NAME¶

log2, log2f, log2l - base-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);

log2(), log2f(), log2l():

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION¶

These functions return 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 were added in glibc 2.1.

ATTRIBUTES¶

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

STANDARDS¶

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning double also conforms to SVr4, 4.3BSD.

SEE ALSO¶

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