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

[Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx>]

On Wed, Apr 4, 2018 at 5:13 PM, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> 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.

This does not match what happens with this simple heredoc:

cat <<EOF
\"
EOF

# dash zz
\"
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