I have a regex that gives me one result in sed but another in Perl (and Ruby).
I have the string one;two;;three and I want to highlight the substrings delimited by the ;. So I do the following in Perl:
$a = "one;two;;three";
$a =~ s/([^;]*)/[\1]/g;
print $a;
(Or, in Ruby: print "one;two;;three".gsub(/([^;]*)/, "[\\1]").)
The result is:
[one][];[two][];[];[three][]
(I know the reason for the spurious empty substrings.)
Curiously, when I run the same regexp in sed I get a different result. I run:
echo "one;two;;three" | sed -e 's/[^;]*/[\0]/g'
and I get:
[one];[two];[];[three]
What is the reason for this different result?
EDIT:
Somebody replied "because sed is not perl". I know that. The reason I'm asking my question is because I don't understand how sed copes so well with zero-length matches.