Re: Bash parameter expansion (remove largest trailing match, remove largest leading match, pattern replacement) does not work

[Lawrence Velázquez]

> On Aug 29, 2020, at 8:41 PM, Bruce Lilly <bruce.lilly@gmail.com> wrote:
> 
>> On Sat, Aug 29, 2020 at 4:53 PM Koichi Murase <myoga.murase@gmail.com> wrote:
>> 
>> Yes, I know that it is confusing to those who are familiar with modern
>> Perl-style regular expressions.  But historically, POSIX regular
>> expressions do not support the backslash escape sequences in bracket
>> expressions `[...]'.  The backslash escape sequences in bracket
>> expressions were the extension historically.  As far as I know, in
>> POSIX, only awk supports backslash sequences in regular expressions.
> 
> Actually, it works (portably) with
> separator2=$'\057'

(a) $'...' is not POSIX. For instance, dash does not recognize it.

        % port installed dash
        The following ports are currently installed:
          dash @0.5.11.1_0 (active)
        % dash <<\EOF
        heredoc> printf '<%s>\n' $'\057'
        heredoc> EOF
        <$\057>

(b) If you define separator2 in that way and then substitute it,
    the context into which it is substituted sees a slash character,
    not the backslash-escaped octal.

        $ echo "$BASH_VERSION"
        5.0.17(1)-release
        $ printf '%s\n' $'\057'
        /

vq