Debugging automatic quotation in subprocess.Popen()

[Eryk Sun]

On 10/7/22, c.buhtz at posteo.jp <c.buhtz at posteo.jp> wrote:
>
> I need to improve my understanding about how subprocess.Popen() does
> quote arguments. I have special case here.
>
> Simple example:
> Popen(['ls', '-l']) results on a shell in "ls -l" without quotation.

The shell is only used if Popen is instantiated with `shell=True`. The
above example does not use the shell. It runs the "ls" executable
directly. On POSIX systems, fork() and exec() are called to create the
child process. The argument list is passed to exec() and becomes the
argv array of the application's main() entry point function.

On Windows systems, CreateProcessW() is called to created the child
process. It requires a command-line string instead of an argument
array. The argument list gets joined into a command-line string via
subprocess.list2cmdline(), which is based on the rules that are used
by the Windows C runtime library when it parses a command line into
the argv array of an application's [w]main() entry point. That said, a
Windows application is free to parse its command line however it
wants, so listcmdline() is little more than a best guess. On Windows,
Popen() may have to be called directly with a command-line string in
some cases.