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Re: Inconsistent quote and escape handling in substitution part of param


From: Chet Ramey
Subject: Re: Inconsistent quote and escape handling in substitution part of parameter expansions.
Date: Tue, 28 Feb 2012 16:05:14 -0500
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:8.0) Gecko/20111105 Thunderbird/8.0

On 2/28/12 12:26 PM, John Kearney wrote:

> But that isn't how it behaves.
> "${test//str/"dddd"}"
> 
> because str is replaced with '"dddd"' as such it is treating the double
> quotes as string literals.
> 
> however at the same time these literal double quotes escape/quote a
> single quote between them.
> As such they are treated both as literals and as quotes as such
> inconsistently.

I don't have a lot of time today, but I'm going to try and answer bits
and pieces of this discussion.

Yes, bash opens a new `quoting context' (for lack of a better term) inside
${}.  Posix used to require it, though after lively discussion it turned
into "well, we said that but it's clearly not what we meant."

There are a couple of places in the currently-published version of the
standard, minus any corregendia, that specify this.  The description of
${parameter} reads, in part,

"The matching closing brace shall be determined by counting brace levels,
skipping over enclosed quoted strings, and command substitutions."

The section on double quotes reads, in part:

"Within the string of characters from an enclosed "${" to the matching
'}', an even number of unescaped double-quotes or single-quotes, if any,
shall occur."

Chet
-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/



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