[Python-Dev] Pondering some changes to python.c... (original) (raw)

Sean Reifschneider jafo@tummy.com
Mon, 8 Apr 2002 15:05:23 -0600

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

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.

Sean

The important thing is not to stop questioning. Curiosity has its own reason for existing. -- Albert Einstein Sean Reifschneider, Inimitably Superfluous <jafo@tummy.com> tummy.com - Linux Consulting since 1995. Qmail, KRUD, Firewalls, Python