in reply to Re: TTY help
in thread TTY help

We don't have the IPC::Run either, but we do have IPC::Open3 but you said that won't work on windows...?

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Re^3: TTY help
by zentara (Cardinal) on Sep 17, 2008 at 16:12 UTC
    The problem on Win32, is that Win32 dosn't support "select" on pipes. IPC::Open3 uses pipes to connect to the command, while IPC::Run uses sockets( win32 select works on sockets). BUT, if you can figure out a way to NOT use select, and get the pipes flushed, you may be able to use it. Your main problem is output may be sitting in the pipe, but without $select->can_read, you won't know it. See Pipe Problem for some ideas.

    I don't use MSwindows, but there probably are hacks to get around the problem, like using sysread to read 1 byte at a time, until nothing is there, or see Non-blocking Reads from Pipe Filehandle

    You can use the SuperSearch here for many examples of using Open3, but remember, no select is available to you... so you need a workaround. See Perl/Tk App and Interprocess Communication. If you are using an event-loop system, you can setup a timer to repeatedly read the pipe until no bytes are there. Also see " perldoc -q 'capture STDERR' "


    I'm not really a human, but I play one on earth Remember How Lucky You Are
      How difficult do you think it would be to try and work with IPC::OPen3, especially since I'm a beginner? I really need to get this done this week and its seeming impossible for me to do since I don't have alot of Perl experience. Thanks for any help, J
        Using IPC::Open3, in it's simplest form, is very easy; BUT your windows command may be problem-prone.. all you can do is give it a quick try. Here is a very simple usage for doing a fast go/no-go test. See if you can print to your command, then collect all output. Uncomment the while(1){} code block, if you want to loop. Also note the sysread method, in case your <> read hangs. So give this a try, and report back your code and any problems you encounter.
        #!/usr/bin/perl use warnings; use strict; use IPC::Open3; my $pid = open3(\*WRITE, \*READ, \*ERROR,"your_command"); if( ! $pid ){ die "$!\n";} #my $pid = open3(\*WRITE, \*READ,0,"your_command"); #if \*ERROR is false, STDERR is sent to STDOUT #while(1){ print "Enter a string to evaluate\n"; chomp(my $query = <STDIN>); #send query to command print WRITE "$query\n"; #give small time to output select(undef,undef,undef,.5); #half second delay #get the answer from command chomp(my $answer = <READ>); print "$query = $answer\n"; # you may need something with sysread, if <READ> hangs # my $bytes_read = sysread(READ, my $buf, 1024); # print "$query = $buf\n"; #get the error from command chomp(my $error = <ERROR>); print "$query error = $error\n"; #} waitpid($pid, 1); # It is important to waitpid on your child process, # otherwise zombies could be created.

        I'm not really a human, but I play one on earth Remember How Lucky You Are
      Thanks I'll have a look at them. I suspect being a novice isn't gonna help me much :)
Re^3: TTY help
by Anonymous Monk on Oct 13, 2008 at 05:09 UTC
    I am also having the same problem. Any solution found, pleae share the same.