How to Create a Log in Script in Perl Without the Use of Databases

Perl is one of the most widely used languages the world. With a huge collection of modules (see CPAN) and easy-to-learn syntax, there's no wonder why. One of Perl's modules is able to access popular databases (Oracle, MySQL) is very useful, but can be confusing at some time. This article will show you how to create a log in script in Perl without databases involved.

1. Create the subs that will be on the code.
   • sub change {
   • my($a) = @_;
   • chdir "$a" or die "ERROR: $!";
   • }
     • sub is a subroutine/function declaration. This code can function by typing either change("test") or &change("test").
     • my is the word of a special variable designed for only the block of code (a block is {}). Similar in math class, a variable is a placeholder that holds bytes.
     • chdir is another word for "change directory". A substitute is system "cd $a", in this case.
     • or are logical operators with true and false as the "answers".
     • die is a command that prints the message to STDERR (another name for "Standard Error"). $! and $@ represent why the command failed, and can be added to die, as well as others.
2. Remember, all commands end with a semicolon.
3. Create a message that will say to either register or log in, then add code to accept input.
   • print "Do you want to register or log-in? "; chomp($a=<STDIN>);
   • print is a word meaning to print data.
   • chomp is a function to chop of the newline that the nasty <STDIN> leaves after input. You could also use the chop command.
4. Add an "if" command.
   • if($a =~ /register/i) {
   • # Stuff goes here...
   • }
   • if is a boolean condition block with true or false.
   • =~ means to compare to a regular expression operator. If you use UNIX/LINUX or something similar, the grep command should be similar.
   • /register/i is the text that the regular expression should compare to. The / means to start, the word register is the code the operator will compare to, and the second / means to end. The letter i means to use case-insensitivity, as case-sensitivity is commonly used.
   • # is to signify a comment. The rest of the line is commented, the text will be ignored by the compiler.
   • { to } represents a block. These will be executed when called.
5. Create some more input.
   • print "What is your name: "; chomp($name=<STDIN>);
   • print "What is your password: "; chomp($password=<STDIN>);
6. Before proceeding on, make sure you have two folders named "name" and "password".
7. Write the name and password. Remember to add this between the two curly braces!
   • #* change "name";
   • open NAME, ">$name.nme";
   • print NAME "$name";
   • close NAME;
   • change "..";
   • change "password";
   • open PASSWORD ">$name.pswrd";
   • print PASSWORD "$password";
   • close PASSWORD;
   • change "..";
   • print "Complete.\n";
     • change is the function we wrote when we first wrote the program. The function would change directory to the name we specified.
     • open NAME, ">$name.nme" or open PASSWORD, ">$name.pswrd" will "open the file" on the second parameter (>$name.nme or something close), and give a "name" to it, known as filehandle. The name is the first parameter (like NAME or PASSWORD). The > sign in the files name represents "types". < and nothing are reading, > is writing (overwrites anything) and >> is appending (writes additional stuff).
     • print NAME or print PASSWORD is a command. In this case, we use the print function to print data to a filehandle, which then will be processed and (with the > and >>) added.
     • change ".." is using the change we added to go back a directory. The command for going back is "..".
     • \n represents a newline.
8. Add the log-in block.
   • else {
   • print "Name: "; chomp($a=<STDIN>);
   • print "Password: "; chomp($b=<STDIN>);
   • change "name";
   • open NAME "$a.nme";
   • $c=<NAME>;
   • close NAME;
   • change "..";
   • change "password";
   • open PASSWORD "$a.pswrd";
   • $d=<PASSWORD>;
   • close PASSWORD;
   • change "..";
   • if($a =~ /$c/ and $b =~ /$d/) {
   • print "Log-in successful!\n";
   • sleep(2);
   • print "Hello, $a!\n";
   • }
     • else is if the if test failed. The compiler will run the block.
     • $c=<NAME> or $d=<PASSWORD> means that the variable's data will be assigned to the filehandle specified.
     • sleep(2) means that the compiler should wait for the number specified. 2 means to wait for two "blinks" on the prompt.
     
     
     

     The code altogether

     
     
   • sub change {
   • my($a) = @_;
   • chdir "$a" or die "ERROR: $!";
   • }
   • print "Do you want to register or log-in? "; chomp($a=<STDIN>);
   • if($a =~ /register/i) {
   • print "What is your name: "; chomp($name=<STDIN>);
   • print "What is your password: "; chomp($password=<STDIN>);
   • change "name";
   • open NAME, ">$name.nme";
   • print NAME "$name";
   • close NAME;
   • change "..";
   • change "password";
   • open PASSWORD ">$name.pswrd";
   • print PASSWORD "$password";
   • close PASSWORD;
   • change "..";
   • print "Complete.\n";
   • }
   • else {
   • print "Name: "; chomp($a=<STDIN>);
   • print "Password: "; chomp($b=<STDIN>);
   • change "name";
   • open NAME "$a.nme";
   • $c=<NAME>;
   • close NAME;
   • change "..";
   • change "password";
   • open PASSWORD "$a.pswrd";
   • $d=<PASSWORD>;
   • PASSWORD;
   • "..";
   • if($a =~ /$c/ and $b =~ /$d/) {
   • print "Log-in successful!\n";
   • 2);
   • "Hello, $a!\n";
   • • Well done! You completed a program!
     • This code can be easily hacked. Try writing the code on hex if your adventurous. 
     
     Source : www.wikihow.com
     

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