[Python-Dev] Pondering some changes to python.c...

Guido van Rossum guido@python.org
Mon, 08 Apr 2002 17:46:24 -0400

> On Mon, Apr 08, 2002 at 04:51:57PM -0400, Guido van Rossum wrote:
> >When I run a Python script that has a #! directly, ps doesn't show me
> >the "python" part -- only the script name.  This is in Linux (Red Hat
> >7.2).  Maybe it's different for you?

> I was told at one point that "#!/usr/bin/env python" was the preferred
> she-bang incantation.  However, calling it directly on my 7.2 box seems to
> show Python in either case:
>    guin:tmp$ printf '#!/usr/bin/python\nimport time; time.sleep(5)' >testscript
>    guin:tmp$ ./testscript & ps -awlx | grep testscript
>    000   500  8297  6741  10   0  2256 1192 do_sel S    pts/0      0:00 /usr/bin/python ./testscript
>    guin:tmp$ printf '#!/usr/bin/env python\nimport time; time.sleep(5)' >testscript 
>    guin:tmp$ ./testscript & ps -awlx | grep testscript
>    000   500  8300  6741   9   0  2256 1192 do_sel S    pts/0      0:00 python ./testscript

Alas, yes.  Default ps shows the script name, but ps -f does indeed
show the Python interpreter.

> >I'm not sure I understand.  If you have the argc/argv/environ set, why
> >do you need to know &argc and &argv?
> On Linux and a few other systems, setting the ps string requires re-writing
> the block of memory starting at argv[0].  If the data in envp is
> allocated next to argv, you can also make use of that (so that you can
> write strings longer than "python testscript" in length).
> The typical way of doing this involves first making a copy of argv and envp
> for the process to continue using, because otherwise argv suddenly becomes
> something entirely different than what it originally was.
> So, we need to know &argv so that we can hand back the new location.

Sigh.  The more I hear about this, the more I think, too ugly, this
doesn't belong in Python.

--Guido van Rossum (home page: http://www.python.org/~guido/)