I would like to obtains input parameters for the function gamma(a,b), where a is the gamma shape parameter and b is the scale parameter. I would like to obtain these parameters from a glm model, e.g.,

glm y1 x1 x2 x3, family(gamma) link(log)

It seems the scale parameter is reported in the standard output if I am understanding correctly. But I am not sure how to go about calculated the shape parameter. Any help is greatly appreciated.