gmtset and gmtget are executables provided by old GMT4. Since GMT5, you should use gmt set and gmt get instead. As for gmtpath and gmtlist, they are not GMT commands.
gmtpath and gmtlist etc are old GMT3 commands that survived into GMT4 but was dropped in GMT5. It you need these ancient tools you might as well install the terminal release of GMT 4.5.18.