('connected=$(ping -c1 8.8.8.8 2> /dev/null | grep '1 received
if [ "$connected" ]; then
...
fi
If ping does not receive any reply packets at all it will exit with code
1. If a packet count and deadline are both specified, and fewer than count
packets are received by the time the deadline has arrived, it will also
exit with code 1. On other error it exits with code 2. Otherwise it exits
with code 0. This makes it possible to use the exit code to see if a host
is alive or not.
This program is intended for use in network testing, measurement and man‐
agement. Because of the load it can impose on the network, it is unwise
to use ping during normal operations or from automated scripts.unwise یعنی «غیر عاقلانه»