login name to look up
Nullable!SystemUser — null if no such user exists.
Exception on unexpected errors from getpwnam_r.
import unit_threaded.assertions; auto root = getSystemUser("root"); root.isNull.shouldBeFalse; root.get.name.shouldEqual("root"); root.get.uid.shouldEqual(0); getSystemUser("this_user_definitely_does_not_exist_xyzzy").isNull.shouldBeTrue;
Look up a system user by name.