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LOG(3) | Linux Programmer's Manual | LOG(3) |
NAME¶
log, logf, logl - natural logarithmic functionSYNOPSIS¶
#include <math.h>double log(double x);float logf(float x);long double logl(long double x);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_BSD_SOURCE || _SVID_SOURCE ||
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
DESCRIPTION¶
The log() function returns the natural logarithm of x.RETURN VALUE¶
On success, these functions return the natural logarithm of x.ERRORS¶
See math_error(7) for information on how to determine whether an error has occurred when calling these functions. The following errors can occur:- Domain error: x is negative
- errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised.
- Pole error: x is zero
- errno is set to ERANGE. A divide-by-zero floating-point exception (FE_DIVBYZERO) is raised.
CONFORMING TO¶
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.BUGS¶
In glibc 2.5 and earlier, taking the log() of a NaN produces a bogus invalid floating-point (FE_INVALID) exception.SEE ALSO¶
cbrt(3), clog(3), log10(3), log1p(3), log2(3), sqrt(3)COLOPHON¶
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.2010-09-20 |