I answered you on Reddit as well, but this is easier.

The way I'd do it is to check the output of the ifconfig command for the existance of a tun or tap interface. Most likely, one of those will be created when you connect to the VPN.

#!/usr/bin/env bash

if ifconfig -s | grep -qE "(tun|tap)[0-9]+"; then

    # Run popcorn time

else

    zenity --error --text "VPN is not running."

fi

ifconfig is used to configure network interfaces. If you don't supply any arguments, it will return all the available network interfaces along with a bunch of information about them. The -s flag makes it only output a small list of the interfaces. My ifconfig -s when connected to a VPN looks like this:

➜  ~  ifconfig -s

Iface   MTU Met   RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg

eth0       1500 0   5302413      0      0 0       1971869      0      0      0 BMRU

lo        65536 0    323789      0      0 0        323789      0      0      0 LRU

tun0       1500 0         0      0      0 0            15      0      0      0 MOPRU

As you can see, on the last line there's an interface called "tun0", which is the interface that my VPN connection uses. Since it's there, I know that I'm connected to my VPN. If you want to learn more about ifconfig, see man ifconfig.

The | (pipe) character "pipes" (sends) the output of the first command into the second command - grep.

The grep command searches through input text for anything that matches a pattern. The -E flag tells it that the pattern is an "extended regex". What that is is a bit too much to explain, but if you're curious, you can read man grep. The pattern I've supplied, (tun|tap)[0-9]+ will search for a string that starts with "tun" or "tap", followed by at least one digit. The -q flag tells grep that I don't want it to output the actual text that it found, I'm just interested to know whether it found something or not.

By putting that in the if statement, the condition will be true if grep finds a matching string, so the code within the then clause will be run. If it fails to find a matching string, the code in the else clause will run.

Lines starting with # are comments - code that is ignored and not run. Since I don't know where Popcorn Time is installed, I don't know how to run it, so you'll have to fill that in yourself.

The first line, starting with #! is called the "shebang". That line simply tells your shell (the thing that you use to run the script with) what program it should use to execute the script. In this case, we probably want it to use bash.

Someone in the comments suggested that you look at the output of the route command, which could be good, but when I tried it it was pretty slow. If you had multiple VPN connections and you wanted to check that a specific one was up, then the route command would be much better (because you could look up a specific IP address), but for the simple use-case, I don't think it's necessary.