you can give it a pid too -d PID[:FD], --watchfd PID[:FD] Instead of transferring data, watch file descriptor FD of process PID,

you can give it a pid too -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.