Database in ruby? HELP

#Simplest sign up & login form ever!

#Sign up process
print "Username: "
user = gets.chomp

print "Password: "
pass = gets.chomp

=begin
Now I want the given information to be saved in a file.
And later the program should be able to pull back the saved data.
So the user can sign in.
=end

#Login process

print "Username: "
user = gets.chomp

print "Password: "
pass = gets.chomp

=begin
Now the shell should look for the given username and password on the database and check if it's correct
And if it is, sign in else puts try again or something
=end