RegEx that matches positive numbers

I need to write a regex to allow only positive number ( integers or decimals). I have found this:

/^(?!(?:0|0\.0|0\.00)$)[+]?\d+(\.\d|\.\d[0-9])?$/  

but it just accepts up to 2 decimal places. What changes do I have to make, so that it can accept any number of decimal places?

Also where can I find a good tutorial for learning regex.

Thanks beforehand

This would be my way: ^[+]?\d+([.]\d+)?$
EDIT: If you want to allow something like .23, you could use ^[+]?([.]\d+|\d+([.]\d+)?)$
EDIT: tchrist insists on this one: allowing 4., you could use ^[+]?([.]\d+|\d+[.]?\d*)$

Explanation:

• with or without positive sign
• one or more digits
• with or without:
  • decimal point
  • one or more digits

Note: This will not accept a negative number, which is what you ultimately want.