I'm writing a bar script and I don't want to check WiFi's ssid and it's state every 20/30 seconds when I know that it won't change for a while. I would like to use something like bspc's command subscribe report which updates only if there is a change.
Here is what I have for context:
while : do case "con=$(cat /sys/class/net/w*/operstate 2>/dev/null)" in [Dd]*) ssid='No Connection' ;; [Uu]*) ssid=$(iwgetid -r) ;; esac echo "$ssid" sleep 30 done I probably did a terrible job at explaining what I want the script to actually do, so here is a better version:
I don't want to refresh the bar every 20/30 seconds just to display the same ssid every time, I only want to refresh it if there is a different output from the script.
I did find a solution by total accident:
# This function checks if the line is actually different or not, # it's stolen from herbstluftwm example script uniq_linebuffered() { awk -W interactive '$0 != l { print ; l=$0 ; fflush(); }' "$@" } while : do case "con=$(cat /sys/class/net/w*/operstate 2>/dev/null)" in [Dd]*) ssid='No Connection' ;; [Uu]*) ssid=$(iwgetid -r) ;; esac echo "$ssid" sleep 10 || break done > >(uniq_linebuffered) &