[2] According to OpenSSH developers in April 2019, SCP is outdated, inflexible and not readily fixed; they recommend the use of more modern protocols like SFTP and rsync for file transfer.
[3] As of OpenSSH version 9.0, scp client therefore uses SFTP for file transfers by default instead of the legacy SCP/RCP protocol.
A client can send (upload) files to a server, optionally including their basic attributes (permissions, timestamps).
(Remote-to-remote mode did not support opening two SCP connections and using the originating client as an intermediary).
Text transmitted due to the SSH profile (e.g. echo "Welcome" in the .bashrc file) is interpreted as an error message, and a null line (echo "") causes SCP client to deadlock waiting for the error message to complete.
Since OpenSSH 9.0, the program has been updated to use the newer, more secure SFTP protocol; an -O option is added for using SCP with old SCP-only servers.
For example, copying a file from host: As the Secure Copy Protocol implements file transfers only, GUI SCP clients are rare, as implementing it requires additional functionality (directory listing at least).