Hi David,

Am Dienstag, 26. Mai 2020, 01:28:43 CEST schrieb David T. Lewis:
> Hi Martin,
>
> On Fri, May 22, 2020 at 10:35:08PM +0200, Martin Kuball wrote:
> > Hi David,
> >
> > I finally found a solution to my problem. Successfully converted 1300
> > images in a couple of minutes. The code I come up with is roughly the
> > following (using the wc program here as a proof of concept before
> > switching to tesseract and>
> > image data for the input):
> > | input output stdErr proc accessProtect res err |
> >
> > input := ExternalPipe nonBlockingPipe.
> > output := ExternalPipe blockingPipe.
> > stdErr := ExternalPipe nonBlockingPipe.
> > proc := ExternalOSProcess concreteClass
> >
> > 	programName: '/usr/bin/wc'
> > 	arguments: #('-w')
> > 	initialEnvironment: nil.
> >
> > proc initialStdIn: input reader.
> > proc initialStdOut: output writer.
> > proc initialStdErr: stdErr writer.
> > accessProtect := Semaphore forMutualExclusion.
> > accessProtect critical: [
> >
> > 	proc value.
> > 	input nextPutAll: 'this is a test'.
> > 	input closeWriter.
> > 	res := output upToEndOfFile.
> > 	err := stdErr upToEndOfFile
> >
> > ].
> > proc waitForTermination.
> > output close.
> > stdErr close.
> > proc exitStatus ~= 0
> >
> > 	ifTrue: [^ 'error ' , proc exitStatus , ': ' , err].
> > 	ifFalse: [^res]
>
> I'm glad it worked out for you!
>
> > Mybe it is possible to reuse more of your high-level code. But I wanted
> > low
> > overhead and complete control over the input and output streams.
>
> Indeed, it can be interesting to work with this at a lower level so you
> can see exactly what is going on.
>
> > By the way uninstalling an older version of OSProcess and installing the
> > new one left a OSProcess watcher with an ObsoleteUnixOSProcessAccessor
> > running.
> This does not surprise me. That would just be the child process watcher that
> was left running after removing all the OSProcess classes, so I guess you
> would have to terminate the old process in that case.

That's exactly what I did ;).

>
> > And a final question: If you want to get a deeper understanding of process
> > handling in squeak, what would you recomend to read? Is the blue book
> > still a good reference?
>
> I think we are talking about two different things here. In Smalltalk, a
> process is very lightweight, more like what you would call a thread in most
> operating systems today. The blue book descriptions are still very relevant.
> There have been some changes and improvements in Squeak over the years, but
> the basics would still be the same.

Sorry, my question really was a little bit ambigous. And it was about the
Smalltalk "internal" process model. Like class Semaphore. I still don't
understand why you use critical: method in many places.
Or e.g. I added a Delay for debugging purposes after starting the external
process. But that did not work. The process exited imediately with an error
that it could not read from stdIn.

>
> The "processes" in OSProcess are a different thing entirely. These refer to
> the processes of the underlying operating system. For an operating system
> like Unix (Linux) or Windows, these processes are heavier-weight, and they
> carry quite a lot of execution context in addition to the basic schedulable
> unit of execution.
>
> If you were to make a comparison, a Process in Squeak is like a "green
> thread" in typical operating system lingo.
>
> But to your question - yes I would start with the blue book, and then others
> on this list (notably Eliot Miranda) can give explanations of the finer
> points and the more recent chnages.
>
> Dave
>
> > Thanks again for your help and the great code.
> >
> > Martin
> >
> > Am Samstag, 16. Mai 2020, 00:13:19 CEST schrieb David T. Lewis:
> > > Hi Martin,
> > >
> > > On Fri, May 15, 2020 at 09:20:17PM +0200, Martin Kuball wrote:
> > > > Am Donnerstag, 14. Mai 2020, 23:27:59 CEST schrieb David T. Lewis:
> > > > > On Thu, May 14, 2020 at 09:37:26PM +0200, Martin Kuball wrote:
> > > > > > Hi!
> > > > > >
> > > > > > I'm trying to do some OCR from squeak using tesseract. I installed
> > > > > > OSProcess. So far so good. But I don't know what classes to use
> > > > > > for
> > > > > > stdIn
> > > > > > and stdOut. My>
> > > > > >
> > > > > > code would look something like this:
> > > > > > | proc stdIn stdOut d |
> > > > > >
> > > > > > stdIn := ???
> > > > > > stdOut := ???
> > > > > > proc := ExternalUnixOSProcess forkAndExec: '/usr/bin/tesseract'
> > > > > > arguments:
> > > > > > #('-' '-' '--dpi' '100') environment: nil descriptors: (Array
> > > > > > with:
> > > > > > stdIn
> > > > > > with: stdOut with: nil).
> > > > > > proc ifNil: [self class noAccessorAvailable].
> > > > > > d := Delay forMilliseconds: 50.
> > > > > > [proc runState == #complete] whileFalse: [d wait].
> > > > > > " and now read the text from stdOut..."
> > > > > >
> > >  > > > Can someone fill in the blanks or point me to code that does
> > >  > > > similar
> > > > > >
> > > > > > things? Thanks very much.
> > > > >
> > > > > Hi Martin,
> > > > >
> > > > > First, please also install CommandShell in addition to OSProcess.
> > > > > Get
> > > > > the
> > > > > latest versions of both OSProcess and CommandShell, regardless of
> > > > > the
> > > > > version of Squeak you are using. If you are using SqueakMap to load
> > > > > them,
> > > > > then please select the versions labelled "(head)".
> > > > >
> > > > > Start out by trying something like this:
> > > > >     OSProcess outputOf: 'tesseract - - --dpi 100'
> > > > >
> > > > > I'm not sure if this will do what you want but please give it a try,
> > > > > and if it does not work I'll try to give a better answer.
> > > > >
> > > > > This uses a couple of new methods that I added to OSPrecess
> > > > > recently,
> > > > > but have not mentioned until now. If it proves to be useful you, you
> > > > > will be the first :-)
> > > > >
> > > > > Assuming that it works, here is what will have happened:
> > > > >
> > > > > - The argument string is parsed into a unix-style command pipeline
> > > > >
> > > > > - The pipeline is all objects, with OS process proxies doing the
> > > > > work
> > > > >
> > > > > - When evaluated, and stderr result will show up in an error
> > > > > notifier
> > > > >
> > > > >   in your image (proceed though the notifier)
> > > > >
> > > > > - Command stdout is collected and answered as the result of
> > > > > #outputOf:
> > > > >
> > > > > I would recommend running this in a debugger so you can step through
> > > > > it and see what is going on.
> > > > >
> > > > > Dave
> > > >
> > > > Hi Dave,
> > > >
> > > > thanks for your answer. Acutally I did install CommandShell because I
> > > > thougth it might help me understand the usage of OSProcess. And maybe
> > > > it
> > > > will if I give it more time.
> > > >
> > > > So here is what I did: I configure the following repository:
> > > >
> > > > MCHttpRepository
> > > >
> > > > 	location: 'http://www.squeaksource.com/OSProcess'
> > > > 	user: ''
> > > > 	password: ''
> > > >
> > > > and installed OSProcess-Base dtl.71, OSProcess-AIO dlt.9 and
> > > > OSProcess-Unix
> > > > dtl.35. But I do not see any mention of a head label. So where did I
> > > > go
> > > > wrong?
> > >
> > > From the OSProcess repository, load OSProcess-dtl.118. From the
> > > CommandShell repository, load CommandShell-dtl.109. These are currently
> > > the most recent versions. Ignore the sub-packages such as
> > > "OSProcess-Unix", that is something I did to support Pharo (something
> > > of a fools errand if I may say so). All of the sub-packages are
> > > included in the full OSProcess and CommandShell packages.
> > >
> > > A shortcut to do this is:
> > > 	Installer ss project: 'OSProcess'; install: 'OSProcess'.
> > > 	Installer ss project: 'CommandShell'; install: 'CommandShell'.
> > >
> > > The "(head)" version labels in the SqueakMap package loader do the same
> > > thing, except for the alarming warning messages which you can safely
> > > ignore.> >
> > > > The command you suggested worked. At least if I provide the image to
> > > > tesseract as a file. I will go on with the debugger and try to find
> > > > out
> > > > how to feed the image data to stdIn.
> > >
> > > The basic Unix shell redirector operators #> and #< should work. For
> > >
> > > example, try evaluating this:
> > >    OSProcess outputOf: 'cat < /etc/services | edit'
> > >
> > > I am not familiar with tesseract, but you can probably use the same
> > > approach.
> > >
> > > Dave