From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from vulcan.kevinlocke.name (vulcan.kevinlocke.name [107.191.43.88]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5585A29ACE5 for ; Mon, 20 Oct 2025 20:18:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=107.191.43.88 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760991526; cv=none; b=WjDlGb/3q6FSfubwtBOcGWLSr4beCX2yZrAVau8g/JDOITft/pzWUJ3l1Q7HF8yWOLGZCVJSh2ksDYuGJQSuhnOtb3/cBC5leKBbVZW6I0CkXeTb88SDHfR06PgBznnMfrT6tE4KHFvufO3kkVS7Ti3pnHXq0vpWBuJmH9Y+Tvg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760991526; c=relaxed/simple; bh=mRsspvS4GSDk7FCyLt6d8jksX0zrgFXWBP1p98LUeJ4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HZi3PramNlsEUMCceLdKniFnEdWefYGIPlYcJzPrSoShASkv/QMCQsLGfJrEMLyejj4mqjsWEcGgUclsHvI7hsy0bnTzIQqh9O+NBZcvjSSeqhWIOJf41OxskVZW+rULJ3a6di3oLrRWiORecXNWr1f7JuoF7PotWfM8NqjDXdI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=kevinlocke.name; spf=pass smtp.mailfrom=kevinlocke.name; arc=none smtp.client-ip=107.191.43.88 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=kevinlocke.name Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kevinlocke.name Received: from kevinolos.kevinlocke.name (unknown [198.60.113.91]) (Authenticated sender: kevin@kevinlocke.name) by vulcan.kevinlocke.name (Postfix) with ESMTPSA id 8EB484562BC5; Mon, 20 Oct 2025 20:18:34 +0000 (UTC) Received: by kevinolos.kevinlocke.name (Postfix, from userid 1000) id 7D14713001C9; Mon, 20 Oct 2025 14:18:32 -0600 (MDT) Date: Mon, 20 Oct 2025 14:18:32 -0600 From: Kevin Locke To: David Laight Cc: Jonathan Corbet , Randy Dunlap , Thorsten Leemhuis , linux-kernel@vger.kernel.org Subject: Re: [PATCH] tools: remove unnecessary x suffix in test strings Message-ID: Mail-Followup-To: Kevin Locke , David Laight , Jonathan Corbet , Randy Dunlap , Thorsten Leemhuis , linux-kernel@vger.kernel.org References: <20251016214707.5c3d373b@pumpkin> <20251017151256.111f2669@pumpkin> <20251019111748.3d5ac8d9@pumpkin> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251019111748.3d5ac8d9@pumpkin> On Sun, 2025-10-19 at 11:17 +0100, David Laight wrote: > On Fri, 17 Oct 2025 16:28:12 -0600 Kevin Locke wrote: >> On Fri, 2025-10-17 at 15:12 +0100, David Laight wrote: >>> On Thu, 16 Oct 2025 17:47:09 -0600 Kevin Locke wrote: >>>> Remove the "x" suffixes which unnecessarily complicate the code. >>> >>> The problems arise when $1 is (say) "-x", a simple LR parser will treat >>> [ -x = -x ] as a check for the file "=" being executable and then give >>> a syntax error for the second -x. >>> I can't imagine why shellcheck should warn about a leading x (or any other >>> character) provided field splitting is disabled (eg by ""). >>> The leading x has definitely been needed in the past. >> >> Yep, it definitely has been. The rationale on the wiki is that it's >> not necessary for modern shells (and presumably that it unnecessarily >> complicates the code): https://www.shellcheck.net/wiki/SC2268 >> However, it notes Zsh had issues as recently as 2015, which is not as >> old as I would have expected. > > It doesn't really make much difference to the shell. > I really doubt you'll notice any difference in the time it takes to run. I agree. However, I'm more concerned about readability and understandability for developers less familiar with the quirks of old shells. >>> POSIX does require the three argument 'test' look for the middle argument >>> being an operator - but there might be historic shells that don't so that. >>> OTOH you are probably looking for code from the early 1980s! >>> But the POSIX spec (last time I read it) does point out the problems >>> with arbitrary strings being treated as operators causing complex expressions >>> be mis-parsed - which a leading x fixes. >> >> Good point. I just reread it and can confirm that the current version >> still notes issues mitigated by the X prefix with "historical shells" >> and with greater than 4 argument cases: >> https://pubs.opengroup.org/onlinepubs/9799919799/utilities/test.html > > The fact that the 'greater than 4 argument case' can still require > a prefix character might be considered enough to make adding one all the > time 'good practise' even though it (probably) isn't actually needed. That seems reasonable to me, although I'd prefer omitting x and prohibiting >3 argument cases, which appears to be the route shellcheck takes with SC2268 + SC2166. > While I wouldn't error not having a prefix, generating an error when > there is one seems wrong. > What does shellcheck do with [ "$a" = "$b" -o "$c" = "$d" ] ? It only produces SC2166 (discouraging -o). However, for [ "x$a" = "x$b" -o "x$c" = "x$d" ] it also produces SC2268. > Or even [ "$a" "$b" "$c" "$d" "$e" "$f "$g" ] ?? This, and [ "$a" "$b" "$c" ] and [ "$a" "$b" ] produce parser error SC1073. Unfortunately, this appears to be a long-standing shellcheck issue: https://github.com/koalaman/shellcheck/issues/1645 >> I find && and || more readable, but I'm open to changing it if you >> feel strongly. > > They get parsed entirely differently and are likely to be measurably slower. > Just FYI I tend not to use 'if' statements at all, just (eg): > [ a = b ] && echo a == b > >> Do I understand correctly that you are in favor of using the x prefix? >> I have a slight preference for leaving it off, but I'm open to adding >> it if you (or others) feel strongly. > > I wouldn't take them out and consider shellcheck wrong, but the suffix > were just stupid. Are you opposed to the patch I posted removing the suffixes? I had tagged you as Suggested-by due to misreading your first post. If the change is not something you'd suggest, I can repost without it. Thanks, Kevin