CONJ(3) Linux Programmer's Manual CONJ(3)

conj, conjf, conjl - calculate the complex conjugate

#include <complex.h>
double complex conj(double complex z);
float complex conjf(float complex z);
long double complex conjl(long double complex z);
Link with -lm.

These functions return the complex conjugate value of z. That is the value obtained by changing the sign of the imaginary part.
One has:
    cabs(z) = csqrt(z * conj(z))

These functions first appeared in glibc in version 2.1.

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
conj (), conjf (), conjl () Thread safety MT-Safe

C99, POSIX.1-2001, POSIX.1-2008.

cabs(3), csqrt(3), complex(7)