Progress – A Tool to Monitor Progress for Commands in Linux (2016)(tecmint.com)

  #!/bin/sh
  
  for pid in $@; do
  	cd /proc/"$pid"/fd || continue
  	
  	for fd in *; do
  		file=$(readlink "$fd");
  		if [ ! -z "$file" ]; then
  			size=$( (du -b "$file" 2>/dev/null || echo 0) | awk '{print $1}')
  			if [ "$size" = "0" ]; then
  				continue
  			fi
  			
  			pos=$(< ../fdinfo/"$fd" grep -F 'pos:' | grep -oP '\d+')
  			
  			percent=$(echo "100*${pos}/${size}" | bc -l | xargs printf "%2.2f")
  			echo "${file}: ${percent}% (${pos}/${size})"
  		fi
  	done
  done

           -d PID[:FD], --watchfd PID[:FD]
              Instead of transferring data, watch file descriptor FD  of  process  PID,
              and  show  its progress.  The pv process will exit when FD either changes
              to a different file, changes read/write mode, or is  closed;  other  data
              transfer  modifiers  -  and  remote  control  - may not be used with this
              option.

              If only a PID is specified, then that process will be  watched,  and  all
              regular  files  and  block devices it opens will be shown with a progress
              bar.  The pv process will exit when process PID exits.