I am trying to writing into the file and reading the content from the file, I able to write into the file but I unable to read the contents from the file.
Tried Code:

-module(main).
-export([file_wr/1,file_wrt/2,file_rede/2]).

file_wr(Str) ->
  {ok,File} = file:open("input.txt",[write]),
  D = [[D] || D <- Str],
  file_wrt(File,D),
  file_rede(File,D),
  file:closeall(). 
file_wrt(File,[]) ->
    File;
file_wrt(File,[First | Last]) ->
 io:fwrite(File, "~s",[First]),
 file_wrt(File,Last).
file_rede(File,[]) -> 
  file:close(File),
  io:fwrite("\nCompleted\n");
file_rede(File,D) ->
  {ok,List} = file:open(File,[read]),
  {ok,Read} = file:read(List,1024*1024),
   case io:read(Read,"") of 
     eof ->
          file:close(File), D;
     Item ->
          file_rede(File,D ++ [Item])
    end.

And I modified the above code to the below mentioned that will writing/reading the contents into/from the file. To achieve this, I written the two modules (), the reading module is imported into the written module in the below code.
Code for Reading the Contents from the file:

-module(file_reading).
-export([reading/1,readlines/1,get_all_lines/2]).
reading(FileName) ->
 Lines =readlines(FileName),
 io:format("~s~n",[Lines]).
readlines(FileName) ->
    {ok, Device} = file:open(FileName, [read]),
    get_all_lines(Device, []).
get_all_lines(Device, Accum) ->
    case io:get_line(Device, " ") of
        eof  -> file:close(Device), Accum;
        Line -> get_all_lines(Device, Accum ++ [Line])
    end.

The above module is import into the writing module , it will be executing in single module for both writing and reading from the single file.
Code for Writing and reading the contents from the file:

**

-module(file_writing).
-export([start/1,file_wrt/2]).
-import(file_reading,[reading/1]). #Importing the reading from the file_reading module and I defined in the same main branch.
start(FileName) ->
 io:format("~nReading the contents to the given file line by line: ~s ~n",[FileName]),
 String = io:get_line("Enter a string: "),
 L = [[L] || L <- String ],
 file_wrt(FileName,L),
 file:close(FileName),
 io:format("~nPrinting the contents of the given file: ~s ~n ",[FileName]),
 file_reading:reading(FileName).
file_wrt(FileName,L) ->
 {ok, S} = file:open(FileName, [write,append]),
   lists:foreach(fun(X) -> io:fwrite(S, "~s",[X]) end, L),
    
    file:close(S).

**