By the way there is a tool called "progress" which will scan all running processes of (supported) tools like gzip, cat, grep etc., and report progress of their

By the way there is a tool called "progress" which will scan all running processes of (supported) tools like gzip, cat, grep etc., and report progress of their file operations. If you want to emulate this by hand, first get the fd number of the file of interest by `ls -l /proc/PID/fd/` and then `cat /proc/PID/fdinfo/NUMBER`. There is a line called "pos", which is the position in the file.