http://qs321.pair.com?node_id=1229800

morgon has asked for the wisdom of the Perl Monks concerning the following question:

Hi,

I am trying to construct a regex that extracts the string beween two quotes with the complication that that string may contain backslash-escaped quotes.

To illustrate:

my $rexeg = ???? # this is what I am after

my ($m1) = '"hubba bubba"' =~ $regex;
print "ok\n" if $m1 eq 'hubba bubba';   # should print "ok"

my ($m2) = '"hubba \"bubba\""' =~ $regex;
print "ok\n" if $m2 eq 'hubba "bubba"';   # should also print "ok"

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I hope that is understandable...

I tried to do this with negative lookbehinds, but I attempt failed with "Variable length lookbehind not implemented", so am looking for some help here.

Many thanks!

Replies are listed 'Best First'.
Re: regex for strings with escaped quotes
by haukex (Archbishop) on Feb 12, 2019 at 15:13 UTC 
    use Regexp::Common qw/delimited/;

my $str = q{ x "foo \"bar\"" y };
$str =~ /($RE{delimited}{-delim=>'"'})/;
print $1, "\n";

print $RE{delimited}{-delim=>'"'}, "\n";

__END__

"foo \"bar\""
(?:(?|(?:\")(?:[^\\\"]*(?:\\.[^\\\"]*)*)(?:\")))

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[d/l]
      It somehow stops working when I use the regex directly and I cannot see why: 
      my $str = q{ x "foo \"bar\"" y };
$str =~ /(?:(?|(?:\")(?:[^\\\"]*(?:\\.[^\\\"]*)*)(?:\")))/;
print $1, "\n";

# prints nothing

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[d/l]
        $str =~ /(?:(?|(?:\")(?:[^\\\"]*(?:\\.[^\\\"]*)*)(?:\")))/;

        It's missing the capture group that I added: /($RE{delimited}{-delim=>'"'})/

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      thanks, but I forgot to mention one detail:

      I do not need this for a perl-program but for a perl5-compatible regex engine in Go.

      I there a way to print the regex that is used?

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        I there a way to print the regex that is used?

        That's what the second line of output above is. Simplification of that regex is left as an exercise to the reader :-) (Update: Nevermind.)

        BTW, you can also use the -keep feature to get only the part between the quotes:

        use Regexp::Common qw/delimited/;
q{ x "foo \"bar\"" y } =~ /$RE{delimited}{-delim=>'"'}{-keep}/;
print $3, "\n";  # prints: foo \"bar\"

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