Regular Expression for a string

[Teja]

Roy Smith wrote:

> In article <1162440285.962155.325540 at f16g2000cwb.googlegroups.com>,
>  "Teja" <tejovathi.p at gmail.com> wrote:
>
> > HI all,
> >
> > I need to write a regular experssion for a string which satisfies the
> > following a criteria :
> >
> > 1) it should start with an alphabet
>
> I assume you mean, "It should start with a letter"?
>
> > 2) it can contain alphabets/digits/_ from second character
> > 3) it can contain "[a-z]" or "[0-9]" at the end. but this is optional
>
> How about:  ^[a-zA-Z][a-zA-Z0-9_]*[a-z0-9]?$
>
> Probably many variations on that theme will also work.

Thnks Roy for ur quick reply.....
Here is what I want actually

Some examples

string1
string_1
string1[0]
string_1_str[a]
STRING_1_[2]
STRING_1_str[a][1][2]

etc
etc

I need a regular expression for such strings