CODEWITHSUNDEEP
regexgo
wordSmith
wordSmith

Reputation: 3183

Regex for starting with alphanumeric and hyphen, underscore later in string

I'm trying to write a regexp in golang that matches strings that start as alphanumeric and can have an underscore or hyphen after, but not starting with a hyphen or underscore.

Here is what I could come up with, but this matches alphanumeric and hyphen underscore anywhere

[A-Za-z0-9_-]

So something like sea-food would match or seafood or sea_food, but not -seafood nor _seafood.

Upvotes: 1

Views: 7326

Answers (3)

Avinash Raj
Avinash Raj

Reputation: 174874

Keep it simple. You could use a negative lookahead at the start.

^(?![_-])[\w-]+$

DEMO

Upvotes: 2

Prestaul
Prestaul

Reputation: 85224

You need to use a ^ to indicate the start of the string and $ for the end, and then use two character classes:

^[A-Za-z0-9][A-Za-z0-9_-]*$

To disallow hyphens and underscores at the end of the string as well try:

^[A-Za-z0-9]([A-Za-z0-9_-]*[A-Za-z0-9])?$

Upvotes: 5

dhalik
dhalik

Reputation: 465

You need to split up your expression, and match the first character separately, and do the following:

[A-Za-Z][A-Za-z0-9_-]*

Upvotes: 0

Related Questions