I have a long running build process that I want to terminate after a certain log output is given.

What i normally do is just watch the process running and when the log entry appears I control-c. Is there a better way to do this, im a Windows guy so dont know where to start.

The command I am running is npx nx run myapp:ios and the log line is Project successfully prepared (ios)

As per Josh Friedlander's comment I have tried the following command and variations but cannot get it to work, the process continues beyond the log line defined:

npm run mybuildscript | while read -r LOGLINE; do echo ${LOGLINE}; [[ "${LOGLINE}" == "Project successfully prepared (ios)" ]] && pkill -P $$ npm; done