|LOG(3)||Linux Programmer's Manual||LOG(3)|
NAMElog, logf, logl - natural logarithmic function
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
DESCRIPTIONThe log() function returns the natural logarithm of x.
RETURN VALUEOn success, these functions return the natural logarithm of x.
ERRORSSee 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 TOC99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.
BUGSIn glibc 2.5 and earlier, taking the log() of a NaN produces a bogus invalid floating-point ( FE_INVALID) exception.
SEE ALSOcbrt(3), clog(3), log10(3), log1p(3), log2(3), sqrt(3)
COLOPHONThis page is part of release 3.53 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/.