scripting - ruby script to enter prompt command from a system command -

I am trying to write some DBS mysqldump as a simple script I'm stuck at the password prompt though.

I have only one config file, which contains all DB credits, then the script can be used to connect those people to DB.

The problem is a command like:

  system ('mysqldump -u username -p')   
 then prompts for  
  Enter password:   
 Even when I do something like this:  
  System ( 'Mysqldump -u usernames -p some_password')   
 I still get a prompt for the password ...  
 In Ruby I can not do lots of scripting I am in harm's way why my script is automatically reporting this information Can Rg so does not require the user to run the script.   
 
 
 You  -p   
  system ('Mysqldump -uusername -psome_password')   
 or delete the location without a password  
  system ('mysqldump -username')   
 or  
  system ('mysqldump -username --password =')