On Sun, 10 Oct 2004, Jason Lunz wrote:
The biggest problem on Windows is that not all executables use the Microsoft C runtime. Some use other C runtimes, others parse the command line directly and don't use argv at all.
So why does subprocess use cmdline2list() in the parent on unix to emulate the way a child subprocess might parse the string on windows? (But only if it's written in C, uses the MSC runtime, and uses the argv/argc handed to main() rather than calling GetCommandLine() itself). Why not emulate CommandLineToArgvW()? or something else entirely? I think it would be cleaner not to emulate anything at all.
One goal with subprocess is being able to write cross-platform applications. For example, it should be possible to open up www.python.org in Mozilla. The best way to write this is:
In this case, the list form is translated to the string form when running on Windows.
Why allow the string form on UNIX? Answer: Symmetri, plus that some users that has been using os.system() for a long time thinks it's nice to be able to do:
subprocess.call("ls -l /foo/bar")
There's a risk that UNIX users might expect UNIX shell-like quoting support rather than the MSC one, though.
The unix execv is just *different*. Both the Windows and the Unix interfaces have capabilities the other doesn't offer.
Well, the windows interface is a subset of the unix one. The length of argv on windows is limited to 1.
True, if we are talking about the UNIX exec functions. When executing through a UNIX shell, the native interface is a string.
I think Peter's approach of supporting both forms - a single string as a command line, and list of strings as an argv list, and converting both to the more natural OS-native form as needed, is sensible (I would, I argued for it when he was developing it!)
I can see that it's trying to be symmetric and orthogonal, but I don't think that the result is worth it in this case. In what scenario is the use of cmdline2list() really useful?
I don't really have a good example.
If we should remove the cmdline2list stuff, what should happen if the users passes a string on UNIX? Do you prefer:
1) Run through the shell (automatic shell=True). or 2) A ValueError raised.
I guess alternative 1 is most intuitive. That would line up with popen2 as well.
Anyone objecting to this change?
/Peter Åstrand firstname.lastname@example.org