How to execute procedure in the background ??

[JaMEs CoRN 0.0.7.]

Hi all..
let's say I have a self-defined Tcl procedure GETPOSN :

GETPOSN {
while {} {
... assign values to global variables
}
}

values are returned from a server program in the while loop and these values are
assigned to global variables to be used in the execution of the program .. is there a
way I can make the procedure GETPOSN run in the background ??

ps : I'm new to Tcl .. TIA for any help ...
--
.__J.a.M.E.s...c.0.R.n..000..000..111.__.
: email: james...@pobox.org.sg :
:_web: http://www.iscs.nus.sg/~tanpuayh_:

[Frederic Bonnet]

JaMEs CoRN 0.0.7. wrote:
>
> Hi all..
> let's say I have a self-defined Tcl procedure GETPOSN :
>
> GETPOSN {
> while {} {
> ... assign values to global variables
> }
> }
>
> values are returned from a server program in the while loop and these values are
> assigned to global variables to be used in the execution of the program .. is there a
> way I can make the procedure GETPOSN run in the background ??

No, at least in standard Tcl.
I think the BLT extensions provide a way to evaluate scripts in the background.

I guess you use sockets to communicate with the server. In this case you can use
fileevents on sockets, in order to call a handler in the background each time the
server sends a value.

Regards, Fred

--
Frederic BONNET Eleve-Ingenieur de l'Ecole des Mines de Nantes
fbo...@irisa.fr Stagiaire IRISA - Projet Solidor

"Il ne faut jamais remettre au lendemain ce qu'on peut faire le surlendemain"
Oscar WILDE

[JaMEs CoRN 0.0.7.]

JaMEs CoRN 0.0.7. (tanp...@iscs.nus.sg) wrote:
: values are returned from a server program in the while loop and these values are

: assigned to global variables to be used in the execution of the program .. is there a
: way I can make the procedure GETPOSN run in the background ??

something to add on ... I would like GETPOSN to run in the background, or better
still, to run as a separate thread that is created at the start of the program.. is there
a way to do this ??.. TIA.

[Yves Mathys]

>>>>> "JaMEs" == JaMEs CoRN 0 0 7 <tanp...@iscs.nus.sg> writes:
In article <4s2dou$c...@nuscc.nus.sg> tanp...@iscs.nus.sg (JaMEs CoRN 0.0.7.) writes:

JaMEs> Hi all..
JaMEs> let's say I have a self-defined Tcl procedure GETPOSN :

JaMEs> GETPOSN {
JaMEs> while {} {
JaMEs> ... assign values to global variables
JaMEs> }
JaMEs> }

JaMEs> values are returned from a server program in the while loop and these values are
JaMEs> assigned to global variables to be used in the execution of the program .. is there a
JaMEs> way I can make the procedure GETPOSN run in the background ??

Look at 'after' command to push procedure on the event queue.

-Yves
--

Yves Mathys Europe Design Technology
mat...@ssdtgva.sps.mot.com High Level Modeling
Motorola Inc
Phone: (41-22) 799 12 28 207, route de Ferney/CP 15
FAX: (41-22) 799 13 04 1218 Grand-Saconnex,Switzerland

[Donal K. Fellows]

In article <4s4aqe$a...@nuscc.nus.sg>,

JaMEs CoRN 0.0.7. <tanp...@iscs.nus.sg> wrote:
> JaMEs CoRN 0.0.7. (tanp...@iscs.nus.sg) wrote:

>> values are returned from a server program in the while loop and

>> these values are assigned to global variables to be used in the
>> execution of the program .. is there a way I can make the procedure

>> GETPOSN run in the background ??
>

> Something to add on ... I would like GETPOSN to run in the

> background, or better still, to run as a separate thread that is
> created at the start of the program.. is there a way to do this?

You are not thinking in event-based terms.

If the values from the server are arriving on channel ServerChan (a
socket or pipe), then you want to arrange for a procedure to be called
every time a new value is available from ServerChan. This means that
you need to do a bit of coding with fileevent

proc getOnePosn {} {
global ServerChan
if {[gets $ServerChan line] < 0} {
close $ServerChan
# The server has gone away!?
} else {
# ... Do Something with the line just read ...
}
}
fileevent $ServerChan readable getOnePosn

Now you need to make sure that you enter the Tcl event loop (Tk event
loop for 7.4/4.0) using tkwait or vwait.

Donal.
--
Donal K. Fellows, (at work) | Donal K. Fellows, (at home)
Dept. of Computer Science, | 6, Randall Place, Heaton,
University of Manchester | Bradford, BD9 4AE
U.K. Tel: ++44-161-275-6137 | U.K. Tel: ++44-1274-401017
fell...@cs.man.ac.uk (preferred) | do...@ugglan.demon.co.uk (if you must)
--------------------------------------------------------------------------
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[Nenad Cimerman]

In article <31E53621...@irisa.fr>, Frederic Bonnet <fbo...@irisa.fr> writes:
|> JaMEs CoRN 0.0.7. wrote:
|> >
|> > Hi all..

|> > let's say I have a self-defined Tcl procedure GETPOSN :
|> >

|> > GETPOSN {
|> > while {} {

|> > ... assign values to global variables
|> > }
|> > }
|> >

|> > values are returned from a server program in the while loop and these values are
|> > assigned to global variables to be used in the execution of the program .. is there a
|> > way I can make the procedure GETPOSN run in the background ??
|>

Maybe it's even not such a very good idea to modify global variables from
the background ... How about using the 'send'-command from a seperate script,
which can be started like: exec ListenToServer.tcl
You could implement callback functions for received data and call them
remotely via the send-command (see man-page).

Another way to perform background tasks is to use the 'after'-command:

proc SayHi {} {
puts stdout 'Hi there'

after 1000 SayHi
}

SayHi

Bye,
--
Nenad Cimerman

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