GNU bug report logs -
#21702
shell-quote-argument semantics and safety
Previous Next
Full log
View this message in rfc822 format
Eli Zaretskii <eliz <at> gnu.org> writes:
>> From: taylanbayirli <at> gmail.com (Taylan Ulrich Bayırlı/Kammer)
>> Cc: 21702 <at> debbugs.gnu.org
>> Date: Mon, 19 Oct 2015 11:22:16 +0200
>>
>> > Like I said, this convention should be adopted project-wide. Doing so
>> > only in a few doc strings, let alone one, will only confuse, because
>> > the user will not know whether the lack of such documentation means
>> > the API is safe or unsafe.
>>
>> Yes, it should be done for every function for which the concerns I've
>> explained apply. So let's start from this one.
>
> Before we start, we need a _decision_ to do that everywhere. Then we
> could start doing that piecemeal. Before the decision is made,
> there's no reason to make any such changes.
Given all the reasons I listed, I would expect that decision to be
obvious.
>> >> I would propose something along the lines of:
>> >>
>> >> It is guaranteed that ARGUMENT will be parsed as a single token by
>> >> shells X, Y, and Z, as long as it is separated from other text via a
>> >> delimiter in the syntax of the respective shell.
>> >
>> > I don't think we want to mention specific shells explicitly, because
>> > maintaining such a list would be a burden. The standard shell of each
>> > OS is well defined and known to the users of the respective systems.
>> > Moreover, Emacs by default uses that shell automatically.
>>
>> For instance: POSIX sh, MS-DOS, and Windows NT, is not a long list.
>
> This list doesn't name shells on DOS and Windows (there are several
> good candidates). As for Posix, is it only sh? What about Bash? what
> about zsh?
>
> You see, the moment you come up with a list such as above, people will
> start complaining that their favorite shell is not in the list, and
> the list will grow. Then we will discover that some shells are not
> really compatible after all, etc. etc. It's a maintenance burden we
> had better avoided.
>
> Saying "the standard shell" avoids all that nicely, because it refers
> to a single well-known shell.
Dash, Bash and (AFAIK all versions of) ksh are POSIX sh compliant. Zsh
not unless when requested IIRC; in any case "POSIX sh" is well-defined.
My latest patch says "standard shells of MS-DOS and Windows NT." Feel
free to improve that if necessary.
>> I don't understand what "a shell command doesn't need to be quoted to be
>> harmful" is supposed to mean
>
> Something like this:
>
> rm -rf /*
What are you trying to say? Of course an arbitrary shell command can do
anything. The whole point of shell-quote-argument is to prevent a
string which is meant purely as an argument to a command to become
equivalent in power to an arbitrary shell command.
>> Here's a patch doing an improvement to the documentation like the one I
>> proposed. Of course, if you have verified that shells other than POSIX
>> sh are fully safe, feel free to improve the docstring accordingly.
>
> Thanks. However, like I said, I don't think this change would be
> correct, or needed.
I've explained the need for the change, and it is correct.
I don't understand why you're trying to make everything so difficult.
If for reasons unclear to me you absolutely refuse to accept these
improvements to shell-quote-argument's documentation, I will just
continue not using the function, because it cannot be trusted.
Taylan
This bug report was last modified 9 years and 211 days ago.
Previous Next
GNU bug tracking system
Copyright (C) 1999 Darren O. Benham,
1997,2003 nCipher Corporation Ltd,
1994-97 Ian Jackson.