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grep backreferencing question

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# 22  
Old 10-19-2010
How is that worthless? It means that back references are probably universally supported in grep, but not in egrep (grep -E).. . From the Solaris regex man page:

Quote:
The rules specififed for BREs apply to Extended Regular Expressions
(EREs) with the following exceptions:

[..]
o The back reference operator is not supported
# 23  
Old 10-20-2010
OpenBSD's Manual Pages: re_format(7) also makes it clear that the "back-reference" is specific to BREs.
# 24  
Old 10-20-2010
Worthless as a mnemonic for a good concept, mental model of how regex works, which is forward, in pieces, iteratively for every variable piece from longest to shortest.
# 25  
Old 10-20-2010
I disagree. The term is widely used and understood. If anything, I find the term "back-reference" to be quite intuitive; it's a reference that points back to an earlier element of the same regular expression.

If anything is worthless, it's the term "regular expression" itself. With all the different flavors floating around (posix BRE, posix ERE, pcre, perl, emacs, vi, vim, nvi, etc), they're highly irregular.

Regards,
Alister
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