Re: RS='.^' apparently ignores the RS setting

[Ed Morton]

Response below...

On 7/13/2021 6:46 AM, arnold@skeeve.com wrote:
> Hi.
>
> Ed Morton <mortoneccc@comcast.net> wrote:
>
> > So I read
> > https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04_09
> > which I thought was saying you could use any character before the `^`
> > and it wouldn't match which was supported by this test:
> >
> >       $ printf 'ax^b\nax^b\n' | awk 'BEGIN{RS="x^"}{print NR, $0}'
> >       1 ax^b
> >       ax^b
> >
> > but then I can't explain this where gawk is apparently completely
> > ignoring the RS setting:
> >
> >       $ printf 'a.^b\na.^b\n' | awk 'BEGIN{RS=".^"}{print NR, $0}'
> >       1 a.^b
> >       2 a.^b
> >
> > Is that a bug?
> No. ^ and $ are always metacharacters in EREs, even if that means
> you can create nonsense regexps. You have to escape them to get
> them to be treated literally:
>
> $ printf 'ax^b\nax^b\n' | ./gawk 'BEGIN{RS="x\\^"}{print NR, $0}'
> 1 a
> 2 b
> a
> 3 b
>
> $ printf 'a.^b\na.^b\n' | ./gawk 'BEGIN{RS=".\\^"}{print NR, $0}'
> 1 a
> 2 b
> a
> 3 b
>
> HTH,
>
> Arnold

I understand now that they are metachars in a ERE and I don't want them 
treated literally in this case.

The question is - why, given `RS='.^'` (a regexp that cannot match 
anywhere in the input), does gawk seem to ignore the RS and act as if I 
had `RS='\n'` when given `RS='x^'` (a different but similar regexp that 
also cannot match anywhere in the input) awk just reads the whole input 
in at once as you'd expect it to given a regexp that doesn't match the 
input?

$ printf 'ax^b\nax^b\n' | gawk 'BEGIN{RS="x^"}{print NR, $0}'
1 ax^b
ax^b

$ printf 'a.^b\na.^b\n' | gawk 'BEGIN{RS=".^"}{print NR, $0}'
1 a.^b
2 a.^b

Regards,

    Ed.