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Re: is expr's \? regex metachar working?
From: |
Clark Morgan |
Subject: |
Re: is expr's \? regex metachar working? |
Date: |
Thu, 23 Aug 2001 08:11:54 -0700 |
User-agent: |
Mutt/1.2.5i |
On Thu, Aug 23, 2001 at 05:05:46PM +0200, Andreas Schwab wrote:
> Clark Morgan <cmorganOaracnet.com> writes:
>
> |> On Thu, Aug 23, 2001 at 04:47:31PM +0200, Andreas Schwab wrote:
> |> > ???? The regexp _is_ matching, since expr prints > 0.
> |>
> |> $ ./expr "abcdef" : '.*b'
> |> 2
> |> $ ./expr "abcdef" : '.*b\+'
> |> 2
> |> $ ./expr "abcdef" : '.*b\?'
> |> 6
> |>
> |> Does this illustrate why I think it's broken?
>
> No, not at all.
>
> |> Remember, the docu says: 0 or 1 matches. It seems to me that \?
> |> matches 0 occurrences always.
>
> Be carefull with such a statement, you have to check *all* cases, but a
> single couterexample is enough to prove the opposite:
>
> $ expr "abcdef" : 'a\?bcd'
> 4
>
> You can only look at a regexp as a whole, context matters.
But, and this is a big BUT, expr puts an implied '^' at the beginning of
every regexp. Consequently, when matching a nontrivial pattern, you've got
no choice but to add .* at the beginning of the regexp if you want to find
a substring.
- is expr's \? regex metachar working?, Clark O. Morgan, 2001/08/23
- Re: is expr's \? regex metachar working?, Andreas Schwab, 2001/08/23
- Re: is expr's \? regex metachar working?, Clark Morgan, 2001/08/23
- Re: is expr's \? regex metachar working?, Andreas Schwab, 2001/08/23
- Re: is expr's \? regex metachar working?, Clark Morgan, 2001/08/23
- Re: is expr's \? regex metachar working?, Andreas Schwab, 2001/08/23
- Re: is expr's \? regex metachar working?,
Clark Morgan <=
- Re: is expr's \? regex metachar working?, Andreas Schwab, 2001/08/23
- Re: is expr's \? regex metachar working?, Clark Morgan, 2001/08/23
- Re: is expr's \? regex metachar working?, Paul Jarc, 2001/08/23
Re: is expr's \? regex metachar working?, Clark O. Morgan, 2001/08/23