CODEWITHSUNDEEP
erlang
user2979663
user2979663

Reputation: 15

I/O with Erlang, trying to get input file into list

-module(test).
-export([run/1]).

open_file(FileName, Mode) ->
    {ok, Device} = file:open(FileName, [Mode, binary]),    Device.

close_file(Device) ->
    ok = file:close(Device).

read(File) ->
    case file:read_line(File) of
        {ok, Data} -> [Data | read(File)];
        eof        -> []
    end.
run(InputFileName) ->
    Device = open_file(InputFileName, read),
    Data = read(Device),
    [First |TheRest] = Data,
    io:format("First line is ~p ~n", [First]),
    close_file(Device).

The original file 

d1  and is  program program the
d2  a   apply   copyleft    free    free    freedom
d3  copyleft    copyleft    share   share   users
d4  released    software    works
d5  licenses    licenses    licenses    licenses    licenses    software
d8  apply

somehow turns into

50> test:run("input.txt").
First line is <<"d1\tand\tis\tprogram\tprogram\tthe\n">> 
ok

Is this a special way of representing a list? or do I need to use kind of module to convert the read into a list?

My ultimate goal is to make a key pair with a list:

{d1 [and is program program the]}

Thank you!

Upvotes: 1

Views: 330

Answers (1)

Steve Vinoski
Steve Vinoski

Reputation: 20024

The data you're reading from your file is represented as a binary, rather than a string, because you're specifying binary mode when you open the file:

{ok, Device} = file:open(FileName, [Mode, binary]), Device.

If you change this to:

{ok, Device} = file:open(FileName, [Mode]), Device.

your result becomes:

First line is "d1 and is program program the\n"

To get the ultimate result, change your read/1 function to this:

read(File) ->
    case file:read_line(File) of
        {ok, Data} ->
            [First|Rest] = string:tokens(Data, " \t\n"),
            [{First,string:join(Rest, "\t")} | read(File)];
        eof -> []
    end.

With this change, your program prints:

First line is {"d1","and\tis\tprogram\tprogram\tthe"}

where the second element is a string in which the tokens are tab-separated as in your original data. If you want the first element, "d1", to instead be an atom d1 (I can't tell for sure from your question if this is what you want), you can convert it with list_to_atom/1.

Upvotes: 1

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