Question

I have learned several ways to query forms, they all work. But, for heavens sake, I don't know why!!!

For example, this:

%SEARCH{ "[S]chool Type.*value=.[I]nstrumentality"  

What do the brackets around "S" and "I" mean? Why does value have a "*" in front of it? Why is there a "." before the search value, "Instrumentality?"

And, this:

META\:FIELD.*?SchoolType.*?Instrumentality"

What does *? mean? I know if I remove them, it no longer works.

I guess I should be happy that it works, but it bugs me not to understand and I have looked all over the place. Where is the documentation on this?

Environment

-- JohnGee - 10 Jun 2008

Answer

If you answer a question - or someone answered one of your questions - please remember to edit the page and set the status to answered. The status selector is below the edit box.

This is a RegularExpression search question. Regular expressions are more powerful than literal search, but they are quite geeky and need some time to learn. TWiki 4.2 offers a QuerySearch that makes advanced somewhat searches easier.

To your questions:

• [aiueo] finds exactly one vowel, [S] finds exactly one character S. So why a single char in [...]? That is to exclude the search page from showing up in a search result. The same can be achieved with an excludetopic parameter. These two searches are identical
  %SEARCH{ "[S]chool Type.*value.[I]nstrumentality" type="regex" ...=
  %SEARCH{ "School Type.*value.Instrumentality" type="regex" excludetopic="%TOPIC%" ...=
  
• .*? is a cautious scan forward ("non greedy search"), skipping over any character until the first pattern following it is found. The greedy .* pattern scans forward and finds the last pattern.

Learn more at RegularExpression, Wikipedia:Regular_expression, http://www.perl.com/doc/manual/html/pod/perlre.html

-- PeterThoeny - 10 Jun 2008