pv · Knowledge Base

1 October 20262 min read

pv (Pipe Viewer) monitors the progress of data flowing through a pipeline. Insert it anywhere between two processes and it shows elapsed time, throughput, bytes transferred, a progress bar and an ETA — on stderr, so the data passes through untouched.

Usage

Use it like cat to get a progress bar on a file (size is known, so you get a percentage and ETA):

shell

pv big.iso > /dev/sdX

pv backup.tar.gz | tar xzf -

Drop it into the middle of a pipeline:

shell

tar cf - dir/ | pv | zstd > dir.tar.zst

When reading from a pipe, the total size is unknown — pass it with -s to get a real percentage:

shell

tar cf - dir/ | pv -s $(du -sb dir/ | cut -f1) | gzip > dir.tar.gz

Watch compressed vs. uncompressed rates side by side with named, stacked bars (-c uses cursor positioning so multiple instances don't clobber each other):

shell

pv -cN raw big.log | gzip | pv -cN gz > big.log.gz

Rate-limit a transfer (e.g. to not saturate a link):

shell

pv -L 2m file | ssh host 'cat > file'

Count lines instead of bytes:

shell

some-generator | pv -l > out.txt

Attach to an already-running process and watch its open file descriptors (Linux):

shell

pv -d $(pidof cp)

Options

Option	Description
`-p, --progress`	Show progress bar
`-t, --timer`	Show elapsed time
`-e, --eta`	Show estimated time remaining
`-r, --rate`	Show current transfer rate
`-a, --average-rate`	Show average transfer rate
`-b, --bytes`	Show total bytes transferred
`-n, --numeric`	Print integer percentages, one per line (for piping into e.g. `dialog --gauge`)
`-q, --quiet`	No output (useful with `-L` for pure rate limiting)
`-s, --size SIZE`	Assume total size is `SIZE` (accepts suffixes like `1g`)
`-l, --line-mode`	Count lines instead of bytes
`-N, --name NAME`	Prefix output with a name
`-c, --cursor`	Use cursor positioning escapes (for multiple `pv`s in one pipeline)
`-L, --rate-limit R`	Limit transfer to `R` bytes per second
`-B, --buffer-size`	Use a transfer buffer of the given size
`-d, --watchfd PID`	Watch file descriptors of process `PID` instead of transferring data
`-R, --remote PID`	Change the options of an already-running `pv` (e.g. raise its rate limit on the fly)