Change the behaviour depending on whether you are in local network or not

Question

I am making bash script like this

if [ "if I am in local "]; then
  ssh myuser@192.168.11
else
  ssh myuser@myserver.com
fi

How could I get if I am in local or not?

Answer 1

One possibility is to test whether 192.168.11 is ping-able:

if ping -qc1 192.168.11 >/dev/null; then
  ssh myuser@192.168.11
else
  ssh myuser@myserver.com
fi

If ping receives a response from 192.168.11, then it exits with return code 0 (success) and the then clause is executed. If no responses are returned, the else clause is executed.

The option -c1 tells ping to only send one packet. If your local network is unreliable (unlikely), you may need to send more than one packet.

The -q option tells ping to be a bit more quiet but that doesn't really matter because we dump its output into /dev/null.

Note that IP addresses are typically written with 4 values, not 3: a number may be missing from 192.168.11.

Documentation

From man ping:

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.

Answer 2

This works with assumption then IP addresses starting with 10,127,197,172 are reserved IP for private network.

myIp=$(hostname -I) # or i based on your version. 
echo $myIp |grep -q -P '(^127\.)|(^10\.)|(^172\.1[6-9]\.)|(^172\.2[0-9]\.)|(^172\.3[0-1]\.)|(^192\.168\.)'

if [ "$?" -eq 0 ];then
  echo "Private Network"
else
  echo "Over Internet"
fi

Inspiration from Here .