Re: How to tell if someone is connected via vnc

Hi,

1. "How can I determine what the user responds, is there errorlevels or anything like that?"

You can check for the exit status of the xmessage command

2. "What is the reason for doing ' > /dev/null 2>&1'"

It redirects any standard out and standard error to oblivion

Let's say you have a vnc session on port 5902. You want a script that checks if there's a session and display a message to the user. And you want to know if the user read the message. Here's what you could do. (you'll have to adapt and add a loop in there if you have several vnc sessions)

Edit the linux user's ~/.vnc/xstartup and add an "xhost +" in it. Otherwise you will not be able to display the message.

Use a script similar to this one: (of course, you will adapt and enhance)

#!/usr/bin/env bash

netstat -tape | grep ESTABLISHED | grep Xvnc | awk '{print $4}' | awk -F ":" '{print $2}' > log-ports

for user in `cat log-ports`
do
        case $user in
                5902)
                        export DISPLAY=:2.0; xmessage -buttons "I understand":10 -center -timeout 60 -file testmsg > /dev/null 2>&1
                        [ $? -eq 10 ] \
                            && echo "$user acknowledged!" \
                            || echo "No answer from $user!"
                        ;;
        esac

done

The user connected to 5902 will get a windowed message with a "I understand" button. If he clicks on it, you'll know. If he doesn't, it'll time out after 60 seconds and return an exit status of 0 (zero): you'll know too .

Hope it helps,
Olivier