## NAME

gamma, gammaf, gammal − (logarithm of the) gamma function

## SYNOPSIS

**#include
<math.h>**

**double
gamma(double** *x***);
float gammaf(float**

*x*

**);**

long double gammal(long double

long double gammal(long double

*x*

**);**

Link with
*−lm*.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

**gamma**():

_XOPEN_SOURCE

|| /* Since glibc 2.19: */ _DEFAULT_SOURCE

|| /* Glibc versions <= 2.19: */ _BSD_SOURCE ||
_SVID_SOURCE

**gammaf**(),
**gammal**():

_XOPEN_SOURCE >= 600 ||
(_XOPEN_SOURCE && _ISOC99_SOURCE)

|| /* Since glibc 2.19: */ _DEFAULT_SOURCE

|| /* Glibc versions <= 2.19: */ _BSD_SOURCE ||
_SVID_SOURCE

## DESCRIPTION

These functions are deprecated: instead, use either the tgamma(3) or the lgamma(3) functions, as appropriate.

For the definition of the Gamma function, see tgamma(3).

***BSD
version**

The libm in 4.4BSD and some versions of FreeBSD had a
**gamma**() function that computes the Gamma function, as
one would expect.

**glibc
version**

Glibc has a **gamma**() function that is equivalent to
lgamma(3) and computes the natural logarithm of the
Gamma function.

## RETURN VALUE

See lgamma(3).

## ERRORS

See lgamma(3).

## ATTRIBUTES

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

## CONFORMING TO

Because of historical variations in behavior across systems, this function is not specified in any recent standard. It was documented in SVID 2.

## NOTES

**History**

4.2BSD had a **gamma**() that computed
ln(|Gamma(|*x*|)|), leaving the sign of
Gamma(|*x*|) in the external integer *signgam*. In
4.3BSD the name was changed to lgamma(3), and the man
page promises

"At some time in the future the name gamma will be rehabilitated and used for the Gamma function"

This did indeed
happen in 4.4BSD, where **gamma**() computes the Gamma
function (with no effect on *signgam*). However, this
came too late, and we now have tgamma(3), the
"true gamma" function.

## SEE ALSO

lgamma(3), signgam(3), tgamma(3)

## COLOPHON

This page is
part of release 4.16 of the Linux *man-pages* project.
A description of the project, information about reporting
bugs, and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.