Script to monitor the usage of CPU, memory by a process via `top`

monitor-usage.sh

#!/bin/sh
##
## BEWARE: Check with your impl. of top what exactly it returns, it migth differ from mine
##
# Usage: ./monitor-usage.sh <PID of the process>
# Output: top.dat with lines such as `1539689171 305m 2.0`, i.e. unix time - memory with m suffix - CPU load in %
# To plot the output, see https://gist.github.com/holyjak/1b58dedae3207b4a56c9abcde5f3fdb5
export PID=$1
rm top.dat
while true; do top -p $PID -bn 1 -em | egrep '^ *[0-9]+' | awk -v now=$(date +%s.%N) '{print now,$6,$9}' >> top.dat; done
# top: -p <pid> target process, -b batch mode, -n 1 run once; -em display mem in MB
# egrep extracts the line starting with the pid, with the metrics
# awk prepends a date and extracts columns 6 (RES = residential memory, ie RAM) and 9, which should be the memory and cpu load

thanks!