A small cli utility to allow you to watch and evaluate the output of a command and run other commands when matches are found in the output.
I created it to use with a single-process docker container so that I could watch the stdout and stderr and take action when a Tomcat web server reports that a specific warfile has been deployed. It might be useful for other jobs as well.
npm install -g outwatch
You can get access to the line that matched <matchexpr> by using the variable OUTWATCH_LINE in your output.
This watches a file, looks for the word 'error' and writes lines with that error to errorReport.txt
outwatch "tail -f /some/file.log" "/error/gi" "touch errorReport.txt; echo \$OUTWATCH_LINE >> errorReport.txt"
To see explanation of all CLI options run:
outwatch --help