by H.G.Muller » 29 Apr 2014, 16:56
If you did "sudo make install" then the GNU Chess you compiled should have become the default GNU Chess on your system. It is not really true that this replaced the original GNU Chess. Debian uses the convention that binary packages from the repositories are in installed in /usr (in this case /usr/games/guchess), while software you compile from source is installed in /usr/local (in this case /usr/local/games/gnuchess). But because /usr/local/games is in your shell's search path before /usr/games, the things you installed from source 'eclipse' the corresponding files that came with the distro. So as long as your self-compiled stuff is there, the original stuff might as well have been deleted. But when you remove your self-compiled stuff, the original stuff becomes active again.
This only holds if you installed, because only 'make install' ill move the binaries and their data files to the place where they belong. If you topped at 'make', the gnuchess binary will still sit in the directory here you 'maked' it. Typing 'gnuchess' at the command prompt (and also when XBoard issues it) would then invoke the original version of GNU Chess, as /usr/games is searched before the current directory, and the latter is only searched when you would type ./gnuchess. (And if you are no longer in the directory where gnuchess is, it could not be found at all, unless you specify the path to it.)
Note that not all engines might be compliant with these conventions, but since GNU Chess is coming from the Ubuntu repositories, I suppose it is. (But be careful with engines that are basically just hacked Windows versions; they are often made by people that don't know where one should put files on Linux, and could put them in the strangest places.)
I don't know what you have to do to make GNU Chess use its own book, and where it looks for it by default. (One would expect something like /usr/local/share/games/gnuchess/*.bin .) As I said, I never used GNU Chess 6.
Note that the default engine of XBoard is not gnuchess, but fairymax. But this merely means that giving a plain "xboard"command is the same as typing "xboard -fcp fairymax -scp fairymax". XBoard only knows the default engine by name, and issues that name a a command, not making any attempt to control what the system does with it. So it is not like XBoard has some secret path to the default engine that would make it use anything else than what you would get when you typed 'fairymax' at the command prompt in a terminal window.
