Run bash command from awk system only once

Question

I am using tail -F to monitor a severe weather alert server log file and awk to filter and execute a command if the conditions for an alert are met. I need to execute the bash command(an ssh command sent to a Pi to trigger an alert LED) in system only once, not one time for every match. Everything is working except the system command is running once for every line matched. Here is what I have so far:

tail -F /home/user/test.txt | stdbuf -oL awk '/ZZZ029/{getline; if (/SV.W/) print system("command")}'

Current output(number of lines could vary):

/O.NEW.KBMX.SV.W.0028.190314T2350Z-190315T0030Z/
/O.CON.KFFC.SV.W.0021.000000T0000Z-190315T0015Z/
/O.NEW.KBMX.SV.W.0028.190314T2350Z-190315T0030Z/
/O.CON.KFFC.SV.W.0021.000000T0000Z-190315T0015Z/
/O.NEW.KBMX.SV.W.0028.190314T2350Z-190315T0030Z/
/O.CON.KFFC.SV.W.0021.000000T0000Z-190315T0015Z/

Expected output:

/O.NEW.KBMX.SV.W.0028.190314T2350Z-190315T0030Z/

I need just one line of output so the system command will run only once. Or just a way to run the command once regardless of number of lines of output.

Answer 1

From current output what you provided from my understanding you want to remove duplicates

pipeline_previous_command|awk '{if(!seen[$1]++)print $1}'

/O.NEW.KBMX.SV.W.0028.190314T2350Z-190315T0030Z/
/O.CON.KFFC.SV.W.0021.000000T0000Z-190315T0015Z/

Suppose if you want ouput as output which mentioned above

raveen:~$ pipeline_previous_command |  awk '/W.0028/{if(!seen[$1]++)print $1}'

/O.NEW.KBMX.SV.W.0028.190314T2350Z-190315T0030Z/