There's no doubt that what kg4wsv suggested in indeed very clever, powerful and cool 
However it is more flexible to have the arduino signal which button was pressed and nothing else, that way you can move the arduino from a Linux PC to a Solaris box or BSD system or a Mac or even a win****** PC without having to make any modifications to the arduino itself, each host system would have its own version of the scripting language with its command mapping
If you use a cross platform language your code would be 99% + identical on all Unix systems, even on win****** the code changes would be fairly minor
In response to that_chap about AppleScript, I am not familiar with it, but Linux has bash which is the default shell on most distributions, in addition to the command line shell Linux also has a variety of scripting languages such as the ones mentioned earlier ( Perl, Python, PHP, Ruby, etc )
Other shells like ksh, tcsh, csh are also available
These shells are also available on BSD and most Unix systems
Since MacOS X is based on BSD it has inherited some of this functionality as well
Linux and Unix shells can also run on win****** via cygwin