#!perl
# Figure 19.4: fig19_04.pl
# Preventing improper input.

use warnings;
use strict;
use CGI qw( :standard );

print( header(), start_html( "Prevent improper input" ) );

my $cgi = new CGI();

unless ( $cgi->param() ) {
   print( "Type some text, then press Enter",
          " and I will display it for you." );
   my $form = new CGI();
   print( $form->startform(),
          $form->textfield( 'words', '', 20 ),
          $form->endform() );
}
else {
   my $words = $cgi->param( 'words' );
   print( "You entered: $words.", br() );

   if ( $words =~ /^\w*$/ ) {
      print( "Attempting to execute: $words.", br() );
      my @matches = `$words`;  
      
      if ( @matches ) {
         print( br(), join( br(), @matches ) );
      }
      else {
         print( "'$words' was not a shell command.", br() ); 
      }
   }
   else {
      print( "Invalid input. Re-enter without any symbols." );
   }
}

print( end_html() );

###########################################################################
#  (C) Copyright 2001 by Deitel & Associates, Inc. and Prentice Hall.     #
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