Recipe 19.10 Creating Sticky Widgets

19.10.1 Problem

You want form fields to default to the last values submitted. For instance, you want a search form like Google (http://www.google.com/) where the keywords you searched for appear in the search dialog above the results.

19.10.2 Solution

Use CGI.pm's HTML shortcuts to create your form, which automatically provides previous values as defaults:

print textfield("SEARCH");          # previous SEARCH value is the default

19.10.3 Discussion

Example 19-8 is a simple script for producing the list of users currently logged in.

Example 19-8. who.cgi

  #!/usr/bin/perl -wT
  # who.cgi - run who(1) on a user and format the results nicely
  
  $ENV{IFS}='';
  $ENV{PATH}='/bin:/usr/bin';
  
  use CGI qw(:standard);
  
  # print search form
  print header( ), start_html("Query Users"), h1("Search");
  print start_form( ), p("Which user?", textfield("WHO")); submit( ), end_form( );
  
  # print results of the query if we have someone to look for
  $name = param("WHO");
  if ($name) {
      print h1("Results");
      $html = '';
      
      # call who and build up text of response
      foreach (`who`) {
          next unless /^$name\s/o;            # only lines matching $name
          s/&/&amp;/g;                        # escape HTML
          s/</&lt;/g;
          s/>/&gt;/g;
          $html .= $_;
      }
      # nice message if we didn't find anyone by that name
      $html = $html || "$name is not logged in";
      
      print pre($html);
  }
  
  print end_html( );

The call to textfield generates HTML for a text entry field whose parameter name is WHO. After printing the form, we check whether we were called with a value for the WHO parameter. If so, we try to find lines in the output from who for that user.