This is true of shell built-ins for eg. test too. The solution is to use the full path if you want to use the program, not the shell built-in. In this case, "

This is true of shell built-ins for eg. test too. The solution is to use the full path if you want to use the program, not the shell built-in. In this case, "/usr/bin/open" not "open" will get you the macOS utility. If you get sick of doing that, create a shell alias.