In an SFTP session is it possible to copy one remote file to another location on same remote SFTP server?

Question

Let say I have a file /home/user/dir1/file.txt on a remote SFTP server. I want to copy this file to lets say /home/user/dir2/file.txt, while I am i

Answer 1

Not sure what you mean by the "command". Are you referring to an SFTP protocol request? Or a command of some scriptable/command-line SFTP client (e.g. the OpenSSH sftp)?

The SFTP protocol on its own does not allow duplication of a remote file. Though there's an optional extension of the protocol named copy-file that serves the purpose.

Quoting the copy-file extension specification:

6. Copying Remote Files

byte   SSH_FXP_EXTENDED
uint32 request-id
string "copy-file"
string source-file
string destination-file
bool   overwrite-destination

This request copies a file from one location to another on the server. The server responds with SSH_FXP_STATUS.

Not many SFTP servers support the extension though. I know that ProFTPD/mod_sftp and Bitvise WinSSHD do. Notably, the OpenSSH does not (neither the server, nor the sftp client).