Display progress reading/writing a file according to position information on the file descriptor.

progress.sh

#!/bin/bash

# Usage: progress.sh $(pgrep myprocess) $FD_NUMBER
# Find $FD_NUMBER by doing: ls -l /proc/$(pgrep myprocess)/fd/

fd=/proc/$1/fd/$2
fdinfo=/proc/$1/fdinfo/$2
name=$(readlink $fd)
size=$(wc -c $fd | awk '{print $1}')
while [ -e $fd ]; do
  progress=$(cat $fdinfo | grep ^pos | awk '{print $2}')
  echo $((100*$progress / $size))
  sleep 1
done | dialog --gauge "Progress reading $name" 7 100