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Re: devel: Questions about quoting in the new replacement ${var/pat/&}

From: Koichi Murase
Subject: Re: devel: Questions about quoting in the new replacement ${var/pat/&}
Date: Wed, 19 Jan 2022 10:50:08 +0900

Thank you for your consideration and for implementing it.  I have
tried the latest devel branch and played with it.  I now really like
its behavior.  Thank you very much for taking it into consideration.

> I generally make new functionality that's controlled by a separate option
> off by default in releases. I'll do the same here. It's on now so we can
> evaluate its effects. It's hard to get enough people to test alpha and
> beta releases, so who knows what good that will do.

I see, I have not noticed it.  Thank you for your explanation and
sorry for the noise.

> It probably won't be in bash-5.2-alpha, since I already froze and tested
> that, but the behavior will be different in the next devel branch push
> after that.

Does that mean it will be in bash-5.2-beta or in bash-5.3?  I am
interested in what would be the behavior of the release version of
bash-5.2, which would affect how I will modify my script.

> I still like the simpler explanation: if bash-5.1 expanded `string' to
> something that contained an unescaped `&', replace it. If it expanded to
> something that contained a literal '\&' you'll get a `&'. Backslash-escaped
> backslashes produce a single literal backslash. But allowing double quotes
> to inhibit the replacement is probably better for backwards compatibility,
> even with patsub_replacement off by default.

Is this an explanation that will be put in ChangeLog or in Bash
Reference Manual?  I have checked how the quoting of anchor
characters, # and %, in ${var/#prefix} and ${var/%suffix} is explained
in Bash Reference Manual but could not find the mention about the
quoting.  For the pattern matching operators, I found an explanation:

> From https://www.gnu.org/software/bash/manual/html_node/Pattern-Matching.html:
> [...] The special pattern characters must be quoted if they are to
> be matched literally.

but I feel the detailed behavior is actually not so clear from this


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