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clog - Man Page

natural logarithm of a complex number


Math library (libm, -lm)


#include <complex.h>

double complex clog(double complex z);
float complex clogf(float complex z);
long double complex clogl(long double complex z);


These functions calculate the complex natural logarithm of z, with a branch cut along the negative real axis.

The logarithm clog() is the inverse function of the exponential cexp(3). Thus, if y = clog(z), then z = cexp(y). The imaginary part of y is chosen in the interval [-pi,pi].

One has:

clog(z) = log(cabs(z)) + I * carg(z)

Note that z close to zero will cause an overflow.


For an explanation of the terms used in this section, see attributes(7).

clog(), clogf(), clogl()Thread safetyMT-Safe


C11, POSIX.1-2008.


glibc 2.1. C99, POSIX.1-2001.

See Also

cabs(3), cexp(3), clog10(3), clog2(3), complex(7)

Referenced By

cacos(3), casin(3), catan(3), cexp(3), clog10(3), clog2(3), complex(7), log(3).

The man pages clogf(3) and clogl(3) are aliases of clog(3).

2024-05-02 Linux man-pages 6.9.1