# FreeBSD Manual Pages

```LOG(3)			 BSD Library Functions Manual			LOG(3)

NAME
log, logf,	logl, log10, log10f, log10l, log2, log2f, log2l, log1p,
log1pf, log1pl -- logarithm functions

LIBRARY
Math Library (libm, -lm)

SYNOPSIS
#include <math.h>

double
log(double	x);

float
logf(float	x);

long double
logl(long double x);

double
log10(double x);

float
log10f(float x);

long double
log10l(long double	x);

double
log2(double x);

float
log2f(float x);

long double
log2l(long	double x);

double
log1p(double x);

float
log1pf(float x);

long double
log1pl(long double	x);

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

The log10(), log10f(), and	log10l() functions compute the logarithm base
10	of x, while log2(), log2f(), and log2l() compute the logarithm base 2
of	x.

The log1p(), log1pf(), and	log1pl() functions compute the natural loga-
rithm of 1	+ x.  Computing	the natural logarithm as log1p(x) is more ac-
curate 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 ex-
ception, and -infinity is returned.  Otherwise, attempting	to take	the
logarithm of a negative number results in an invalid exception and	a re-
turn value	of NaN.

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

STANDARDS
The log(),	logf(),	logl(),	log10(), log10f(), log10l(), log2(), log2f(),
log2l(), log1p(), log1pf(), and log1pl() functions	conform	to ISO/IEC
9899:1999 ("ISO C99").

BSD				 June 3, 2013				   BSD
```

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+12.0-RELEASE+and+Ports>