Platform Detection

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• Environment variables and io.popen with commands like 'uname' can help identify a system. See [LuaRocks cfg.lua] and [1].
• [package.config] (in 5.2.0-alpha and undocumented in 5.1) provides information like directory separators.
• Lua/APR [platform_get] returns 'UNIX', 'WIN32', 'NETWARE', or 'OS2'.
• Lua bytecode can be platform dependent. Parsing the header of bytecode returned by string.dump therefore can provide information such as endianness, sizeof(int), sizeof(size_t), sizeof(lua_Number), and whether floating point is supported. See [A No-Frills Introduction to the Lua 5.1 VM]. However, not all LuaImplementations implement the standard Lua bytecode format.

Note: some things can be tricky like Cygwin, which is like a *nix emulator on Windows. For portability purposes, Cygwin is mainly considered *nix, but it has some Windows features.