[Python-Dev] subprocess not escaping "^" on Windows

[Guido van Rossum]

I assume you're talking about list2cmdline()? That seems to be used to
construct a string that can be passed to `cmd /c "{}"` -- it gets
substituted instead of the {}, i.e. surrounded by ". I honestly can't say I
follow that code completely, but I see that it escapes double quotes. Why
is there a need to escape other characters? Is there a definitive list of
special characters somewhere?

On Sun, Jan 7, 2018 at 8:17 AM, Christian Tismer <tismer at stackless.com>
wrote:

> Hi Guys,
>
> yes I know there was a lengthy thread on python-dev in 2014
> called "subprocess shell=True on Windows doesn't escape ^ character".
>
> But in the end, I still don't understand why subprocess does
> escape the double quote when shell=True but not other special
> characters like "^"?
>
> Yes I know that certain characters are escaped under certain
> Windows versions and others are not. And it is not trivial to make
> that work correctly in all cases. But I think if we support
> some escaping at all, then we should also support all special
> cases. Or what sense should an escape make if it works sometimes
> and sometimes not?
>
> The user would have to know which cases work and which not. But
> I thought we want to remove exactly that burden from him?
>
> -----
>
> As a side note: In most cases where shell=True is found, people
> seem to need evaluation of the PATH variable. To my understanding,
>
> >>> from subprocess import call
> >>> call(("ls",))
>
> works in Linux, but (with dir) not in Windows. But that is misleading
> because "dir" is a builtin command but "ls" is not. The same holds for
> "del" (Windows) and "rm" (Linux).
>
> So I thought that using shell=True was a good Thing on windows,
> but actually it is the start of all evil.
> Using regular commands like "git" works fine on Windows and Linux
> without the shell=True parameter.
>
> Perhaps it would be a good thing to emulate the builtin programs
> in python by some shell=True replacement (emulate_shell=True?)
> to match the normal user expectations without using the shell?
>
> Cheers - Chris
>
> --
> Christian Tismer-Sperling    :^)   tismer at stackless.com
> Software Consulting          :     http://www.stackless.com/
> Karl-Liebknecht-Str. 121     :     https://github.com/PySide
> 14482 Potsdam                :     GPG key -> 0xFB7BEE0E
> phone +49 173 24 18 776  fax +49 (30) 700143-0023
>
>
> _______________________________________________
> Python-Dev mailing list
> Python-Dev at python.org
> https://mail.python.org/mailman/listinfo/python-dev
> Unsubscribe: https://mail.python.org/mailman/options/python-dev/
> guido%40python.org
>
>


-- 
--Guido van Rossum (python.org/~guido)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-dev/attachments/20180107/88cebb60/attachment.html>