[Tutor] checking return status of 'ping' in windows

[Hugo Arts]

On Sat, Jan 21, 2012 at 7:47 PM, Nikunj Badjatya
<nikunjbadjatya at gmail.com> wrote:
> Hi All,
>
> I am using the following snippet to check the availability of an IP address.
> If that IP addr is found free than it can be used later on for further
> operations.
> Python ver 3.2
> Windows OS
>
> {{{
> pingret = subprocess.Popen('ping {0}'.format(IPaddr),
> shell=True,universal_newlines=True, \
>                     stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
> status = pingret.wait()
> if status == 0:
>     print("WARN  The IP given in the input is not free")
> .....
> .....
> }}}
>
> Normal ping operation on windows cmd prompt can give 3 outputs.
> 1) "destination host unreachable
> 2) "request timed out"
> 3) "Reply from 192.168.1.1: bytes=32 time=3ms TTL=64"
>
> Now,
> I was expecting the "status" in above snippet to hold '0' only in case of
> no. 3)
> But even when we have case 1), 'status' is holding '0'.
> i.e. The exit status of ping is 0, even when destination host is
> unreachable.!
>

This appears to be windows specific. Linux ping will return an exit
code of 1 if either zero responses are received or a packetcount and
deadline are specified and not met. I'm not sure why it doesn't work
that way on windows, but testing a bit for myself it seems to be the
platform's fault and not python's, since calling EXIT 1 will correctly
return a status code of 1.

> How do I make my snippet to work as desired. i.e even if destination host is
> unreachable, 'status' should hold '1'  and hold '0' only when it gets reply
> from that ip address.??
>

rather than using the wait() call, use Popen.communicate() which
returns the output of the program, and check that directly for your
three cases.

HTH,
Hugo