there are several different kinds of regex, is this for a passwd script?

some pretty standard ones are [A-Z] && [a-z] && [0-9], that should at least get you through the must require cap letters, lowercase letters and a number. The rest will depend on what you are running, such as awk, sed, grep, etc....
Let me know if this helps and what you are running this on and I'll be glad to help ya out.

I am kind of learning as I go. you are able to test for length of a string using this method

so this will test for a variable with the lengths inbetween 6 and 11

this will check if the lenght is between 6 and 11

this will check if you have at least one lowecase letter

this will check if you have at least one uppercase letter

this will check if you have at least one number

this will check if you have a letter at the end, either upper or lowercase

I am not sure(yet) how to determine if all of the chartacters are iether numbers, or letters, no special character. Example $%&^.

I will let you know what I figure out :-)

you can use this to check to see if your script has any characters other then numbers or letters
this will return a 0 if any non letters or numbers are found.

It would be very easy to combine all of these tests into a single script. I learned quite abit myself while looking for this info :-)