From: Jilles Tjoelker <jilles@stack.nl>
To: "G.raud" <graud@gmx.com>
Cc: dash@vger.kernel.org
Subject: Re: [BUG] quoted substring parameter expansion ignores single-quotes in the arg
Date: Sat, 21 Oct 2017 14:13:43 +0200 [thread overview]
Message-ID: <20171021121343.GA29646@stack.nl> (raw)
In-Reply-To: <20171019104103.7gzflupyi27artlg@gmx.com>
On Thu, Oct 19, 2017 at 12:41:30PM +0200, G.raud wrote:
> Wrong bug report.
> In fact the beahviour of dash on "a=\\'a\\'; echo \"\${a%'}\"" is that
> of POSIX and of zsh 5. However 'bash --posix', 'mksh -o posix' and
> pdksh fail to parse the command and ksh does not remove the quote from
> $a.
I think your original bug report is actually valid. Although the POSIX
standard may be hard to interpret (make sure to use the latest (2016)
edition), I think it is sufficiently clear that various special
characters are active in ${param#word}, whether the outer substitution
is within double-quotes or not. See this sentence in 2.6.2 Parameter
Expansion:
] Enclosing the full parameter expansion string in double-quotes shall
] not cause the following four varieties of pattern characters to be
] quoted, whereas quoting characters within the braces shall have this
] effect.
More generally, if bash --posix and ksh93 agree about something, it is
usually correct (use something like "${a#'*'}", since "${a#'}" is
wrong). Although zsh is a good interactive shell, it does not follow
POSIX as closely; not even in sh or ksh emulation mode.
Also note that dash does implement this correctly if a metacharacter is
quoted using a single-quote or a backslash:
$ v=**
$ echo "${v#*}"
**
$ echo "${v#"*"}"
*
$ echo "${v#\*}"
*
In dash's internals, this bug is caused by not distinguishing between
+/-/=/? and #/##/%/%% varieties in the parser. Not maintaining state for
eacg nesting level makes the parser more elegant, but it is untenable
since there is no way one can parse both "${v+'}" and "${v#'*'}"
correctly without it.
--
Jilles Tjoelker
next prev parent reply other threads:[~2017-10-21 12:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-26 3:41 [BUG] quoted substring parameter expansion ignores single-quotes in the arg G.raud
2017-10-19 10:41 ` [NO-BUG] " G.raud
2017-10-21 12:13 ` Jilles Tjoelker [this message]
2017-10-25 10:08 ` [BUG] " Martijn Dekker
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20171021121343.GA29646@stack.nl \
--to=jilles@stack.nl \
--cc=dash@vger.kernel.org \
--cc=graud@gmx.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).