So you want to match: C1234_.IDX, C1234_45.IDX and C1234.IDX but not C1234ABC.IDX. Is this correct?

If so, the pattern could be something like this :

/^([cljso]\d{4}(_\d*)?\.(dat|idx))$/

i.e. start of string, one of the five letters cljso, 4 digits, an optional ("_" followed by any number of digits), followed by a dot and an extension chosen among dat and idx at the end of the string.

If this is not what you need, please be clearer on your requirement.

In reply to Re: Regular Expression Assistance by Laurent_R
in thread Regular Expression Assistance by jaacmmason

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