Process argument passing problems

Brian Inglis
Fri Jun 21 21:13:00 GMT 2019

On 2019-06-21 14:15, Hans-Bernhard Bröker wrote:
> Am 21.06.2019 um 17:19 schrieb
>> I have to following problem (using cmd.exe):
>> C:\cygwin64\home\xy>C:\cygwin64\bin\echo.exe -DFOO=\"BAR\" -DBAR=\"FOO\"
>> I would have expected:
> Expecting cmd.exe to parse command lines in anything resembling a sane
> way is, unfortunately, an exercise in futility.
> Microsoft allowed blanks in filenames with hardly any regard for the
> concepts of command lines and their parsing.  We're still fighting with
> the repercussions now, 25 years later.
>> Context: I'm executing various cygwin programs through (native) Python and
>> passing C macros to gcc like 'gcc -DFOO=\"BAR\"' fails because of this.
> Are you sure Python even goes through cmd.exe to pass those command
> lines?  If it doesn't, figuring out what cmd.exe does may be even less
> fruitful than it already is.
>> More background:
> Please note that that's about MSYS2, which, while closely related to
> Cygwin, is not really the topic of this mailing list.

Not only are you running from cmd, you are running Cygwin /bin/echo, which does
additional command line parsing when not invoked from Cygwin.
Please note that the cmd escape char is "^" caret/uparrow not backslash "\" so
you might have more luck trying e.g.
	> \cygwin64\bin\echo ^"-DFOO=\"BAR\" -DBAR=\"FOO\"
	> \cygwin64\bin\echo ^"-DFOO=\^"BAR\^" -DBAR=\^"FOO\^"
depending on what you are trying to pass from where to what.

All quotes and backslashes are stripped by shells while building the calling
argv array, so you should only need a backslash or quotes to pass args with
spaces from cmd to Cygwin programs, unless programs require quotes around option
values, which gcc shouldn't.

You will have to read up on the details of MSYS2 and Python command line parsing
and how they pass command line arguments to WinExec(), ProcessCreate(), or
ShellExecute() to run programs.

Using Cygwin shells and python would make this a whole lot easier!

Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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