http://www.perlmonks.org?node_id=1011763


in reply to Re: Unwanted parameter when executing CGI scripts
in thread [SOLVED] Unwanted parameter when executing CGI scripts

After thinking again about your code, I have one question and one additional remark. Please note that C and assembler is my main business, so I am usually using the sort of Perl syntax which is similar to C, and I might have misunderstood what you are doing in your code. Anyways:

delete $cgi->{param}{keywords} if length && !/[&=]/;

Do I get this right: The "keywords" parameter is deleted if the length of the query string is >0 and the query string does not contain = or &? The code would then fail when the script would be called without any query string (which was the situation where I was surprised by the problem the first time). If I am right, we should write

delete $cgi->{param}{keywords} if (!defined || !length || !/[&=]/;

instead. Correct?

One more problem / remark: Suppose the script is called via

/cgi-bin/script.pl?Test

CGI.pm then would generate a parameter "keywords=Test", and we would remove that parameter accordingly. But that would be only the half of the way: I think that "Test" in that case should be a KEY in the parameter list which has an empty (or undefined) value. How exactly should we handle this? What is the difference between the following calls (from the viewpoint of the CGI specification)?

/cgi-bin/script.pl
/cgi-bin/script.pl?
/cgi-bin/script.pl?Test
/cgi-bin/script.pl?Test=

[download]

Of course, I'd test myself before boring others, but I am not sure if it would be a good idea to find out by using CGI.pm or Plack, because I now have learned that (at least) CGI.pm does unexpected things, so I could not use that for testing. Not sure about Plack, though.

Regards,

Nocturnus

Replies are listed 'Best First'.
Re^3: Unwanted parameter when executing CGI scripts
by tobyink (Canon) on Jan 05, 2013 at 14:00 UTC

    You needn't test for whether $ENV{QUERY_STRING} is defined or not, because undefined things automatically have zero length.

    "CGI.pm then would generate a parameter "keywords=Test", and we would remove that parameter accordingly. But that would be only the half of the way: I think that "Test" in that case should be a KEY in the parameter list which has an empty (or undefined) value."

    Then you could try something like:

    for ($ENV{QUERY_STRING}) {
   $cgi->{param}{delete $cgi->{param}{keywords}} = ""
      if length && !/[&=]/;
}

    [download]
    perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'
[reply]
[d/l]
[select]

      Thank you very much for your answer, but I just haven't got it yet. Please forgive me if I'm too stupid, but I think you are testing if the query string's length is >0, and your code only gets executed if this condition is true.

      But when calling the script without any parameters, the length of the query string is 0, and that evaluates to false, so the whole line doesn't get executed.

      Please correct me if I am wrong.

      Regards,

      Nocturnus

[reply]

        Indeed, the whole line doesn't get executed. But the line doesn't need to be executed because there's no query string. Thus there will be no keywords; nothing to clean up; no work needs to be done.

        perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'
[reply]

In Section Seekers of Perl Wisdom