How do I access command-line arguments?

The command-line arguments are passed to a script in the global table arg. The actual arguments are arg[i] where i runs from 1 to #arg - or you could use ipairs. arg[0] is the name of the script, as it was called; arg[-1] is the name of the Lua executable used.

> lua arg.lua one "two three"
1 one
2 two three
-1 lua
0 arg.lua

(where 'arg.lua' is just 'for k,v in pairs(arg) do print(k,v) end`)

You can use arg[0] to find out where your script is installed; if it's an absolute path, then use that, otherwise use the current directory plus the path given.

It is possible to make a directly executable script under Unix by making the first line '#!/usr/local/bin/lua' or '#!/usr/bin/env lua' and making the script itself executable. On Windows you can achieve this by adding ';.lua' to the PATHEXT environment variable and make execution the default action when opening Lua files.

Note that arg is set by the standard interpreter; if your C/C++ program launches a script with luaL_dofile then arg will be nil, unless you specifically set it.