SlackBuildsOrg/system/progress

This tool can be described as a Tiny, Dirty, Linux-and-OSX-Only C
command that looks for coreutils basic commands (cp, mv, dd, tar,
gzip/gunzip, cat, etc.) currently running on your system and displays
the percentage of copied data. It can also show estimated time and
throughput, and provides a "top-like" mode (monitoring).