## Linux and UNIX Man Pages

Test Your Knowledge in Computers #282
Difficulty: Easy
Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources.
True or False?

# log(3m) [opensolaris man page]

```log(3M) 						  Mathematical Library Functions						   log(3M)

NAME
log, logf, logl - natural logarithm function

SYNOPSIS
c99 [ flag... ] file... -lm [ library... ]
#include <math.h>

double log(double x);

float logf(float x);

long double logl(long double x);

DESCRIPTION
These functions compute the natural logarithm of their argument x, log(e)(x).

RETURN VALUES
Upon successful completion, log() returns the natural logarithm of x.

If x is +-0, a pole error occurs and log(), logf(), and logl() return -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.

For finite values of x that are less than 0, or if x is -Inf, a domain error occurs and a NaN is returned.

If x is NaN, a NaN is returned.

If x is 1, +0 is returned.

If x is +Inf, x is returned.

For exceptional cases, matherr(3M) tabulates the values to be returned by log() as specified by SVID3 and XPG3.

ERRORS
These functions will fail if:

Domain Error    The finite value of x is negative, or x is -Inf.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the invalid floating-point exception is raised.

The log() function sets errno to EDOM if the value of x is negative.

Pole Error      The value of x is 0.

If  the	integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the divide-by-zero floating-point exception is
raised.

USAGE
An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before  calling	these  functions.  On  return,	if
fetestexcept(FE_INVALID	|  FE_DIVBYZERO  |  FE_OVERFLOW  |  FE_UNDERFLOW) is non-zero, an exception has been raised. An application should
either examine the return value or check the floating point exception flags to detect exceptions.

An application can also set errno to 0 before calling log(). On return, if errno is non-zero, an error has occurred. The logf() and  logl()
functions do not set errno.

ATTRIBUTES
See attributes(5) for descriptions of the following attributes:

+-----------------------------+-----------------------------+
|      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
+-----------------------------+-----------------------------+
|Interface Stability	     |Standard			   |
+-----------------------------+-----------------------------+
|MT-Level		     |MT-Safe			   |
+-----------------------------+-----------------------------+

exp(3M), feclearexcept(3M), fetestexcept(3M), isnan(3M), log10(3M), log1p(3M), math.h(3HEAD), matherr(3M), attributes(5), standards(5)

SunOS 5.11							    12 Jul 2006 							   log(3M)```

## Check Out this Related Man Page

```log(3M) 						  Mathematical Library Functions						   log(3M)

NAME
log, logf, logl - natural logarithm function

SYNOPSIS
c99 [ flag... ] file... -lm [ library... ]
#include <math.h>

double log(double x);

float logf(float x);

long double logl(long double x);

DESCRIPTION
These functions compute the natural logarithm of their argument x, log(e)(x).

RETURN VALUES
Upon successful completion, log() returns the natural logarithm of x.

If x is +-0, a pole error occurs and log(), logf(), and logl() return -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.

For finite values of x that are less than 0, or if x is -Inf, a domain error occurs and a NaN is returned.

If x is NaN, a NaN is returned.

If x is 1, +0 is returned.

If x is +Inf, x is returned.

For exceptional cases, matherr(3M) tabulates the values to be returned by log() as specified by SVID3 and XPG3.

ERRORS
These functions will fail if:

Domain Error    The finite value of x is negative, or x is -Inf.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the invalid floating-point exception is raised.

The log() function sets errno to EDOM if the value of x is negative.

Pole Error      The value of x is 0.

If  the	integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the divide-by-zero floating-point exception is
raised.

USAGE
An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before  calling	these  functions.  On  return,	if
fetestexcept(FE_INVALID	|  FE_DIVBYZERO  |  FE_OVERFLOW  |  FE_UNDERFLOW) is non-zero, an exception has been raised. An application should
either examine the return value or check the floating point exception flags to detect exceptions.

An application can also set errno to 0 before calling log(). On return, if errno is non-zero, an error has occurred. The logf() and  logl()
functions do not set errno.

ATTRIBUTES
See attributes(5) for descriptions of the following attributes:

+-----------------------------+-----------------------------+
|      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
+-----------------------------+-----------------------------+
|Interface Stability	     |Standard			   |
+-----------------------------+-----------------------------+
|MT-Level		     |MT-Safe			   |
+-----------------------------+-----------------------------+