tail -f /var/log/escenic/engine1-catalina.out > /tmp/threaddumps.log & for i in $(seq 1 10); do kill -QUIT `cat /var/run/escenic/engine1.pid`; sleep 1; done fg

1. Starts logging Tomcat output to /tmp/threaddumps.log.
2. Triggers 10 JVM thread dumps, spaced 1 second apart.
3. Brings the logging process back to the foreground so you can stop it.

tail -f /var/log/escenic/engine1-catalina.out > /tmp/threaddumps.log &

• tail -f continuously follows (-f) a log file, here:
  /var/log/escenic/engine1-catalina.out (Tomcat’s output log for Escenic Engine 1).
• > /tmp/threaddumps.log redirects the live output into another file (/tmp/threaddumps.log).
• The trailing & sends that process to background, so it continues running while the shell remains usable.

Starts watching the log and recording everything into /tmp/threaddumps.log in the background.

for i in $(seq 1 10); do kill -QUIT \cat /var/run/escenic/engine1.pid`; sleep 1; done`

This is a loop that runs 10 times. Let’s unpack it:

• seq 1 10 → generates numbers 1 through 10.
• cat /var/run/escenic/engine1.pid → reads the PID (process ID) of the running Escenic Engine.
• kill -QUIT <pid> → sends the QUIT signal (SIGQUIT) to that Java process.
  In Java, this tells the JVM to write a full thread dump to the standard output (i.e., catalina.out).
• sleep 1 → waits one second between each signal.

It sends 10 SIGQUIT signals (one per second) → 10 thread dumps will be written into the catalina log file, which is being captured by the first command.

fg

• Brings the background process (tail -f) back to the foreground.
• This allows you to stop it later manually with Ctrl+C once you’re done collecting dumps

You can now watch the output live and stop it when you have enough thread dump data.

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