How to continuously show os command output in erlang? - operating-system

Question

I need continuously show stdout/stderr from os command in erlang.
In ruby I can implement it with following code:
s1, s2 , s3, t = Open3.popen3('for %a in (1 2 3 4 5 6 7 8 9) do (echo message & sleep 2 ) 2>&1 ')
s2.each do |l|
puts l
end
it will show 'message\n message\n' in 'real time' - does not wait end of process.
I've tried os:cmd(..)
and
1> P5 = erlang:open_port({spawn, "ruby rtest.rb"}, [stderr_to_stdout, in, exit_s
tatus, binary,stream, {line, 255}]).
#Port<0.505>
2> receive {P5, Data} -> io:format("Data ~p~n",[Data]) end.
Data {data,{eol,<<>>}}
ok
but both of them wait end of process.
Are the any optional for continuously stdout reading in Erlang?
EDIT:
In other words I look for a popen (c/c++; proc_open(php) and etc) function in erlang
EDIT2
Code, that works on linux (tested on centos6.2). Thanks for vinod:
-module(test).
-export([run/0]).
run() ->
P5 = erlang:open_port({spawn, "sh test.sh"},
[stderr_to_stdout, in, exit_status,stream, {line, 255}]),
loop(P5).
loop(P) ->
receive{P, Data} ->
io:format("Data ~p~n",[Data]),
loop(P)
end.
Output:
10> c(test).
{ok,test}
11> test:run().
Data {data,{eol,"1"}}
Data {data,{eol,"2"}}
Data {data,{eol,"3"}}
Data {data,{eol,"4"}}
Data {data,{eol,"5"}}
Data {data,{eol,"6"}}
Data {data,{eol,"7"}}
Data {data,{eol,"8"}}
Data {data,{eol,"9"}}
Data {data,{eol,"10"}}
Data {exit_status,0}

Answer 1

If I understand correctly, you want to continue to execute your program in concurrent with the os command. In Erlang you can just spawn a process which does that and you can continue. For example
1> spawn(fun() ->
P5 = erlang:open_port({spawn, "ruby rtest.rb"},
[stderr_to_stdout, in, exit_status,
binary,stream, {line, 255}]),
receive {P5, Data} ->
io:format("Data ~p~n",[Data])
end
end).
<0.32.0>
2> 5+5.
10
3>
Better to write in a module so that you can understand it better.