L1317 - Format Error

Error

  main() ->
  io:format("These are two arguments: ~p, ~p", [only_one]).
%%                                             ^^^^^^^^^^ warning: the format string requires an argument list with 2 arguments, but the argument list contains only 1 argument

Explanation

The warning occurs when the format string and the actual list of parameters in a io:format/2, io_lib:format/2 or equivalent function are inconsistent. In the example above, this happens because the format string (the first of the two arguments to the io:format/2 function) contains two control sequences for formatting (~p), but the list of arguments only contains one element.

To learn more about formatting strings and control sequences, please refer to the official documentation for the io:fwrite/3 function.