Le Tuesday 11 November 2008 21:47:55 Ian Hilt, vous avez écrit :
> On Tue, 11 Nov 2008, Francis Galiegue wrote:
> > Le Tuesday 11 November 2008 02:49:19 Tait, vous avez écrit :
> > > > > > + if ($c_file =~ /^To:\s*+(.+)\s*\nCc:/ism) {
> > > > >
> > > > > Greedy operators are only supported with perl 5.10 or more... I
> > > > > think it's a bad idea to use them...
> > > >
> > > > The problem here was that a space should follow the field, but it may
> > > > not. The user may unwarily backup over it. "\s*" would match this
> > > > case.
> > > >
> > > > But if there is a space, it is included in the "(.+)".
> > >
> > > Not in any version of Perl to which I have access.
> >
> > And if you see a space in (.+), your regex engine is buggy anyway.
>
> So what does this script produce on your systems?
>
>
> #!/usr/bin/perl -Tw
> --8<--
> use strict;
> my $ws = "To: \nCc:";
>
> $ws =~ /^To:\s*(.+)\s*\nCc:/ism;
>
> if ($1 eq ' ') {
> print "\$1 is equal to a space.\n";
> }
> -->8--
>
> On mine, it prints the message. So it seems it is matching _a_ space.
Which is perfectly normal. The first \s* wanted spaces, it got them. But it
left nothing for the capturing .+ behind. And any quantifier (except when it
is possessive) _MUST_ backtrack in order for the full regex to complete. This
is why the .+ captured the space: the first \s* was perfectly fine with no
space at all, and the second, well, didn't find any space but it didn't care
either.
--
Francis Galiegue
ONE2TEAM
Ingénieur système
Mob : +33 (0) 6 83 87 78 75
Tel : +33 (0) 1 78 94 55 52
fge@xxxxxxxxxxxx
40 avenue Raymond Poincaré
75116 Paris
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