Which is the best way to bring a file from a remote host to local host over an SSH session?

Question

When connecting to remote hosts via ssh, I frequently want to bring a file on that system to the local system for viewing or processing. Is there a way to copy the file over without (a) opening a new terminal/pausing the ssh session (b) authenticating again to either the local or remote hosts which works (c) even when one or both of the hosts is behind a NAT router?

The goal is to take advantage of as much of the current state as possible: that there is a connection between the two machines, that I'm authenticated on both, that I'm in the working directory of the file---so I don't have to open another terminal and copy and paste the remote host and path in, which is what I do now. The best solution also wouldn't require any setup before the session began, but if the setup was a one-time or able to be automated, than that's perfectly acceptable.

Answer 1

zssh (a ZMODEM wrapper over openssh) does exactly what you want.

• Install zssh and use it instead of openssh (which I assume that you normally use)

• You'll have to have the lrzsz package installed on both systems.

Then, to transfer a file zyxel.png from remote to local host:

antti@local:~$ zssh remote
Press ^@ (C-Space) to enter file transfer mode, then ? for help
...
antti@remote:~$ sz zyxel.png
**B00000000000000
^@
zssh > rz
Receiving: zyxel.png
Bytes received:  104036/ 104036   BPS:16059729

Transfer complete
antti@remote:~$ 

Uploading goes similarly, except that you just switch rz(1) and sz(1).

Putty users can try Le Putty, which has similar functionality.

Answer 2

On a linux box I use the ssh-agent and sshfs. You need to setup the sshd to accept connections with key pairs. Then you use ssh-add to add you key to the ssh-agent so you don't have type your password everytime. Be sure to use -t seconds, so the key doesn't stay loaded forever.
ssh-add -t 3600 /home/user/.ssh/ssh_dsa

After that,
sshfs hostname:/ /PathToMountTo/
will mount the server file system on your machine so you have access to it.

Personally, I wrote a small bash script that add my key and mount the servers I use the most, so when I start to work I just have to launch the script and type my passphrase.