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Understanding SB-EXT:RUN-PROCESS
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Josef Wolf  
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 More options Mar 23 2012, 6:14 am
Newsgroups: comp.lang.lisp
From: Josef Wolf <j...@raven.inka.de>
Date: Fri, 23 Mar 2012 10:14:53 +0000 (UTC)
Local: Fri, Mar 23 2012 6:14 am
Subject: Understanding SB-EXT:RUN-PROCESS
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Hello,

I am trying to send some output to the printer. So I tried this:

 (let ((proc (sb-ext:run-program "a2ps" '()
                                 :search t
                                 :input :stream
                                 :output nil)))
   (format (sb-ext:process-input proc) "huhu~%")
   (sb-ext:process-close proc))

But somehow, SB-EXT:PROCESS-CLOSE seems to be ignored, and a2ps hangs
indefinitely, trying to read more input from its stdin. Does anybody have any
idea what I might be missing here?


 
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Nicolas Neuss  
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 More options Mar 23 2012, 9:54 am
Newsgroups: comp.lang.lisp
From: Nicolas Neuss <lastn...@scipolis.de>
Date: Fri, 23 Mar 2012 14:54:16 +0100
Local: Fri, Mar 23 2012 9:54 am
Subject: Re: Understanding SB-EXT:RUN-PROCESS
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Josef Wolf <j...@raven.inka.de> writes:
> Hello,

> I am trying to send some output to the printer. So I tried this:

>  (let ((proc (sb-ext:run-program "a2ps" '()
>                                  :search t
>                                  :input :stream
>                                  :output nil)))
>    (format (sb-ext:process-input proc) "huhu~%")
>    (sb-ext:process-close proc))

> But somehow, SB-EXT:PROCESS-CLOSE seems to be ignored, and a2ps hangs
> indefinitely, trying to read more input from its stdin. Does anybody have any
> idea what I might be missing here?

This works for me:

(let* ((process (sb-ext:run-program
                 "/bin/cat" '()
                 :wait nil :input :stream :output :stream))
       (input (sb-ext:process-input process))
       (output (sb-ext:process-output process)))
  (write-line "Hello" input)
  (force-output input)
  (print (read-line output))
  (close input)
  (close output))

(Maybe the missing FORCE-OUTPUT or the missing :wait nil is your problem?)

Nicolas


 
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Josef Wolf  
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 More options Mar 26 2012, 10:55 am
Newsgroups: comp.lang.lisp
From: Josef Wolf <j...@raven.inka.de>
Date: Mon, 26 Mar 2012 14:55:41 +0000 (UTC)
Local: Mon, Mar 26 2012 10:55 am
Subject: Re: Understanding SB-EXT:RUN-PROCESS
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On 2012-03-23, Nicolas Neuss <lastn...@scipolis.de> wrote:

> (let* ((process (sb-ext:run-program
>                  "/bin/cat" '()
>                  :wait nil :input :stream :output :stream))
>        (input (sb-ext:process-input process))
>        (output (sb-ext:process-output process)))
>   (write-line "Hello" input)
>   (force-output input)
>   (print (read-line output))
>   (close input)
>   (close output))

Thanks for the hint, Nicolas. That helped me to get closer to the
problem. Please see below.

> (Maybe the missing FORCE-OUTPUT or the missing :wait nil is your problem?)

No, the missing FORCE-OUTPUT don't seem to be the problem. In addition,
PROCESS-CLOSE shold call FORCE-OUTPUT before closing, IMHO.

The real problem seems to be a little bit more subtle. First thing is, I need
to add

  :wait nil

to the lambda-list. (well reading the docs helps. Sorry, my fault )

Now comes the subtle thing: Once RUN-PROGRAM is called without
the :WAIT NIL parameter, further calls to RUN-PROGRAM will no longer close the
streams properly, regardless whether :WAIT NIL parameter is included in those
later calls or not. The same holds true if I ever call SB-EXT:PROCESS-WAIT to
collect zombies. I need to quit the sbcl instance and start another one to get
it working again.

Might this be a bug in sbcl-1.0.55? Or is it related to SLIME?


 
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