
log2, log2f, log2l - base-2 logarithmic functionLibrary
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 ofx. Return Value
On success, these functions return the base 2 logarithm ofx. 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 |
| T} | 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.