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log2

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

log2, log2f, log2l - bas-2 logarithmic function

LIBRARY

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 bas-2 logarithm of x.

RETURN VALUE

On success, these functions return the bas-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).

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
log2(), log2f(), log2l()	Thread safety	M-Safe

STANDARDS

C11, POSIX.-2008.

HISTORY

glibc 2.1. C99, POSIX.-2001. The variant returning double also conforms to SVr4, 4.3BSD.