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Re: getline timeout (revisited)

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On 19.04.2011 16:09, j.eh@mchsi.com wrote:
> In article <inmun6$lq1$1@speranza.aioe.org>, Janis Papanagnou wrote:
>> I've been currently looking for a timeout option for getline in
>> the context of an /inet/tcp/... socket communication with gawk.
>>
>> This topic had already been addressed here in c.l.a many many
>> years ago, as my google search showed, but I haven't found any
>> positive answers. Has there been something incorporated in gawk
>> or xgawk, meanwhile, or is the status unchanged. I suppose the
>> latter, but asking for a confirmation anyway.
> 
> [ Janis, I hit the wrong button. My intention was to post to
> the group, not to send a personal email. Sorry about that. ]

Don't worry; in my mailbox only spam isn't welcome. :-)

> 
> 
> I find the discussions in the old threads interesting, but I have
> a question. Let's assume we use PROCINFO to specify timeout like
> this:
> 
>      PROCINFO["/inet/tcp/..", "TIMEOUT"] = 1000 (ms)
> 
> and a value of 0 means the default behavior i.e. no timeout.

Yes.

> 
> Also, assume the existence of a builtin either in the gawk source
> or in a extension:
> 
>      readline("/inet/tcp/..")

Hmm.. - why a new function or builtin 'readline()' and not extending
the functionality of 'getline'? (Shouldn't conflict given the PROCINFO
approach.)

> 
> which other than being a function call behaves exactly like getline
> w.r.t. RS, RT and setting fields. We modify 'readline' to handle
> timeout anyway you think is suitable to serve our purpose. The question
> is then, if a script using 'readline' going to look any different
> than from the one that uses getline with exactly the same
> modifications.

I don't understand what you're saying above, and what you're aiming at.

> If possible, please consider providing the outline
> of such a script illustrating the usage of 'readline' or getline
> with timeout.

In my specific primitive application - which is by no means meant to be
a general example, covering all needs, or considering any corner cases -
it was just something like (simplified code)...

  BEGIN { P = "/inet/tcp/0/a.b.c.d/e" }
        { print some_funct($0) |&  P }
  /pat/ { P |& getline ; do_sth_w($0) }
  END   { close(P) }

which might, with timeouts, morph to something like...

  BEGIN { P = "/inet/tcp/0/a.b.c.d/e"
          PROCINFO[ P, "TIMEOUT"] = 1000
        }

        { print some_funct($0) |&  P }

  /pat/ { if( (P |& getline) > 0) do_sth_w($0)
          else print "Error:", PROCINFO[ P, "ERROR"]
        }

  END   { close(P) }


Using PROCINFO as a means to return the error is just an ad hoc thought
based on your timeout setting example. (So feel free to ignore it and
introduce something else.)

> To keep things uniform, assume we parse ERRNO to
> find out the cause of error. Not very gifted when it comes to writing
> awk scripts that doesn't look like C, so I hope you understand my
> request in this context. 

If I've misunderstood your request, please clarify.

Thanks.

Janis

> 
> Thanks,
> 
> John
> 
>>
>> Thanks.
>>
>> Janis

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Thread

getline timeout (revisited) Janis Papanagnou <janis_papanagnou@hotmail.com> - 2011-04-08 14:23 +0200
  Re: getline timeout (revisited) arnold@skeeve.com (Aharon Robbins) - 2011-04-10 18:49 +0000
  Re: getline timeout (revisited) j.eh@mchsi.com - 2011-04-19 09:09 -0500
    Re: getline timeout (revisited) Janis Papanagnou <janis_papanagnou@hotmail.com> - 2011-04-19 17:38 +0200
      Re: getline timeout (revisited) j.eh@mchsi.com - 2011-04-20 06:51 -0500
        Re: getline timeout (revisited) Janis Papanagnou <janis_papanagnou@hotmail.com> - 2011-04-20 14:20 +0200
          Re: getline timeout (revisited) j.eh@mchsi.com - 2011-04-20 08:21 -0500
            Re: getline timeout (revisited) j.eh@mchsi.com - 2011-04-21 05:46 -0500
            Re: getline timeout (revisited) arnold@skeeve.com (Aharon Robbins) - 2011-04-22 13:55 +0000
              Re: getline timeout (revisited) Grant <omg@grrr.id.au> - 2011-04-23 06:50 +1000

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