validating last two characters to follow a pattern

Question

I have a string abcdefgh,

i want to check if the last two characters are alpha numeric/alphabets but not numeric

i.e. it can end in a1, 1a, aa but not 11

are there any regex gurus who can chipin

The regex should return the below results for the strings

abcd - True abc1d - True abcd1 - True abc12 - false

This is confusing: `11` *is* a string of alphanumeric characters. — Sven Hohenstein, Jan 21 '14 at 11:43
well that is my weird requirement though NN is alphanumeric in my case i should not allow it — Mohammed Rafeeq, Jan 21 '14 at 11:54
Questions asking for code must demonstrate a minimal effort in solving the actual problem, including the attempted code and the encountered issues — HamZa, Jan 21 '14 at 21:08

acdcjunior · Answer 1 · 2014-01-21T11:51:02.630

2

This should do it:

^.*(\d[a-zA-Z]|[a-zA-Z](\d|[a-zA-Z]))$

Online regex tool demo here.

Meaning:

^                       the beginning of the string
.*                      any character except \n (0 or more times)
(                        
 \d[a-zA-Z]             a digit (0-9) followed by any character of a to z, A to Z
 |                      OR
 [a-zA-Z]               any character of a to z, A to Z followed by
 (\d|[a-zA-Z])          a digit or any character of a to z, A to Z
)                         
$                       end of the string

Notice this matches the whole string, not only the two last chars, having those at the matched group one.

edited Jan 21 '14 at 11:51

answered Jan 21 '14 at 11:39

acdcjunior

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No, that doesn't match `aa`. – Peter Westlake Jan 21 '14 at 11:44
@PeterWestlake you're right. Fixed. – acdcjunior Jan 21 '14 at 11:45
Note - `(\d|[a-zA-Z])` = `[\da-zA-Z]`. – Bernhard Barker Jan 21 '14 at 11:52
it passes for a1, 1a but fails for aa – Mohammed Rafeeq Jan 21 '14 at 11:53
@MohammedRafeeq yeah, it did, but I edited. See the updated answer. – acdcjunior Jan 21 '14 at 11:56
yes this works finally – Mohammed Rafeeq Jan 21 '14 at 12:00

score 1 · Answer 2 · answered Jan 21 '14 at 11:43

So, a letter and a digit, or a digit and a letter, or two letters?

([a-zA-Z]\d|\d[a-zA-Z]|[a-zA-Z][a-zA-Z])$

Depending on the regex system you're using, you can also use character classes such as :alpha:, but this one will work for all of them. Some regex syntaxes need a backslash in front of the parentheses and/or pipe symbol.

score 0 · Answer 3 · answered Jan 21 '14 at 11:41

0

You can use

^.*[A-Za-z].|.[A-Za-z]$

Online test

answered Jan 21 '14 at 11:41

Sven Hohenstein

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No, that matches things that aren't digits, like `a!`. – Peter Westlake Jan 21 '14 at 11:45
@PeterWestlake I'm fully aware of this. But the question is highly unclear. The word *digit* is not present in the question. – Sven Hohenstein Jan 21 '14 at 11:45
@SvenHohenstein Agreed that it's unclear (should be closed unless / until clarified), but "alphanumeric" does appear in the question, which `a!` isn't. – Bernhard Barker Jan 21 '14 at 11:51
@Dukeling Right, but `11` is alphanumeric *and* invalid. – Sven Hohenstein Jan 21 '14 at 11:52

score 0 · Answer 4 · answered Jan 21 '14 at 11:47

0

You can use :

^.*([a-zA-Z]{2}|(\d[a-zA-Z])|([a-zA-Z]\d))$

DEMO

EXPLANATION:

enter image description here

answered Jan 21 '14 at 11:47

Sujith PS

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validating last two characters to follow a pattern

4 Answers4