Re: GNU grep back references

[Jan Schampera]

On Mon, 10 Oct 2005 12:59:46 +0100
Julian Foad <address@hidden> wrote:

> paragraph from section 9.2:
> 
>    "[...]  Some utilities employing regular expressions limit the 
> processing to lines; [...]. Those utilities (like grep) that do not 
> allow <newline>s to match are responsible for eliminating any
> <newline> from strings before matching against the RE.  [...]"
> 
>  From the Single UNIX Specification v2 Grep page 
> <http://www.opengroup.org/onlinepubs/007908799/xcu/grep.html>,
> Description, second paragraph:
> 
>    "[...] since patterns are matched against individual lines of the
>    input [...]"
I looked at grep description for that, but it seems i didn't look for
the right keywords. Excuse that. This paragraph specifies it very clear.

> It seems that SVR4's Grep, if it is intentionally treating the whole
> input as one long string, is in any case wrongly taking the
> back-reference to refer to the _first_ string matched by the
> subexpression.
With my new information I fully agree with that.

We found that behaviour by some user asking for matching numbers like
used in my example, and we couldn't find a clear answer which behaviour
the standard-writers *expected*.

> I hope this helps and shows that GNU Grep is doing the right thing.
See above.
Also, to clarify that: It wasn't meant as "GNU grep is wrong", if it
sounded like that.

Thanks a lot for this extended answer,
Jan

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