### 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 ***x***);**

Link with *-lm*.

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

**gamma**(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE
**gammaf**(), **gammal**(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600

### 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).

### CONFORMING TO

Because of historical variations in behavior across systems, this function is not specified in any standard.

### 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

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