(*  Title:      Pure/Concurrent/bash.ML

     Author:     Makarius

 GNU bash processes, with propagation of interrupts.

 *)

 val bash_output = uninterruptible (fn restore_attributes => fn script =>

   let

     datatype result = Wait | Signal | Result of int;

     val result = Synchronized.var "bash_result" Wait;

     val id = serial_string ();

     val script_path = File.tmp_path (Path.basic ("bash_script" ^ id));

     val output_path = File.tmp_path (Path.basic ("bash_output" ^ id));

     val pid_path = File.tmp_path (Path.basic ("bash_pid" ^ id));

     val system_thread =

       Simple_Thread.fork false (fn () =>

         Multithreading.with_attributes Multithreading.private_interrupts (fn _ =>

           let

             val _ = File.write script_path script;

             val status =

               OS.Process.system

                 ("exec \"$ISABELLE_HOME/lib/scripts/process\" group " ^

                   File.shell_path pid_path ^ " script \"exec bash " ^

                   File.shell_path script_path ^ " > " ^

                   File.shell_path output_path ^ "\"");

             val res =

               (case Posix.Process.fromStatus status of

                 Posix.Process.W_EXITED => Result 0

               | Posix.Process.W_EXITSTATUS 0wx82 => Signal

               | Posix.Process.W_EXITSTATUS w => Result (Word8.toInt w)

               | Posix.Process.W_SIGNALED s =>

                   if s = Posix.Signal.int then Signal

                   else Result (256 + LargeWord.toInt (Posix.Signal.toWord s))

               | Posix.Process.W_STOPPED s =>

                   Result (512 + LargeWord.toInt (Posix.Signal.toWord s)));

           in Synchronized.change result (K res) end

           handle _ (*sic*) => Synchronized.change result (fn Wait => Signal | res => res)));

     fun cleanup () =

      (Simple_Thread.interrupt system_thread;

       try File.rm script_path;

       try File.rm output_path;

       try File.rm pid_path);

     fun kill n =

       (case Int.fromString (File.read pid_path) of

         SOME pid =>

           Posix.Process.kill

             (Posix.Process.K_GROUP (Posix.Process.wordToPid (LargeWord.fromInt pid)),

               Posix.Signal.int)

       | NONE => ())

       handle OS.SysErr _ => ()

         | IO.Io _ => (OS.Process.sleep (seconds 0.1); if n > 0 then kill (n - 1) else ());

   in

     let

       (*proxy for interrupts*)

       val _ =

         restore_attributes (fn () =>

           Synchronized.guarded_access result (fn Wait => NONE | x => SOME ((), x))) ()

         handle exn => (if Exn.is_interrupt exn then kill 10 else (); reraise exn);

       val output = the_default "" (try File.read output_path);

       val rc = (case Synchronized.value result of Signal => Exn.interrupt () | Result rc => rc);

       val _ = cleanup ();

     in (output, rc) end

     handle exn => (cleanup (); reraise exn)

   end);