troubleshooting question

Greetings,

I copied this simple example from the Beginners page:

OSProcess thisOSProcess stdOut nextPutAll: 'Hello World' 

Before running it, I did install the OSProcess OSProcess Pluggin packages.

But I get an MessageNotUnderstood error browser. But I can't seem to figure out why stdOut is not understanding nextPutAll:

Thanks for help.

Tom Keller, Ph.D.

[hidden email]

503-494-2442

6339b Basic Science Bldg

<a href="http://www.ohsu.edu/research/core" title="http://www.ohsu.edu/research/core" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)"> http://www.ohsu.edu/research/core

_______________________________________________
Beginners mailing list
[hidden email]
<a onclick="return top.js.OpenExtLink(window,event,this)" href="http://lists.squeakfoundation.org/mailman/listinfo/beginners" target="_blank">http://lists.squeakfoundation.org/mailman/listinfo/beginners

On Tue, Jul 18, 2006 at 11:19:56AM -0700, Thomas J Keller wrote:
> Greetings,
> I copied this simple example from the Beginners page:
> OSProcess thisOSProcess stdOut nextPutAll: 'Hello World'
>
> Before running it, I did install the OSProcess OSProcess Pluggin
> packages.
>
> But I get an MessageNotUnderstood error browser. But I can't seem to
> figure out why stdOut is not understanding nextPutAll:

Hi Tom,

OSProcess does not work on all platforms. If you are using Linux (or
Mac OS/X with the less common Unix VM), the example should work. But
if you are using Windows, it would not work unless you build your own
custom VM and plugins (not what you had in mind, I'm sure).

Almost everything in Squeak works identically on all platforms, but
OSProcess is an exception to this rule. It is intended to provide
platform-specific extensions, and it works differently (or not at
all) on different platforms.

As for troubleshooting, try playing around with the Squeak debugger.
When you saw the "MessageNotUnderstood browser", you were seeing
the debugger. Open in up and explore a little, and you'll be able
learn a lot about problems like this one. You can also open a debugger
right away and use it to step slowly through a problem to see where
it goes wrong. For you example, try evaluating this in your workspace:

  self halt.
  OSProcess thisOSProcess stdOut nextPutAll: 'hello world'

Hope this helps a little,
Dave


_______________________________________________
Beginners mailing list
[hidden email]
http://lists.squeakfoundation.org/mailman/listinfo/beginners

On Thu, Jul 20, 2006 at 11:03:11AM -0700, Thomas Keller wrote:
> Perhaps this is the problem?
> When I ran this in a worksheet:
> a _ OSProcess thisOSProcess stdOut.
> Transcript show: a
>
> show: returned "nil"
> So nextPutAll: has no where to print to?

Yes, that's exactly right. Your system cannot find its standard output
(because it does not have the necessary platform-specific OSProcess
plugin installed), so its standard output is nil. And nil is really
an object, like everything else in Squeak. When you send the message
#nextPutAll: to the nil object, the nil object responds by throwing
a MessageNotUnderstood error (MessageNotUnderstood is also an object,
you can find in in a browser if you like). The default response to
a MessageNotUnderstood error is to open a debugger, which lets you
poke around and figure out what went wrong.

> So my next question is how do I find the systems STDOUT pid?

There are several ways to answer this, so let me start by taking
the question literally. With the VM and plugins you are currently
using, you cannot see either the pid of the process that Squeak
is running in, or the identity of the STDOUT steam.  But not to
worry, you probably don't really need either of these.

It may seem odd at first, but try to think of Squeak as a self
contained object environment, rather than as a program that does
I/O to STDOUT and to files. The Transcript usually plays the role
of STDOUT in the sense that you can evaluate things and show the
result on the Transcript. Even more commonly, you can evaluate
an expression (which may invoke some computation of arbitrary
complexity), and "inspect it" to see the results directly.

But back to being literal. If you really want to see the pid
of the current Squeak process, and to have access to the
STDOUT, STDIN, and STDERR streams, then you need to run your
Squeak image with a virtual machine that has the OSProcess plugin
extension. You can get this from http://www.squeakvm.org/unix/.
If you install the MacOSX VM from this page, it will provide
the OSProcess plugin, and if you run your Squeak image with
this VM, it should do exactly what you want.

I'm glad that you are interested in OSProcess, because I wrote
it. But what I really hope is that you will quickly discover
that OSProcess is completely unnecessary for almost everything
you will want to do in Squeak. In my own experience, the more I
became comfortable with Squeak, the less I worried about traditional
file I/O and the like. It's nice to be able to do that stuff
(hence the OSProcess extensions), but it's rarely needed once
you get comfortable with the Squeak environment.

Dave

_______________________________________________
Beginners mailing list
[hidden email]
http://lists.squeakfoundation.org/mailman/listinfo/beginners