anchor.diff:  
   -behaviour(gen_server).
   
  --export([exec/1]).
  +-export([exec/1, exec/2]).
   -export([syn_exec/1]).
   -export([stop/1]).
   -export([os_pid/1]).
  
positive.code: handle_cast(_Msg, State) ->
      {noreply, State}.
  
  handle_info({'EXIT',FromExecPid,ExitInfo}, S = #state{exec_pid = ExecPid}) when FromExecPid =:= ExecPid ->
      {stop, {shutdown, translate_status(ExitInfo)}, S}.
  
  
negative.code:      terminate/2,
       code_change/3]).
  
  -record(state, {owner, os_pid, exec_pid}).
  
  exec(Command) ->
      exec(Command, []).
  exec(Command, Options) ->
      gen_server:start_link(?MODULE, [Command, self(), Options], []).
  
  syn_exec(Command) ->
      case exec:run(Command, [sync, stdout]) of
  