Output the memory usage of a pid and measure the change.

watch-mem-usage

#!/usr/bin/env bash
## Output the memory usage of a pid and measure the change.

set -euo pipefail

pid=$1

last_usage_mb=0
while true; do
    mem_usage=$(ps -p "$pid" -o size=)
    
    usage_mb=$(bc <<< "scale = 2; $mem_usage / 1024")
    change_mb=$(bc <<< "scale = 2; $usage_mb - $last_usage_mb")
    if [[ $(bc <<< "$change_mb > 0") == 1 ]]; then
        change_mb="+$change_mb"
    fi

    last_usage_mb="$usage_mb"

    if [[ $usage_mb != 0 ]]; then
        echo -ne "\r                                                  \r"
        echo -n "Mem: $usage_mb MiB ($change_mb MiB/s)"
    fi
    sleep 1
done