cp — Output Formats

The cp command separates data, status, and progress across output streams.

Standard Output (stdout)

send subcommand

Prints the transfer topic to stdout so it can be captured or piped to the receiver:

a3f2b1...  (64-char hex topic key)

recv subcommand (streaming mode)

When destination is -, file data is written directly to stdout:

peeroxide cp recv <topic> - > received_file.bin

Standard Error (stderr)

All status messages, progress, and connection info go to stderr, keeping stdout clean for data.

Sender output:

CP SEND example.bin (1.2 MB)
topic: a3f2b1...
connected from @deadbeef...
done: 1.2 MB in 2.3s (540 KB/s)

Receiver output:

CP RECV topic: a3f2b1...
looking up sender...
connected to @deadbeef...
Incoming file: example.bin (1.2 MB)
Save to: ./example.bin
done: 1.2 MB in 2.3s (540 KB/s)

Progress Display

When transfer size is known, cp displays a progress bar on stderr showing percentage, bytes transferred, speed, and ETA. When size is unknown (stdin source), a spinner with running byte count is shown instead.

Reliability

cp does not implement retransmission or resumption at the application layer. Reliability is provided by the UDX transport layer (BBR congestion control, retransmission, ordering). If a transfer fails mid-stream:

• The temporary file is left in place (not renamed to final destination).
• Re-running cp recv with the same topic will restart the transfer from the beginning.
• The sender must still be running and on the same topic.

For large files over unreliable networks, consider compressing the payload before transfer to reduce exposure to interruptions.