[bug #21199] odd output for some patterns combining backreference, alternation, and repetition

[Alex Lamey]

URL:
  <http://savannah.gnu.org/bugs/?21199>

                 Summary: odd output for some patterns combining
backreference, alternation, and repetition
                 Project: grep
            Submitted by: lexlamey
            Submitted on: Sunday 09/30/2007 at 20:03
                Category: None
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

I think grep (2.5.1) is misbehaving on me.  Here are twelve examples, wherein
I apply six patterns (differing only in the repetition argument) to two inputs
(differing only in their fifth character).  Five of the outputs (marked '!')
seem to be wrong to me.  But I'm quite new to grep so maybe I've misunderstood
something.

$ echo 88-88 | egrep -o '([0-9])([0-9])-(\1|\2){1}'
88-8

$ echo 88-88 | egrep -o '([0-9])([0-9])-(\1|\2){2}'
88-88

$ echo 88-88 | egrep -o '([0-9])([0-9])-(\1|\2){3}'
88-88
    !

$ echo 88-88 | egrep -o '([0-9])([0-9])-(\1|\2){4}'
88-8
    !!

$ echo 88-88 | egrep -o '([0-9])([0-9])-(\1|\2){5}'
88-88
    !

$ echo 88-88 | egrep -o '([0-9])([0-9])-(\1|\2){6}'
88-88
    !

$ echo 88-81 | egrep -o '([0-9])([0-9])-(\1|\2){1}'
88-8

$ echo 88-81 | egrep -o '([0-9])([0-9])-(\1|\2){2}'
88-8
    !

$ echo 88-81 | egrep -o '([0-9])([0-9])-(\1|\2){3}'

$ echo 88-81 | egrep -o '([0-9])([0-9])-(\1|\2){4}'

$ echo 88-81 | egrep -o '([0-9])([0-9])-(\1|\2){5}'

$ echo 88-81 | egrep -o '([0-9])([0-9])-(\1|\2){6}'





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