Re: How to simple exit in CGI?

> On 31 Mar 2017, at 00:55, Jean Louis <[email protected]> wrote:
> 
> On Thu, Mar 30, 2017 at 10:10:48PM +0200, Pascal Bourguignon wrote:
>> Neither using LISTEN or directly READ-SEQUENCE are good solutions.
>> Either one will work only by chance.
> 
> I guess that is deeper foundation of how it works. On my side it works
> now well, so it will work in practice.
> 

It will work until the system is loaded and the web server is interrupted between fork/execing the CGI, and writing the parameter.  


>> LISTEN in particular will fail, if for whatever reason, the web
>> server didn’t start writing the PUT data or POST parameters to the
>> CGI pipe, when the CGI calls LISTEN.  I guess the same is true with
>> READ-SEQUENCE: it won’t read an end-of-file if the web server
>> doesn’t close that pipe.
> 
> OK, maybe, I don't know, I cannot say. I just test it on 2-3
> webservers, those I use also remotely, if it works locally, it works
> remotely, then I leave it working for years.

Good luck!  Be sure to put your name on any system you program like that, so I don’t use them and don’t risk a painful death.

> 
>> And let me you ask the question: what reason does the web server
>> have to close that pipe if it didn’t have to write anything to it,
>> because it was a GET request?
>> 
>> The correct solution, as always, is to read the documentation,
>> specifically, the RFC 3875 <https://tools.ietf.org/html/rfc3875>
> 
>> Or you may browse the Wikipedia summary, and find out that the CGI
>> specifies that the environment variable REQUEST_METHOD will indicate
>> whether it’s a GET, a PUT, a POST or whatever else.  You must test
>> this before trying to read stdin!
> 
>> 
>> 
>> (defun main (&optional (arguments *args*))
>>  (let ((method (getenv "REQUEST_METHOD")))
>>    (cond ((or (string= method "PUT")
>>               (string= method "POST"))
> 
> Thank you.
> 
> I have just shown the sample, in reality I am testing for QUERY_STRING
> to get the GET parameters, if none, I test for *standard-input*, and
> later for certain parameters, if they are missing, it goes to error
> handling.

QUERY_STRING is present when REQUEST_METHOD=POST !
And there is an intersection of values for QUERY_STRING for both GET and POST.


-- 
__Pascal J. Bourguignon__



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