Continuously calls process.kill with the specified pid and a signal of 0 to test the existance of a process with the corresponding pid. Repeats with a default delay of 1500 ms.
const watch = require(`watch-pid`)
watch(42, pid => {
console.log(`Process with pid: ${pid} exited`)
})pid - process identifier
callback - called with the pid when the process no longer exists.
delay - delay between tests.