Determine the wireless network name from command-line in Linux
Running iwgetid you get the wireless device and the SSID of the connected network. It's part of the wireless-tools - that you appear to have already installed because iwevent is also part of it.
iwlist scan should certainly work to give you the ssid. However from your example I don't see any actual wireless interfaces. I suggest pasting the output of iwconfig and ifconfig into your question to help figure that out.
Also from looking at the iwevent man page, I think perhaps your best bet is to run a loop that calls iwevent instead. When the ssid changes, iwevent will detect and report the new ssid.
Note that polling every 5 seconds sounds pretty intensive, perhaps you should run it less frequently?
I have an old script that handles a check like this using iwconfig that's worked for several years now across several Fedora distributions:
iwconfig wlan0 | grep ESSID | awk -F: '{print $2}'
Then I just make a decision in the script based on what that returns, like start up a home service or a work service. Does your iwconfig command not return info like that once associated with an access point?
using iw
Assuming that your interface is wlp3s0, you can get the SSID with iw and grep:
iw wlp3s0 info | grep -Po '(?<=ssid ).*'
The flags -P and -o are explained in this answer.