# FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
LOG(3)		       FreeBSD Library Functions Manual			LOG(3)

NAME
log, logf,	logl, log10, log10f, log2, log2f, log1p, log1pf	-- logarithm
functions

LIBRARY
Math Library (libm, -lm)

SYNOPSIS
#include <math.h>

double
log(double	x);

float
logf(float	x);

double
log10(double x);

float
log10f(float x);

double
log2(double x);

float
log2f(float x);

double
log1p(double x);

float
log1pf(float x);

DESCRIPTION
The log() and logf() functions compute the	natural	logarithm of x.

The log10() and log10f() functions	compute	the logarithm base 10 of x,
while log2() and log2f() compute the logarithm base 2 of x.

The log1p() and log1pf() functions	compute	the natural logarithm of 1 +
x.	 Computing the natural logarithm as log1p(x) is	more accurate than
computing it as log(1 + x)	when x is close	to zero.

RETURN VALUES
These functions return the	requested logarithm; the logarithm of 1	is +0.
An	attempt	to take	the logarithm of +-0 results in	a divide-by-zero
exception,	and -infinity is returned.  Otherwise, attempting to take the
logarithm of a negative number results in an invalid exception and	a
return value of NaN.

exp(3), ilogb(3), math(3),	pow(3)

STANDARDS
The log(),	logf(),	log10(), log10f(), log2(), log2f(), log1p(), and
log1pf() functions	conform	to ISO/IEC 9899:1999 (``ISO C99'').

FreeBSD	10.3		       December	5, 2010			  FreeBSD 10.3

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | SEE ALSO | STANDARDS

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=log&sektion=3&manpath=FreeBSD+9.2-RELEASE>

home | help