Re: How to redirect stdout

Hi there,
Following my question about "stdout redirection in Gprolog", Gurvan Le 
Guernic gave a general
  answer ("script" command under Unix/Linux) that did the job.
I post it hereby.

This works not only for Gprolog but also for any command.
In order to gather (to mirror) outputs,  launch " script -c gprolog 
myfile" and "myfile" is a mirrir of the stdout :
(see "man script" also).

Here's an example (sorry for Windoz users !):
---------------------------------------------------------

alex@safran:> script -c gprolog toto
Le script a débuté, le fichier est toto
GNU Prolog 1.2.16
By Daniel Diaz
Copyright (C) 1999-2002 Daniel Diaz
| ?- write(1).
1

yes
| ?- listing.

yes
.......................

| ?- halt.

Script complélé, le fichier est toto
alex@safran:>

alex@safran:> cat toto
Le script a débuté sur mar 01 mar 2005 19:58:00 CET
GNU Prolog 1.2.16
By Daniel Diaz
Copyright (C) 1999-2002 Daniel Diaz
| ?- write(1).
1

yes
| ?- listing.

yes
.....................
| ?- halt.
Script complété sur mar 01 mar 2005 19:58:10 CET
---------------------------------

AS

Alexandre Saidi a écrit :
> Dear Lindsey,
> In my question, 'lising' was juste an (unfortunate) example !
> 
> I learned however how I'll do  for thisparticular  predicate.
> 
> I dont want to boder you so much (specially  Gurvan Le Guernic gave an 
> answer that's quite ok, for this task and so forth. Merci beaucoup à 
> Gurvan Le Guernic).
> 
> However, I tried  the following with no sucess.
> Don't worry. things seem much tighter !
> 
> I want to thak you for all your answers and post this one :
> Is there any way to have documents (other than "taking a deep look" at 
> the source of gprolog) to know these low-level predicats ?
> Answers would come from there, if any.
> 
> cheers.
> Merci
> --------------------------------
> alex@safran:~> gprolog
> GNU Prolog 1.2.16
> By Daniel Diaz
> Copyright (C) 1999-2002 Daniel Diaz
> | ?- [user].
> compiling user for byte code...
> entier(0).
> entier(succ(N)) :- entier(N).
> 
> user compiled, 3 lines read - 346 bytes written, 5319 ms
> 
> yes
> | ?- open(fichier,write,F), current_input(I), current_output(O), 
> '$set_top_level_streams'(I, F),entier(succ(succ(0))), 
> '$set_top_level_streams'(I, O), close(F).
> 
> F = '$stream'(2)
> I = '$stream'(0)
> O = '$stream'(1)
> 
> yes
> | ?- halt.
> 
> ZZZ : I tried with other examples that normaly give 'yes' or 'no' withe 
> variables or not.
> 
> ---------------------------------
> 
> Lindsey Spratt a écrit :
> 
>> I did some more investigating...
>>
>> The particular predicate with which you are testing the redirection of 
>> output, listing/0, sends its output to the "top level output", not 
>> stdout. So, redirecting stdout doesn't affect the output of listing/0.
>>
>> Here is an approach that does redirect the output of listing/0, using 
>> the internal '$set_top_level_streams'/2 predicate:
>>
>> ======
>> [Lindsey-Spratts-Computer:~/Documents] lindsey% gprolog
>> GNU Prolog 1.2.16
>> By Daniel Diaz
>> Copyright (C) 1999-2002 Daniel Diaz
>> | ?- [user].
>> compiling user for byte code...
>> toto:-true.
>> user compiled, 2 lines read - 205 bytes written, 8773 ms
>>
>> yes
>> | ?- open(fichier,write,F), current_input(I), current_output(O), 
>> '$set_top_level_streams'(I, F), listing, '$set_top_level_streams'(I, 
>> O), close(F).
>>
>>
>> F = '$stream'(2)
>> I = '$stream'(0)
>> O = '$stream'(1)
>>
>> yes
>> | ?- halt.
>> [Lindsey-Spratts-Computer:~/Documents] lindsey% cat fichier
>>
>> toto.
>> [Lindsey-Spratts-Computer:~/Documents] lindsey%
>> =====
>>
>> The redirection using set_output/1 should work when redirecting the 
>> output from the 'write/1' predicate.
>>
>> Cheers,
>> Lindsey Spratt
>>
>> On Mar 1, 2005, at 11:30 AM, Alexandre Saidi wrote:
>>
>>> Thanks Lindsey,
>>> I've been trying any thing I could to make it work.
>>> Ther's no way !
>>> As I said, I saw a mail in the FAQ saying that stdout is not affected 
>>> by set_output.
>>> I'm using the version 1.2.16.
>>> Perhaps ther'is is a trick withe the interactive mode ?
>>>
>>> Thanks any way.
>>> ---------------------------------------------
>>> Here's what I do under prolog (for a test) :
>>> alex@safran:~> gprolog
>>> GNU Prolog 1.2.16
>>> By Daniel Diaz
>>> Copyright (C) 1999-2002 Daniel Diaz
>>> | ?- [user].
>>> compiling user for byte code...
>>> toto :- true.
>>>
>>> user compiled, 2 lines read - 207 bytes written, 4104 ms
>>>
>>> yes
>>> | ?- open(fichier,write,F), current_output(Old), set_output(F), 
>>> listing, flush_output(F), flush_output, close(F).
>>>
>>> toto.
>>>
>>> F = '$stream'(2)
>>> Old = '$stream'(1)
>>>
>>> (1 ms) yes
>>> | ?- halt.
>>> alex@safran:~>
>>>
>>> The file 'fichier' is empty.
>>> I've done many other tests with no success.
>>> ---------------------------------------------------------
>>>
>>> Lindsey Spratt a écrit :
>>>
>>>> Perhaps flush_output(F) before the close(F), or simply 
>>>> 'flush_output', would help.
>>>> Lindsey
>>>> On Mar 1, 2005, at 3:04 AM, Alexandre Saidi wrote:
>>>>
>>>>> Thanks for your help.
>>>>>
>>>>> I'd already tried :
>>>>>
>>>>> | ?-open('/home/alex/fichier',write,F), current_output(Old), 
>>>>> set_output(F), a_call, close(F), set_output(Old).
>>>>>
>>>>> But the file 'fichier' is of size 0 !
>>>>>
>>>>> So what's wrong with my code?
>>>>> should I flush something ?
>>>>>
>>>>> regards.
>>>>>
>>>>> AS
>>>
>>>
>>>
>>> -- 
>>> Aleksander S. Saidi
>>> Ecole Centrale de Lyon
>>> Département Mathématiques-Informatique
>>> Mél : [email protected]
>>> Tél : 04.72.18.65.30, Fax : 04.78.33.16.15
>>>
>>
>>
> 

-- 
Aleksander S. Saidi
Ecole Centrale de Lyon
Département Mathématiques-Informatique
Mél : [email protected]
Tél : 04.72.18.65.30, Fax : 04.78.33.16.15