Log memory usage of Java every second as it's running

java-memory-logging.sh

#!/bin/bash
#helper that gives the current unix time, in seconds
function now() {
  date -u "+%s"
}
#helper that calculates elapsed ms
START="$(now)"
function elapsed() {
  NOW="$(now)"
  echo $((NOW-START))
}
#helper that prints a single line of stats about latest java proc
function stats() {
  pid=$(pgrep java | tail -n 1)
  if [ -z "$pid" ] ; then
    echo "$(elapsed), 0, 0"
  else
    echo "$(elapsed), $pid, $(ps -o rss= -p $pid)"
  fi
}
#main loop
echo "elapsed-sec, proc-id, mem-rss-kb"
while [ 1 ] ; do
  stats
  sleep 1
done