Re: grep: echo -en "AB\nA B\n" | egrep 'A?B'

[p.p.]

> "p.p." <address@hidden> wrote:
> > if I do
> >
> > echo -en "AB\nA B\n" | egrep 'A?B'
> >
> > the result is
> > AB
> > A B
> >
> > while, as I understand it, the second line containing the space should not 
> > match.
> 




--- John Cowan <address@hidden> schrieb:
> The latter.
> 
> Your pattern says to match an optional A followed by a B.  The first
> line has an A followed by a B, so it matches; the second line has a B,
> so it too matches.  The presence of an A on the second line is irrelevant.
> 
> You may want to wrap your pattern in ^ and $ to force it to match the
> whole line.
> 



--- Paul Jarc <address@hidden> schrieb:
> The regexp will match any line that contains "AB" or "B".  If you want
> to match only those lines that are exactly "AB" or "B", with nothing
> else surrouding them, then you have to add beginning- and end-of-line
> anchors:
> egrep '^A?B$'
> 
> Also, you might want to use "grep -E" insteead of "egrep", for the
> sake of portability - only "grep -E" is specified by POSIX.
> 
> 
> paul
> 



ouch, ok, I feel ashamed - you're right.
Actually I had a leading '^'.
I try to reproduce my problem when I'm back on the other computer and in the 
meantime I make a
note to not create minimal examples after 10pm.

peter

@paul: thanks for the "-E" hint, I was always wondering which way is more right.



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