Get progress of tar extract for use in other commands

extract.sh

#!/bin/sh

tar_path="file.tar.xz"
output_dir="output"

# Use pipe viewer to show progress of extraction
pv --quiet "${tar_path}" | \
  tar --extract --xz --directory "${output_dir}" &
 
# Store ID of the pv process
pv_pid=$(pgrep -ox "pv")

# Print update every second
pv --numeric --interval 1.0 --watchfd $pv_pid:3 2>&1 | \
while read prog; do
  echo "Installing root filesystem: ${prog}%"
done