How determine or visualize level curves Let $f:\mathbb{C}\to\mathbb{C}$ given for $f(z)=\int_0^z \frac{1-e^t}{t} dt-\ln z$ and put $g(x,y)=\text{Re}(f(z))$. While using the computer, how to determine the curve $g(x,y)=0$?
Thanks for the help.

Using Mathematica:
ContourPlot[With[{z = x + I y},
                  Re[EulerGamma - ExpIntegralEi[z]]] == 0,
             {x, -20, 20}, {y, -20, 20}]


