David Riley <fraveyd...@gmail.com> wrote:
> On Oct 23, 2011, at 10:44 PM, aaabb...@hotmail.com wrote:
>
> > exp:
> > os.system('ls -al'）
> > #I like to catch return value after this command. 0 or 1,2,3....
> > does python support to get "$?"?
> > then I can use something like:
> > If $?==0:
> > ........
> > ................
>
> From the manual (http://docs.python.org/library/os.html#os.system):
>
> "On Unix, the return value is the exit status of the process encoded in the
> format specified for wait(). Note that POSIX does not specify the meaning of
> the return value of the C system() function, so the return value of the
> Python function is system-dependent."
>
> From the linked wait() documentation, the data returned is in a 16-bit
> integer, with the high byte indicating the exit status (the low byte is the
> signal that killed the process). So:
>
>
>
>
> status = os.system("foo")
>
> retval, sig = ((status >> 8) & 0xFF), (status & 0xFF)
>
... or
retval, sig = os.WEXITSTATUS(status), os.WTERMSIG(status)
for some insulation from low-level details.
Nick
>
>
>
> In the above example, your return status will end up in "retval".
>
> Of course, you probably ought to be using subprocess to run your subprocesses
> anyway; it's a lot more powerful and a lot harder to enable things like shell
> injection attacks. See:
> http://docs.python.org/library/subprocess.html#subprocess-replacements
> (which, of course, shows a direct replacement for os.system which is just as
> vulnerable to shell injection)
>
>
> - Dave
>
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