The Scripting manual mentions that you can now read and write to files without size limitations in scripts.
From, Scripting Examples.
[/lua "local f=assert(io.open('/test.txt', 'w+')); f:write(newContent); f:close()"];

All I'm getting "bad command name"
I'm using both,
4.11 on a RB750
4.50 on X86 Device

Both are doing the same, Any Suggestions??

Read that manual again, LUA is not yet working. We are planning to integrate it in future versions.