Erlang - Open file read line delete line and save - concurrency

Question

I need to open a file, read the line, do some thing, delete that line save, open again the same file and continue with the rest
so far i have this code ..
1 -module(setup_data).
2 -export([for_each_line_in_file/1]).
3
4 for_each_line_in_file(Name) ->
5 {ok, Device} = file:open(Name, [read]),
6 for_each_line(Device).
7
8 for_each_line(Device) ->
9 case io:get_line(Device, "") of
10 eof -> file:close(Device);
11 Line ->
12 do_something(Line)
13 for_each_line(Device)
14 end.
So I want something like
1 -module(setup_data).
2 -export([for_each_line_in_file/1]).
3
4 for_each_line_in_file(Name) ->
4
6 for_each_line(Name).
7
8 for_each_line(Device) ->
9 {ok, Device} = file:open(Name, [read]),
9 case io:get_line(Device, "") of
10 eof -> file:close(Device);
11 Line ->
12 io:format("LINE : ...... ~p~n",[Line]),
23
43 /DELETE THAT CURRENT LINE AND SAVE?
33 file:close(Device)
13 for_each_line(Name)
14 end.

Answer 1

To elaborate on Armon comment:
In server fault q&a site, there was a post about how fast certain operations are. Disk seek for the first line in your file takes 10ms, while reading 1Mb of sequential data lasts 30ms. If your file has 300 lines, your solutions would work 10 times slower and if it has 3000 lines, it would be 100 times slower than reading 1Mb od data.
In this situation, read entire file to memory as a binary, do what you need to do with the lines and finally save the file again. You can distribute work between processes, but I wouldn't bother, because accessing disk is probably the longest operation in your code.