This is a boolean function which returns true if World of Warcraft is being run using the Linux client, it will return false with the Windows client under wine or OS X client run on other operating systems. Although there is no current official Linux client, the beta version of WoW had a Linux client, and the code retains a function to test for it.

eg

if IsLinuxClient() then
   s = "./myfile.xml"
else
   s = "myfile.xml"
end

[1]