internet connection tester script

[kellyremo]

http://pastebin.com/raw.php?i=rykHdvBh

bix.hu and www.yahoo.com are "pingable" test sites.
127.0.0.1 could not be pinged [firewall drops all icmp]

i have a "oneliner" that echoes if theres "internet connection or no".
$ ping -W 1 -c 2 bix.hu >& /dev/null && ping -W 1 -c 2 www.yahoo.com >& /dev/null && echo "internet connection ok" || echo "no internet connection"
internet connection ok
$ ping -W 1 -c 2 127.0.0.1 >& /dev/null && ping -W 1 -c 2 www.yahoo.com >& /dev/null && echo "internet connection ok" || echo "no internet connection"
no internet connection
$ ping -W 1 -c 2 127.0.0.1 >& /dev/null && ping -W 1 -c 2 127.0.0.1 >& /dev/null && echo "internet connection ok" || echo "no internet connection"
no internet connection
$ ping -W 1 -c 2 bix.hu >& /dev/null && ping -W 1 -c 2 127.0.0.1 >& /dev/null && echo "internet connection ok" || echo "no internet connection"
no internet connection
$ ping -W 1 -c 2 bix.hu >& /dev/null && ping -W 1 -c 2 www.yahoo.com >& /dev/null && echo "internet connection ok" || echo "no internet connection"
internet connection ok
$

Ok!

But: if i want the "oneliner" to only go along when theres internet connection:
$ while $TORF; do ping -W 1 -c 1 bix.hu >& /dev/null && ping -W 1 -c 1 www.yahoo.com >& /dev/null && TORF=false || TORF=true; done
$ while $TORF; do ping -W 1 -c 1 127.0.0.1 >& /dev/null && ping -W 1 -c 1 www.yahoo.com >& /dev/null && TORF=false || TORF=true; done
$ while $TORF; do ping -W 1 -c 1 127.0.0.1 >& /dev/null && ping -W 1 -c 1 127.0.0.1 >& /dev/null && TORF=false || TORF=true; done
$ while $TORF; do ping -W 1 -c 1 bix.hu >& /dev/null && ping -W 1 -c 1 127.0.0.1 >& /dev/null && TORF=false || TORF=true; done
$ while $TORF; do ping -W 1 -c 1 bix.hu >& /dev/null && ping -W 1 -c 1 www.yahoo.com >& /dev/null && TORF=false || TORF=true; done
$

It just doesn't work.

Goal: if theres no internet connection, then the oneliner must loop until there is internet connection. if theres internet connection the oneliner ends.

what am i missing?

[Bryn M. Reeves]

On 01/28/2011 11:28 AM, kellyremo wrote:
> http://pastebin.com/raw.php?i=rykHdvBh
>
> bix.hu and www.yahoo.com are "pingable" test sites.
> 127.0.0.1 could not be pinged [firewall drops all icmp]
>
> i have a "oneliner" that echoes if theres "internet connection or no".
> $ ping -W 1 -c 2 bix.hu >& /dev/null && ping -W 1 -c 2 www.yahoo.com >& 
> /dev/null && echo "internet connection ok" || echo "no internet connection"
> internet connection ok
> $ ping -W 1 -c 2 127.0.0.1 >& /dev/null && ping -W 1 -c 2 www.yahoo.com >& 
> /dev/null && echo "internet connection ok" || echo "no internet connection"
> no internet connection
> $ ping -W 1 -c 2 127.0.0.1 >& /dev/null && ping -W 1 -c 2 127.0.0.1 >& /dev/null 
> && echo "internet connection ok" || echo "no internet connection"
> no internet connection
> $ ping -W 1 -c 2 bix.hu >& /dev/null && ping -W 1 -c 2 127.0.0.1 >& /dev/null && 
> echo "internet connection ok" || echo "no internet connection"
> no internet connection
> $ ping -W 1 -c 2 bix.hu >& /dev/null && ping -W 1 -c 2 www.yahoo.com >& 
> /dev/null && echo "internet connection ok" || echo "no internet connection"
> internet connection ok
> $
>
> Ok!
>
> But: if i want the "oneliner" to only go along when theres internet connection:
> $ while $TORF; do ping -W 1 -c 1 bix.hu >& /dev/null && ping -W 1 -c 1 
> www.yahoo.com >& /dev/null && TORF=false || TORF=true; done
> $ while $TORF; do ping -W 1 -c 1 127.0.0.1 >& /dev/null && ping -W 1 -c 1 
> www.yahoo.com >& /dev/null && TORF=false || TORF=true; done
> $ while $TORF; do ping -W 1 -c 1 127.0.0.1 >& /dev/null && ping -W 1 -c 1 
> 127.0.0.1 >& /dev/null && TORF=false || TORF=true; done
> $ while $TORF; do ping -W 1 -c 1 bix.hu >& /dev/null && ping -W 1 -c 1 127.0.0.1
> > & /dev/null && TORF=false || TORF=true; done
>
> $ while $TORF; do ping -W 1 -c 1 bix.hu >& /dev/null && ping -W 1 -c 1 
> www.yahoo.com >& /dev/null && TORF=false || TORF=true; done
> $
>
> It just doesn't work.
>
> Goal: if theres no internet connection, then the oneliner must loop until there 
> is internet connection. if theres internet connection the oneliner ends.
>
> what am i missing?

Instead of using a variable (that has funky scoping in shell) just make the &&
compound command the loop condition and place it in a subshell:

while (! ping -W 1 -c 1 bix.hu && ! ping -W 1 -c 1 www.yahoo.com )&>/dev/null;
do /bin/true ; done

Or you can write the same as:

while (! (ping -W 1 -c 1 bix.hu && ping -W 1 -c 1 www.yahoo.com))&>/dev/null; do
/bin/true ; done

It's probably not the best way to do it though - this little shell loop eats up
fair bit of CPU time.

Just putting a "sleep 1" instead of /bin/true makes the load barely noticable
but if you're on a system that's using Network Manager then you could also look
at the information provided by the nmcli tool to see if it would meet your
requirements.

Regards,
Bryn.

[JB]

kellyremo <kellyremo <at> zoho.com> writes:
> ... 
> Goal: if theres no internet connection, then the oneliner must loop until
> there is internet connection. if theres internet connection the oneliner
> ends.what am i missing?
> ...

Test:

1. there is internet connection to both

$ TORF=true; while $TORF; do ping -W 1 -c 1 bix.hu >& /dev/null && ping -W 1
-c 1 www.yahoo.com >& /dev/null && TORF=false || TORF=true; echo $TORF; sleep 1;
done
false
$

2. there is no internet connection to at least one

$ TORF=true; while $TORF; do ping -W 1 -c 1 www.blakstar.org >& /dev/null &&
ping -W 1 -c 1 www.yahoo.com >& /dev/null && TORF=false || TORF=true; echo
$TORF; sleep 1; done
true
true
true
true
^C
$

Nota bene !
Let's assume negation is represented by "~" sign.
~(a && b) equivalent to ~a || ~b
~(a || b) equivalent to ~a && ~b

JB