How to write a file in Lua?

Question

I just want to write a file to somewhere. Here is my code:

file = io.open("test.txt", "w")
file:write("Hello World")
file:close()

but the app crashes at the first line with:

attempt to call field 'open' (a nil value)

Even trying with the Lua online console keeps up the same error.

EDITED: Here is my screenshot of the console

Answer 1

Try this code to dump the keys of io:

for k in next,io do
  print(k)
end

Lua online outputs:

write

Which makes sense when you think about it:

Sandboxing works by restricting what can be done, including removal of unsafe functions.