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Groups > comp.lang.java.programmer > #31825

Re: Getting results of command execution

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On Wednesday, June 17, 2015 at 6:28:51 PM UTC-7, Jeff Higgins wrote:
> On 06/17/2015 05:57 PM, FredK wrote:
> > On Wednesday, June 17, 2015 at 2:14:45 PM UTC-7, Eric Sosman wrote:
> >> On 6/17/2015 4:56 PM, FredK wrote:
> >>> I want to execute a set of commands and get the results. So I start with,
> >>> on Unix;
> >>>     process P = Runtime.getRuntime().exec("commandA; commandB");
> >>>
> >>> or on Windows
> >>>     process P = Runtime.getRuntime().exec("commandA & commandB");
> >>>
> >>> How do I get the results of the output AND error output in the order they are created?
> >>>
> >>> If I use this type of coding:
> >>> [...]
> >>> I get all of the stdout, followed by all of the stderr. But suppose commandA writes some output, then some errors, then more outputs, etc. I want to retrieve them in that order.
> >>
> >>       You could try using a ProcessBuilder to set up your Process, and
> >> use its redirectErrorStream() method to merge stdout and stderr before
> >> calling start().  But even then, you'll be at the mercy of whatever
> >> buffering takes place in the external process itself: If that process
> >> holds on to stdout data until it's got a bufferload, but emits stderr
> >> data right away (this is the default behavior for many C programs),
> >> the mingled data will be temporally scrambled no matter what you do
> >> on the receiving side.
> >>
> >>
> > I'm not sure I can accomplish what I want;
> 
> I'm sure that you're clear on what you want to accomplish
> but so far you haven't made it clear to me. It sounds as if
> you want to plant a Java process between a user and his CLI
> (sh, cmd.exe, ...) or perhaps replace it?
> 
> <http://labs.neohapsis.com/2008/04/17/connect-back-shell-literally/>
> 
> > I haven't been able to find anything that will let me execute multiple commands in the same invocation.
> >
> > I want to pass along user commands to be executed, and there might be a "cd" imbedded in the string, or setting some environment variables, or any of a multitude of things that cause one command to depend on the results of some previous command(s), so it I can't just execute each command in a separate process.
> >

The requirement is essentially that I want to include a panel in my program that acts like a shell. So throughout the lifetime of the program, in addition to interacting with the program the user can also use it as if it were a shell - kind of like a Unix xterm, with additional capabilities. For example, the user could type "ls", then point to a file name, right-click on it and it would open up an editor for that file (based on what kind of file it is), or if it is the name of a directory, cd to that directory and possibly execute ls in that directory. Typing "<Ctrl>+U" would execute "cd ..;pwd;ls", plus other features.

I have written something like this in C using Motif, and it works fine - I just fork at the beginning and the child becomes a shell, and I redirect the pipes such that I have access to the shell's input, output, and error streams.

But I don't know how to do this in Java.
-- 
Fred K

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Getting results of command execution FredK <fred.l.kleinschmidt@gmail.com> - 2015-06-17 13:56 -0700
  Re: Getting results of command execution Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-06-17 17:14 -0400
    Re: Getting results of command execution FredK <fred.l.kleinschmidt@gmail.com> - 2015-06-17 14:57 -0700
      Re: Getting results of command execution Martin Gregorie <martin@address-in-sig.invalid> - 2015-06-17 23:07 +0000
      Re: Getting results of command execution Jeff Higgins <jeff@invalid.invalid> - 2015-06-17 21:26 -0400
        Re: Getting results of command execution FredK <fred.l.kleinschmidt@gmail.com> - 2015-06-18 07:18 -0700
        Re: Getting results of command execution FredK <fred.l.kleinschmidt@gmail.com> - 2015-06-18 07:30 -0700
          Re: Getting results of command execution Jeff Higgins <jeff@invalid.invalid> - 2015-06-18 17:37 -0400
            Re: Getting results of command execution FredK <fred.l.kleinschmidt@gmail.com> - 2015-06-19 07:50 -0700
              Re: Getting results of command execution Jeff Higgins <jeff@invalid.invalid> - 2015-06-19 21:33 -0400
                Re: Getting results of command execution Jeff Higgins <jeff@invalid.invalid> - 2015-06-19 21:56 -0400
                Re: Getting results of command execution Jeff Higgins <jeff@invalid.invalid> - 2015-06-19 23:02 -0400
                Re: Getting results of command execution Jeff Higgins <jeff@invalid.invalid> - 2015-06-20 11:11 -0400
                Re: Getting results of command execution Jeff Higgins <jeff@invalid.invalid> - 2015-06-20 12:14 -0400
                Re: Getting results of command execution Jeff Higgins <jeff@invalid.invalid> - 2015-06-20 20:58 -0400
          Re: Getting results of command execution Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-06-19 11:01 -0400
      Re: Getting results of command execution Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-06-18 08:38 -0400
  Re: Getting results of command execution Jeff Higgins <jeff@invalid.invalid> - 2015-07-03 23:41 -0400

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