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Re^5: Regex's, parentheses, and the mysterious ( ??{ } ) operator

by AnomalousMonk (Canon)
on Jul 12, 2013 at 18:00 UTC ( #1044042=note: print w/replies, xml ) Need Help??

in reply to Re^4: Regex's, parentheses, and the mysterious ( ??{ } ) operator
in thread Regex's, parentheses, and the mysterious ( ??{ } ) operator

... our is our

I think Anonymonk is concerned about the second appearance of  our $re within the  (??{ our $re }) regex subexpression. Although somewhat unfamiliar, I think this is kosher because our acts as a declaration of a package variable and  $re needs to be declared or pre-declared somehow to be referenced within the regex under full strictures. The following variations work identically with strictures (note no capturing groups within $re):

>perl -wMstrict -le "my $s = 'x(y) (a(b)) ()() q (a(b)c()(d(e(f)g))h) q'; ;; our $r3; $r3 = qr{ \( (?: [^()]+ | (??{ $r3 }) )* \) }xms; ;; my @p = $s =~ m{ $r3 }xmsg; print qq{'$_'} for @p; print '--------'; ;; $s =~ m{ ($r3) [^()]* ($r3) }xms; print qq{1 '$1' 2 '$2'}; print '--------'; " '(y)' '(a(b))' '()' '()' '(a(b)c()(d(e(f)g))h)' -------- 1 '(y)' 2 '(a(b))' --------

And the OPed:

our $r3 = qr{ ... (??{ our $r3 }) ... }xms;

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[Corion]: Maybe doing a double-fork (daemonizing) can make go that information away, but maybe not
[Corion]: But I think my knowledge of unix/Linux datastructures is several decades out of date, so I don't really know what information it keeps on processes
[oiskuu]: The useful bits that relate to your process can be found under /proc/self. What information are you thinking of? Tty name?
[tye]: I just daemonized and getlogin() still knew who I had been.
[tye]: perhaps loginuid ? Not that I concede that something not being in /proc means it is not useful.
[Corion]: tye: That's really interesting, but maybe it is because getlogin() returns the name, or the uid, so if that user has been replaced by another user with the same uid in the meantime, that's no problem to the system...
[davido]: or on ubuntu /var/run/utmp
[Corion]: Otherwise, I would imagine that a user with a process still alive would lock that information in memory.
[davido]: so last -f /var/run/utmp on ubuntu provides similar (though more verbose) info

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