Re: Is ":G" of ${name:s/l/r/:G} actually supported?

["Mark J. Reed" <markjreed@gmail.com>]

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>
        In addition to the following operations, the colon modifiers
        described in the section `Modifiers' in the section `History
        Expansion' can be applied: for example, ${i:s/foo/bar/}
        performs string substitution on the expansion of parameter $i.

That's a very helpful snippet that I missed. Thanks. Sorry for the
misinformation.


On Mon, Feb 12, 2024 at 4:52 PM Lawrence Velázquez <larryv@zsh.org> wrote:

> On Mon, Feb 12, 2024, at 12:11 PM, Mark J. Reed wrote:
> > Well, that was a shorter reply than I intended. But you should be able
> > to see that the section you linked (14.1.4 Modifiers) is part of 14.1,
> > History Expansion. Those modifiers don't apply to parameter
> > substitution.
>
> They do.
>
>         % var=foobar
>         % print -- $var:s/o/x
>         fxobar
>
> This is documented in zshexpn(1) under "Modifiers":
>
>         After the optional word designator, you can add a sequence
>         of one or more of the following modifiers, each preceded
>         by a `:'.  These modifiers also work on the result of
>         _filename generation_ and _parameter expansion_, except
>         where noted.
>
> and "PARAMETER EXPANSION":
>
>         In addition to the following operations, the colon modifiers
>         described in the section `Modifiers' in the section `History
>         Expansion' can be applied: for example, ${i:s/foo/bar/}
>         performs string substitution on the expansion of parameter $i.
>
>
> > For doing replacements with parameter expansion, you can just use the
> > slash modifier. One / replaces the first occurrence, two //s does all
> > of them:
> >
> >> *$ value=/dir/subdir/file.csv*
> >> *$ echo ${value//dir/_G}*
> >> */_G/sub_G/file.csv*
> >
> > That's not a zsh-specific feature; ksh and bash have it as well. Zsh
> > likely has a different mechanism to accomplish the same thing, but I've
> > not needed it so am not familiar with it.
>
> The :s and :gs history modifiers are similar but not exactly so.
> Among other things, they perform literal searches by default, allow
> referring to the matched text with "&", and apply nested expansions
> differently.
>
>
> >> On Mon, Feb 12, 2024 at 9:19 AM Joachim Ansorg <mail@bashsupport.com>
> wrote:
> >>> Hi,
> >>> I was reading about modifiers on page
> >>> https://zsh.sourceforge.io/Doc/Release/Expansion.html#Modifiers,
> which says:
> >>>
> >>> >   The forms ‘gs/l/r’ and ‘s/l/r/:G’ perform global substitution,
> i.e. substitute every occurrence of r for l. Note that the g or :G must
> appear in exactly the position shown.
> >>>
> >>> But zsh 5.9 doesn't seem to support this:
> >>>   > value="/dir/subdir/file.csv"
> >>>   > echo ${value:s/dir/_/:G}
> >>>   zsh: unrecognized modifier `G'
>
> It doesn't work on zsh 4.3.11 either, which means it hasn't worked
> for at least 13 years.  (This probably says something about the
> prevalence of applying :s/l/r/:G to parameter expansions.)
>
>
> >>> Is ":G" actually supported or is the documentation outdated here?
>
> I can't say for sure, but this feels like a bug to me.
>
>
> --
> vq
>


-- 
Mark J. Reed <markjreed@gmail.com>

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