[GHC] #8844: Pseudo terminal and process-1.2.0.0

4 Mar 2014

      #8844: Pseudo terminal and process-1.2.0.0
-------------------------------------+-------------------------------------
       Reporter:  ksamborski         |             Owner:
           Type:  feature request    |            Status:  new
       Priority:  normal             |         Milestone:
      Component:  libraries/process  |           Version:  7.6.3
       Keywords:  pty                |  Operating System:  Unknown/Multiple
   Architecture:  Unknown/Multiple   |   Type of failure:  None/Unknown
     Difficulty:  Unknown            |         Test Case:
     Blocked By:                     |          Blocking:
Related Tickets:                     |
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 Hello,

 I'm writing simple app which execute process and communicate with it
 via pseudo terminal. Here is some sample code:

 import System.Posix.Terminal
 import System.Process

 main = do
   (master, slave) <- openPseudoTerminal
   hslave <- fdToHandle slave
   hSetBuffering hslave NoBuffering
   (_,_,_,ph) <- createProcess (shell "mc"){ env = Just [("TERM", "xterm")]
                                           , std_in = UseHandle hslave
                                           , std_out = UseHandle hslave
                                           , std_err = UseHandle hslave
                                           , close_fds = True
                                           }
   forkIO $ readTerm master -- my function which reads output from process
   waitForProcess ph

 The problem is that mc still wants some input from stdin but not
 from slave terminal.
 But when I changed function runIteractiveProcess from runProcess.c like
 this:

 ...
         /* Reset the SIGINT/SIGQUIT signal handlers in the child, if
 requested
          */
         if (reset_int_quit_handlers) {
             struct sigaction dfl;
             (void)sigemptyset(&dfl.sa_
 mask);
             dfl.sa_flags = 0;
             dfl.sa_handler = SIG_DFL;
             (void)sigaction(SIGINT,  &dfl, NULL);
             (void)sigaction(SIGQUIT, &dfl, NULL);
         }

 /********************************************************************************/
         setsid(); //Make the current process a new session leader
         ioctl(0, TIOCSCTTY, 1); //As the child is a session leader,
 set the controlling terminal to be the slave side of the PTY
 /********************************************************************************/
         /* the child */
         if (environment) {
             // XXX Check result
             execvpe(args[0], args, environment);
         } else {
             // XXX Check result
             execvp(args[0], args);
         }

         childFailed(forkCommunicationFds[1], forkExecFailed);
 ...

 it worked as expected, I'm not proposing patch or solution but is there
 any chance to add support for pseudo terminals in the process library?
 Maybe just add another record field in CreateProcess like pty :: Bool and
 then call these two additional instructions in runIteractiveProcess?

 Best regards,
 Karol Samborski

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8844
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