Re: dash bug: double-quoted "\" breaks glob protection for next char

[Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>]

On Wed, Apr 04, 2018 at 01:56:42PM +0200, Denys Vlasenko wrote:
>
> This is the example which is not affected by echo differences:
> 
> cat <<EOF
> -\"-\'-\`-\--\z-\*-\?-
> `echo  '-\"-\x-\`-\--\z-\*-\?-'`
> $(echo '-\"-\x-\`-\--\z-\*-\?-')
> EOF
> 
> # bash z
> -\"-\'-`-\--\z-\*-\?-
> -\"-\x-`-\--\z-\*-\?-
> -\"-\x-\`-\--\z-\*-\?-
> # dash z
> -\"-\'-`-\--\z-\*-\?-
> -"-\x-`-\--\z-\*-\?-
> -\"-\x-\`-\--\z-\*-\?-
> 
> IOW: if `cmd` outputs \" in here document, it is converted to "
> whereas bare \" in here document is passed verbatim as \", and
> $(cmd) in here document also does not show this.
> 
> Aha... I think `` in heredocs removes \ in commands before
> running them. Thus, `echo  '\"'` would run: echo '"'
> 
> http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_03
> "Within the backquoted style of command substitution, <backslash>
> shall retain its
> literal meaning, except when followed by: '$', '`', or <backslash>"
> 
> I think it should retain \" as \".

It wasn't the backquote that removed the backslash but the here-
document.  This is expected behaviour as here-documents behave
like double quotes so the backslash is indeed special when it
precedes a double quote.

As I said ksh93 does the same thing.

Cheers,
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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