grarpamp at gmail.com
Tue Sep 27 02:34:18 UTC 2011
Under the ERE implementation in RELENG_8, I'm having
trouble figuring out how to group and backreference this.
Given a line, where:
If AAA is present, CCC will be too, and B may appear in between.
If AAA is not present, neither CCC or B will be present.
DDDD is always present.
Junk may be present.
Match good lines and ouput in chunks.
echo junkAAAABCCCDDDDjunk | \
This works as expected:
sed -E -n 's,^.*(AAAB?CCC)(DDDD).*$,1 \1 2 \2,p'
1 AAABCCC 2 DDDD
But making the leading bits optional per spec does not work:
sed -E -n 's,^.*(AAAB?CCC)?(DDDD).*$,1 \1 2 \2,p'
1 2 DDDD
Nor does adding the usual grouping parens:
sed -E -n 's,^.*((AAAB?CCC)?)(DDDD).*$,1 \1 2 \2,p'
How do I group off the leading bits?
Or is this a limitation of ERE's?
Or a bug?
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