How to read the contents of a file In Erlang?

erlang

Solution

file:read_file/1 is what you are looking for. Just for teaching purpose, `Accum ++ [Line]` is bad practice. Problem is that left argument of `++` is copied and right is used as is. In your code you will copy bigger and bigger part in each iteration. Solution is `lists:reverse(Line,Accum)` and than return `lists:reverse(Accum)` in your `eof` branch (Or `[Line|Accum]` and `lists:append(lists:reverse(Accum))` at the `eof` or use binary which have better append operation or ...). Another way is not using tail recursive function which is not so bad as seems at first time according to Myth: Tail-recursive functions are MUCH faster than recursive functions.

So your `readlines/1` function should look like

readlines(FileName) ->
    {ok, Device} = file:open(FileName, [read]),
    try get_all_lines(Device)
      after file:close(Device)
    end.

get_all_lines(Device) ->
    case io:get_line(Device, "") of
        eof  -> [];
        Line -> Line ++ get_all_lines(Device)
    end.

Problem

Original source