Underscore or hiphen should come once but not at boundaries

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July 16th, 2009, 07:58 AM

gurjeet

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Join Date: Dec 2007

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Underscore or hiphen should come once but not at boundaries

Hi

I am in a fix

i need to write a regular expression for this situation...

1) a-z and 0-9 allowed with _ or -
2) _ or - should not come more than one; and should not be at the boundaries and both cannot come together
3) range : 3 to 16

Examples::
1) te-st = true
2) test = true
2) te-_st = false
3) -test or test_ = false

This is what i came up with so far

Code:

^([a-z0-9]+(-|_)?[a-z0-9]+){3,16}$

Thank you for any help

July 16th, 2009, 03:03 PM

prometheuzz

User 165270

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This will do the trick:

Code:

^(?!.*[_-]{2})[a-z0-9][a-z0-9_-]{1,14}[a-z0-9]$

July 16th, 2009, 11:34 PM

gurjeet

Registered User

Join Date: Dec 2007

Posts: 29

Time spent in forums: 9 h 26 m 42 sec
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Quote:

Originally Posted by prometheuzz

This will do the trick:

Code:

^(?!.*[_-]{2})[a-z0-9][a-z0-9_-]{1,14}[a-z0-9]$

Thank you
It solved the problem.

Just wondering how can we modify this expression to eliminate the double occurence of symbols

i.e. currently it is validating t-e_s and t-e-s but i want to allow people to use any of the symbol (_ or -) only once.
expression should not validate t-e_s and t-e-s..