Perlpv is a proof-of-concept pipe viewer similar to Andrew Wood's pv—but written in perl, for eventual use
internally in syncoid.
You might be surprised just how finicky it is both getting extremely performant file reads and positioning the cursor for dynamic display updates in Perl. I wouldn't, because... well, because I've learned otherwise. With any luck, this working proof of concept will save you the hours of headaches I went through getting it working!
To use the program as-is, the syntax is simple:
you@box:~$ /path/to/perlpv sourcefile targetfile
and you'll get a dynamic, interactive display that updates itself once per second while the transfer progresses, like so:
jim@elden:~$ sudo ./perlpv /dev/nvme0n1 /dev/null
Transferred 7.6GiB of 1.8TiB (at average rate 4.9GiB/sec), estimated completion in 00:06:21
^C
jim@elden:~$
The averate rate (and estimated completion) are derived by keeping separate running averages for transfer rates for the last five minutes, last one minute, and the last ten seconds. These three averages plus the transfer rate for the last block copied are then averaged together to estimate the time to completion.
