Thanks for the reply. I was wrong in my report. It does match values like aab and aaaaaab in its original form.
What is wrong is the description `zero or one instances of 'a''. But if we correct the right hand side word to be `[[:space:]]*(a)?b' that it does match what the description says.(the parenthese around `a' could be omitted). I was also wrong saying it was a pattern instead of a regular expression. It is syntatically correct as a regular expression. A word can be syntactically correct as a pattern and a regular expression at the same time though the semantic might be different in most cases. On Fri, Sep 20, 2019 at 11:48 PM Chet Ramey <chet.ra...@case.edu> wrote: > On 9/20/19 1:40 AM, hk wrote: > > > Bash Version: 5.0 > > Patch Level: 0 > > Release Status: release > > > > Description: > > On section 3.2.4.2 of Bash Reference Manual, the example on* > > [[...]]* (page 13 in the PDF) is incorrect. Specifically, the example > say *[[ > > $line =~ [[:space:]]*?(a)b ]]* will match values like *'aab'* and* > > 'aaaaaab*'. But it won't. The operator is* =~*, but the operand on the > > right side is a pattern while it should be a regular expression. > > Thanks for the report, this is a good catch. It's been this way since 2011. > > It's supposed to be a regular expression, and there's a typo. You're right > that it doesn't match the same things as if it were interpreted as a shell > pattern. > > The pattern would match the description if it were `[[:space:]]*(a)?b'. > > The pattern, once corrected, does match the strings in the example below, > since, as the description says, it matches "a sequence of characters in the > value." > > The regexp is unanchored, though you can anchor it yourself. That's > arguably less useful than the anchored case (like, say, grep), but that's > what you get from regcomp/regexec, and you have $BASH_REMATCH to see what > you matched. > > Chet > > -- > ``The lyf so short, the craft so long to lerne.'' - Chaucer > ``Ars longa, vita brevis'' - Hippocrates > Chet Ramey, UTech, CWRU c...@case.edu http://tiswww.cwru.edu/~chet/ >
