[UPDATE]
Here is the latest incarnation of the script. It will now automatically determine the VPN UUID for you (provided you only have one VPN setup on you're system, see lines 12 through 15 if you have more then one VPN).
Now the only thing you will need to change in this script is line 8, where you would replace "myprogram" with whatever program you want to be stopped when the VPN looses its connection.
I've also added more comments (lines preceded with a # symbol are comments) in the script to try and help explain some things as best I can given my current low skill level.
Caution: As previous poster's have pointed out, please use this script at your own discretion as I am a novice at writing scripts and do not know how to check for latencies in this script between when the VPN fails and when the program that depends on that vpn is stopped. It has been my experience that this script "appears" to stop the program instantly (via manual visual inspection) when the VPN looses its connection. However as stated I'm not sure how to test this aspect of the script using code to get an accurate measure of any latency that might be present. If any one knows how to test this please provide a comment.
To use this script:
1.) Copy the code below into a file and name it whatever you want with an extention ".sh", for example "vpnmon.sh"
2.) Open a text editor and replace the word "myprogram" on line 8 with the name of the program you wish to have stopped when the VPN fails or looses its connection.
Example: If using qbittorrent, then line 8 would look like this:
progID='qbittorrent'
3.) Save and close the file.
4.) To run it from the command line, type bash "pathtofile/filename.sh" where pahttofile is the path to your file, and filename.sh is the name of the file you gave in step 1.
Example: If you named your file vpnmon.sh and placed it in a directory called Programs which resides in your home directory then you would execute the script by the following on a command line:
bash "~/Programs/vpnmon.sh"
Script:
Code:
#!/bin/bash
# This script monitors a VPN connection and stops a program when that connection
# is lost, then restarts that program when the connecton is re-established.
#Attmept an initial connection until connected
#------------------------------------------------------------------------------
# Set progID to whatever program you need stopped when VPN fails.
progID='myprogram'
# Get the UUID of the only vpn on the system.
# Note if you have more then one VPN configured on your system, you will need to
# comment out line 14 and uncomment line 15 replacing "your-vpn-name-here" with
# the name of the vpn you want to use with this script.
uuid_str=`nmcli -t -f TYPE,UUID con list |grep vpn |sed s/vpn://g`
# `nmcli -t -f NAME,UUID con list |grep your-vpn-name-here |sed s/your-vpn-name-here://g`
function connectVPN()
{
# If the connection is just started or lost, try to reconnect then break out once connected.
while :
do
connected=`nmcli -t -f VPN con status |grep yes` #Store the current state of the VPN connection.
if [ "$connected" = "yes" ]; then
# echo "VPN connection active"
break
else
echo "Attempting VPN connection in 5 seconds."
sleep 5 #Give the VPN time to recover so we don't abuse it with reconnection requests.
nmcli -p con up uuid $uuid_str #Retry the VPN
fi
done
}
connectVPN
sleep 5 #Give the connection time to stabelize before continueing.
# Run the program and get its process ID number.
#------------------------------------------------------------------------------
# Note: Here a string can not be used to represent the program because the name
# of the string will be stored as the job name instead of the program name. So
# instead a variable is used to store the name of the program (see line 8).
$progID &
sleep 5
btID=`pgrep $progID` #changed from 'pidof' because 'pidof' quit working.
sleep 2
date
#Monitor the connection for discconnections and secure VPN dependancies.
#------------------------------------------------------------------------------
while true; do
vpnstring=$(nmcli -t -f VPN con status|grep -c yes) #Define a string to test, 0 = no connection, 1 = connected.
case $vpnstring in #Test the connection string.
"0")
date
echo "VPN disconnected. Stoping VPN dependancies"
kill -SIGSTOP $btID #Connection lost stop the VPN dependancy.
echo "VPN dependancies stopped."
jobs
connectVPN
echo "VPN dependencies restarted." #Placed here so it wont be endlessly repeated in the outer loop.
date
;;
"1")
kill -SIGCONT $btID
;;
esac
sleep 5
done
Notes:
Each section of the above code is delimited by a commented out dashed line as:
#------------------------------------------------------------------------------
There are 3 sections in the above code:
1.) The VPN is connected if it isn't connected already.
2.) The program that is dependent on the VPN's connection status is started and its process ID is captured.
3.) The VPNs connection status is monitored via a simple loop, and if it ever looses the connection, the dependent program is stopped until the connection can be re-established.
Also note there are two different types of single quotes being used in this script as stated in an earlier post.
In earlier comments it was reported that this code throws an environment variable error message. I'm not sure why that would happen. I have a default Ubuntu 12.04 system and this code works fine when I tested it in terminal. If you're testing this script and you get an error, can you please include how you were using the script and what command interpreter your terminal is using?
To find out what command interpreter you are using you could try doing the following from a command line:
ps h -p $$ -o args='' | cut -f1 -d' '
The above command was obtained from: "How to detect command interpreter from within a shell"
Here is a description of each part of the above command (there is probably a much faster / more simple to do this query but, I just grabbed one of the first google results which worked for me):
ps: gives a process list
h: do not print column headers
-p: list only the process id (PID) of each program that is running.
$$: replaced by the shell with current PID
-o args: print the command line, no other information
cut: cut the output into parts
-f1: print only the first field
-d' ': use a space as a field separator
If you get "bash" as the output of the command described above then the script in this post should work.
I'm not familiar with other command interpreters so I can't be sure as to how this script will behave when used with anything other then bash.
Launcher Icon Creation: (very step by step instructions for Gnome3).
If you are using Ubuntu with a Gnome3 desktop (or possibly any other OS with a Gnome3 desktop) here are the steps I used to create an icon to launch this script in a terminal with one click.
You should only do this step if you have determined that this script will work for you. (Check "To use this script" earlier in this post to see if it will work).
1.) I did a search for an icon for the program that depends on the VPN connection.
2.) I opened up gimp and edited this icon to look the way I wanted it to look.
3.) I saved the program someplace logical where I could find it if I thought to look for it again later.
4.) I opened up Alacarte ([sudo apt-get install alacarte] if you don't have it installed already, or [ALT+F2] then "alacarte" if you already have it installed).
5.) Select an appropriate group to place the launcher in (in my case I selected the "Internet" group (left hand panel)).
6.) Select [New Item] button (second button down from the top, on the right hand side of the window).
7.) In the window that opens there is an icon in the upper left. Clicking on this allows you to select an icon to associate with the program. Here I selected the icon that was saved in step 3 above.
8.) Type: "Application in Terminal".
9.) Name: Here I used whatever name I wanted to associate with the script. So for example if you are using a bit torrent client you could type "qbtscript" or something like this for the name here.
10.) Command: Here we enter what we used for step 4 from "To use this script" earlier in this post.
11.) Comment: This is optional and just serves as a short description of the icon.
12.) Click save and close alacarte.
13.) Open the overview screen (again this short tutorial is for Gnome3, moving the mouse to the upper left corner opens the overview screen).
14.) Type the name you gave in step 9. You should see the icon you created and saved in steps 2 and 3 of this list of steps. Click hold, drag, and drop this icon into your list of favorites (left hand side of the screen for a default Gnome3 desktop in Ubuntu 12.04) and from this point on all you need to do is click on this icon, to start the script. A terminal window will automatically open and run the script.
Thanks again for all you're comments and help in creating this script.
Adv Reply
Originally Posted by rnerwein
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