in reply to Re^4: Perl Background processes in Windows
in thread Perl Background processes in Windows

Consider looking at perlop to see what -x does. Also, if it "always fails" (and you're interested in learning why), consider posting full code.

Please note that dir and date are shell builtins in cmd.exe and thus never pass -x, because they are not programs that can be run. Also note that -x expects the full path to an executable and does not search $ENV{PATH}. Whether that is desired or not in the context of the above program, I don't know. Update: As the argument is passed to Win32::Process::Create(...), it makes sense to have a fully specified path, because that's what Win32::Process::Create() likely wants.

>perl -wle "print $_, -x $_ ? ' yes':' no' for @ARGV" cmd.exe c:\WINDO
+WS\system32\cmd.exe
cmd.exe no
c:\WINDOWS\system32\cmd.exe yes

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As to using system or backticks, these do not launch a background process. Which seems to be the purpose of the code under discussion. Actually, perlport points out system(1, ...) for launching a process in the background under Windows and OS/2.

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Re^6: Perl Background processes in Windows
by Anonymous Monk on Jan 31, 2012 at 10:32 UTC

    Proc::Background - Generic interface to Unix and Win32 background 

            use Proc::Background;
        timeout_system($seconds, $command, $arg1);
        timeout_system($seconds, "$command $arg1");

        my $proc1 = Proc::Background->new($command, $arg1, $arg2);
        my $proc2 = Proc::Background->new("$command $arg1 1>&2");
        $proc1->alive;
        $proc1->die;
        $proc1->wait;
        my $time1 = $proc1->start_time;
        my $time2 = $proc1->end_time;

        # Add an option to kill the process with die when the variable
+ is
        # DETROYed.
        my $opts  = {'die_upon_destroy' => 1};
        my $proc3 = Proc::Background->new($opts, $command, $arg1, $arg
+2);
        $proc3    = undef;

    [download]
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[d/l]
      Thanks very much for your help and information. With this info I could solve my issues rapidly. I rebuild the example of Peter Dragon for my usage: 
      sub start_child
{ my $Cmd        = $_[0];
  my $CmdOptions = $_[1];
  my $ChildProc;
  my $ChildPid;

  die "cannot execute cmd: $Cmd" unless (-x "$Cmd");
  require Win32::Process;
  Win32::Process::Create($ChildProc, $Cmd, $CmdOptions, 0, 0, ".") || 
+confess "Could not spawn child: $!";
  $ChildPid = $ChildProc->GetProcessID();

  # catch early child exit, e.g. if program path is incorrect
  sleep(1.0);
  POSIX::waitpid(-1, POSIX::WNOHANG()); # clean up any defunct child p
+rocess
  if (kill(0,$ChildPid))
  { print "Started child process id $ChildPid\n";
  }
  else
  { warn "Child process exited quickly: $Cmd: process $ChildPid";
  }
  return $ChildPid;
}


$ChildPid = start_child($Cmd1, $Cmd1Options);
sleep(5.0);
$ChildPid = start_child($Cmd2, $Cmd2Options);

      [download]
      At the moment I stop the childs by TASKKILL /F /PID of the commands I've started. Not the nicest solution, better to do it with interrupts, but I haven't read that part of the Perl cookbook yet ;)
[reply]
[d/l]

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