From: Justin White <just6979@...>
Date: 2003-03-18T14:22:47+09:00
Subject: Parsing a CGI query (Re: Your favorite Ruby web library?)


On Sunday, March 16, 2003, at 07:08 , Eric Hodel wrote:

> Provided you can run a CGI, Borges should work.  If you're not using
> mod_ruby, you'll have to figure out how to grab the GET and POST args
> yourself, because I've not puzzled that out yet.

i have. i'll put it down here, for you and to make sure i actually know 
what i'm doing (check my sanity fellow Rubyists :P )

CGI data is stored in environment variables passed to the CGI 
executable. use Ruby's global ENV Hash to retrieve them. 
ENV['REQUEST_METHOD'] is GET or POST. for GET requests, 
ENV['QUERY_STRING'] is the string after the question mark in the URL.
for example: cgi.rb?key=val;foo=bar
   QUERY_STRING = 'key=val;foo=bar'

split QUERY_STRING on ';' or '&'. i use semicolons because it doesn't 
affect URL encoding routines like an ampersand might, but my scripts 
check for & just in case. they're both valid as far as i know. then 
split each element on '=' to get your keys and values.

a very simple GET query parser could look like this:
   ## CGI GET query parser
   params = {}
   ENV['QUERY_STRING'].split(/[;&]/).each { |pair|
     key, val = pair.split(/=/)
     params[key] = val
   }
   ## end

note that this simple parser will overwrite repeated keys, which is not 
standards compliant. Ruby's cgi.rb always puts them in an Array to be 
safe (params[key].push val). ask me or see Perl5's CGI.pl for another 
way to deal with it. (my way is Perl5's in Ruby :P )

extra: PATH_INFO is also filled in, if the script name is followed by 
a / and some text in the request URL. PATH_TRANSLATED is PATH_INFO 
appended to the httpd's DocumentRoot. following the path with an 
optional question mark can create a QUERY_STRING as well as the 
PATH_INFO.
for example: cgi.rb/foo/bar?key=val
   PATH_INFO = '/foo/bar'
   QUERY_STRING = 'key=val'

i haven't done any POST work yet, but i believe it's mostly the same, 
with some checking of CONTENT_LENGTH and such to ensure you have the 
data you want.

happy hacking!


-Justin White

just6979@yahoo.com
http://tin.2y.net/
AIM: just6979