Searching for UUIDs in text with regex

I'm searching for UUIDs in blocks of text using a regex. Currently I'm relying on the assumption that all UUIDs will follow a patttern of 8-4-4-4-12 hexadecimal digits.

Can anyone think of a use case where this assumption would be invalid and would cause me to miss some UUIDs?

The regex for uuid is:

\b[0-9a-f]{8}\b-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-\b[0-9a-f]{12}\b

@ivelin: UUID can have capitals. So you'll either need to toLowerCase() the string or use:

[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}

Would have just commented this but not enough rep :)

Version 4 UUIDs have the form xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where x is any hexadecimal digit and y is one of 8, 9, A, or B. e.g. f47ac10b-58cc-4372-a567-0e02b2c3d479.

source: http://en.wikipedia.org/wiki/Uuid#Definition

Therefore, this is technically more correct:

/[a-f0-9]{8}-[a-f0-9]{4}-4[a-f0-9]{3}-[89aAbB][a-f0-9]{3}-[a-f0-9]{12}/

If you want to check or validate a specific UUID version, here are the corresponding regexes.

Note that the only difference is the version number, which is explained in 4.1.3. Version chapter of UUID 4122 RFC.

The version number is the first character of the third group : [VERSION_NUMBER][0-9A-F]{3} :

• UUID v1 :

  /^[0-9A-F]{8}-[0-9A-F]{4}-[1][0-9A-F]{3}-[89AB][0-9A-F]{3}-[0-9A-F]{12}$/i
  

• UUID v2 :

  /^[0-9A-F]{8}-[0-9A-F]{4}-[2][0-9A-F]{3}-[89AB][0-9A-F]{3}-[0-9A-F]{12}$/i
  

• UUID v3 :

  /^[0-9A-F]{8}-[0-9A-F]{4}-[3][0-9A-F]{3}-[89AB][0-9A-F]{3}-[0-9A-F]{12}$/i
  

• UUID v4 :

  /^[0-9A-F]{8}-[0-9A-F]{4}-[4][0-9A-F]{3}-[89AB][0-9A-F]{3}-[0-9A-F]{12}$/i
  

• UUID v5 :

  /^[0-9A-F]{8}-[0-9A-F]{4}-[5][0-9A-F]{3}-[89AB][0-9A-F]{3}-[0-9A-F]{12}$/i
  

I agree that by definition your regex does not miss any UUID. However it may be useful to note that if you are searching especially for Microsoft's Globally Unique Identifiers (GUIDs), there are five equivalent string representations for a GUID:

"ca761232ed4211cebacd00aa0057b223" 

"CA761232-ED42-11CE-BACD-00AA0057B223" 

"{CA761232-ED42-11CE-BACD-00AA0057B223}" 

"(CA761232-ED42-11CE-BACD-00AA0057B223)" 

"{0xCA761232, 0xED42, 0x11CE, {0xBA, 0xCD, 0x00, 0xAA, 0x00, 0x57, 0xB2, 0x23}}"