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Validating alphanumeric characters and entering data from an HTML form

I am new to Perl programming and have several compilation problems that I cannot solve. My program is getting data from this HTML form.

Question: Should my form use a message or get method?

<FORM action="./cgi-bin/Perl.pl" method="GET">
     <br>
     Full name: <br><input type="text" name="full_name" maxlength="20"><br>
     Username: <br><input type="text" name="user_name" maxlength="8"><br>
     Password: <br><input type="password" name="password" maxlength="15"><br>
     Confirm password: <br><input type="password" name="new_password" maxlength="15"><br>

I open a CSV file, write the user_name value to an array, and do a series of checks on the user login.

Problem # 1: I need to check that the fully qualified username, username, password and new_password are alphanumeric or spaces, but I keep getting a few errors that look like this:

Use of uninitialized value $full_name in string eq at Perl.pl line 33

I don't think I used the CGI correctly to get these values ​​from the form. I also believe that I am checking alphanumeric characters incorrectly. How can I solve this?

Problem # 2: I need to redirect a user to a specific web page if their passwords don't match and if the username has already been met. I've used a meta redirect, but it's not as successful. How can I show the correct error page?

This is my code:

#!/usr/bin/perl 
use CGI qw(:standard);
use strict;
use warnings;

print "Content-type: text/html\n\n";

#opening Members.csv for reading
my $file = '/home/2014/amosqu/public_html/cgi-bin/Members.csv';
open(my $csv, '<', $file)  || die "Could not open your file";

#getting these from HTML form
my $full_name = param('full_name');
my $user_name= param('user_name');
my $password = param('password');
my $new_password = param('new_password');

my @users = ();

#splitting each line of csv file
foreach (<$csv>) {
     chomp;
     my @fields = split (/\,/);
     push @users, $fields[1]; #put all usernames inside of array
}

close $csv;

#opening Members.csv for appending
open(my $fh, '>>', $file) || die "Could not open your file";

#SOURCE OF PROBLEM 1
#checking that all values are alphanumeric
if(($full_name && $user_name && $password && $new_password) eq /\A[[:alnum:]]+\z/) {
      #if passwords don't match, redirect to error page
      if($password ne $new_password){
         print qq(<html>\n);
         print qq(<head>\n);
         print qq(<title> Passwords don't match. </title> \n);
         print qq{<meta http-equiv="refresh"content="5;URL="http://www.cs.mcgill.ca/~amosqu/registration.html">\n};
         print qq(</head>\n);
         print qq(<body>\n);
         print qq(<b><center> Passwords don't match </b></center>\n\n);
         print qq(</body>\n);
         print qq(</html>\n);
     }
      #if they do match, check that user name isn't in Members.csv
      else { 
          if(grep (/$user_name/, @users)) {
             print qq(<html>\n);
             print qq(<head>\n);
             print qq(<title> Sorry username already taken. </title>\n);
             print qq{<meta http-equiv="refresh"content="5;URL="http://www.cs.mcgill.ca/~amosqu/registration.html">\n};
             print qq(</head>\n);
             print qq(<body>\n);
             print qq(<b><center> Username already taken. </b></center>\n\n);
             print qq(</body>\n);
             print qq(</html>\n);
        }
        #if it isn't already in Members.csv append values to the file
        else { 
             print $fh "$full_name, $user_name, $password \n";
       }
    }
}

close $fh;
+3


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1 answer


This should get you started. There are a number of issues with your code that don't stop it from working, but the current wisdom is not to use CGI

at all, so I'll roll with you.



  • Use GET

    if you don't have a compelling reason to usePOST

  • The problem is here

    if(($full_name && $user_name && $password && $new_password) eq /\A[[:alnum:]]+\z/) {

    You are using a Boolean operation &&

    , which concatenates the truth of three variables and checks if it matches as a string the content matches $_

    this regular expression.

    You have to test each of the variables separately and use the bind operator =~

    to test them against a regular expression. This is also a bad form of using POSIX character classes. I suggest you use grep

    like this

    my $mismatch = grep /[^A-Z0-9]/i, $full_name, $user_name, $password, $new_password;

    Now $mismatch

    true if any of the variables contains a non-alphanumeric character. (Strictly, it is set to the number of variables that have a non-alphanumeric character, which is zero (false) if none of them do.)

    Then you can say

    if (not $mismatch) { ... }

  • It looks like you just need else

    one that creates a separate page.

+2


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