log(3) Library Functions Manual log(3) log, logf, logl - (libm, -lm) #include double log(double x); float logf(float x); long double logl(long double x); glibc (. feature_test_macros(7)): logf(), logl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE x. x. x NaN, NaN. x 1, +0. x , . x , , -HUGE_VAL, -HUGE_VALF -HUGE_VALL, . x ( ), , NaN (Not a Number, ). math_error(7), , . : Domain error: x is negative errno EDOM. (FE_INVALID). Pole error: x is zero errno ERANGE. (FE_DIVBYZERO). attributes(7). +----------------------------+----------------------------------------------------------+--------------------------+ | | | | +----------------------------+----------------------------------------------------------+--------------------------+ |log(), logf(), logl() | | MT-Safe | +----------------------------+----------------------------------------------------------+--------------------------+ C11, POSIX.1-2008. C99, POSIX.1-2001. , double, SVr4, 4.3BSD, C89. glibc 2.5 log() NaN (FE_INVALID). cbrt(3), clog(3), log10(3), log1p(3), log2(3), sqrt(3) () Artyom Kunyov , Azamat Hackimov , Dmitry Bolkhovskikh , Katrin Kutepova , Konstantin Shvaykovskiy , Yuri Kozlov ; GNU (GNU General Public License - GPL, 3 ) , - . - , , () () () . Linux man-pages 6.18 8 2026 . log(3)