Validating UK Post Codes using regular expressions

Question

I want to validate a field with a UK Post Code. What regular expression could be used to validate this field?. (([A-Z]{1,2}[0-9][0-9A-Z]{0,1})\ ([0-9][A-Z]{2}))|(GIR\ 0AA)$ does appear valid because it has the exception GIR 0AA.

So, please help me to write an expression without any exception

Answer 1

If you do mean post code, wikipedia has a section on validation. One regex that it recommends is:

((A[BL]|B[ABDHLNRST]?|C[ABFHMORTVW]|D[ADEGHLNTY]|E[HNX]?|F[KY]|G[LUY]?|H[ADGPRSUX]|I[GMPV]|JE|K[ATWY]|L[ADELNSU]?|M[EKL]?|N[EGNPRW]?|O[LX]|P[AEHLOR]|R[GHM]|S[AEGKLMNOPRSTY]?|T[ADFNQRSW]|UB|W[ADFNRSV]|YO|ZE)[1-9]?[0-9]|([E|N|NW|SE|SW|W]1|EC[1-4]|WC[12])[A-HJKMNPR-Y]|[SW|W]([1-9][0-9]|[2-9])|EC[1-9][0-9]) [0-9][ABD-HJLNP-UW-Z]{2}

The advantage of this one is that it catches some invalid areas and districts.