Shellscript to monitor a log file if keyword triggers then execute a command?

Question

Is there a cheap way to monitor a log file like tail -f log.txt, then if something like [error] appears, execute a command?

Thank you.

Answer 1

I also found that you can use awk to monitor for pattern and perform some action when pattern is found:

tail -fn0 logfile | awk '/pattern/ { print | "command" }'

This will execute command when pattern is found in the log. Command can be any unix command including shell scripts or anything else.