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Groups > gnu.bash.bug > #15406

Re: Regular Expression matching operation =~

From Grisha Levit <grishalevit@gmail.com>
Newsgroups gnu.bash.bug
Subject Re: Regular Expression matching operation =~
Date 2019-09-23 01:01 -0400
Message-ID <mailman.828.1569214911.2190.bug-bash@gnu.org> (permalink)
References <slrnqofqq2.43b.trepidation@vps.jonz.net> <CAMu=Bro6fMaj=0p+kF1WM34=8J3KHWduVi7Qhwcfp=YSVQVPfw@mail.gmail.com>

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On Sun, Sep 22, 2019 at 9:02 PM Allodoxaphobia <trepidation@example.net> wrote:
>
> In moving a bash ver. 4.3.48 (Ubuntu) program to a bash ver. 5.0.11
> (FreeBSD) environment I encountered either a bug, a quirk, or
> an undocumented feature.
>
> I was using a null regexp as a "match for anything" case

This behavior depends on the OS's underlying regex implementation.
For example BSD says (man 3 regex, under IMPLEMENTATION CHOICES):

    An empty parenthesized subexpression, `()', is legal and matches an empty
    (sub)string.  An empty string is not a legal RE.

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Re: Regular Expression matching operation =~ Grisha Levit <grishalevit@gmail.com> - 2019-09-23 01:01 -0400

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