If you could put [code] tags around that code, it would be a lot easier to read and/or examine. But from the looks of it, it's checking file gdm.conf for strings "greeter=" and "welcome=", and giving them values, and putting the finished product into a new file, and finally moving that new file to gdm.conf. Last, it does some `pkgcheck` thing that I don't recognize.
As far as "what commands available", please tell us (A) what Linux (or other) distro this question applies to, and (B), which settings are you referring to?? You just want to know if the changes were made? Try this:
shell# cat /etc/X11/gdm/gdm.conf
and you should see something more or less like:
Welcome=Authorized uses only!\nAll activity may be monitored
And to see if it works, log in using Gnome