`log`

, `logf`

---natural logarithms#include <math.h> double log(doublex); float logf(floatx);

**Description**

Return the natural logarithm of `x`, that is, its logarithm base e
(where e is the base of the natural system of logarithms, 2.71828...).
`log`

and `logf`

are identical save for the return and argument types.

You can use the (non-ANSI) function `matherr`

to specify error
handling for these functions.

**Returns**

Normally, returns the calculated value. When `x` is zero, the
returned value is `-HUGE_VAL`

and `errno`

is set to `ERANGE`

.
When `x` is negative, the returned value is `-HUGE_VAL`

and
`errno`

is set to `EDOM`

. You can control the error behavior via
`matherr`

.

**Portability**

`log`

is ANSI, `logf`

is an extension.

Go to the first, previous, next, last section, table of contents.