openssh unix dev - Jan 2005 - Feature requests for scp and ssh

Hi

Would it be possible to add an option to the scp command, so that if a
destination file already exists, rather than overwriting it, scp just
skips the destination file, prints a message to stderr and returns an
error (non-zero) exit? That would help me immensely.

Also, you might want to think about providing a way to execute a
series of ssh, scp and sftp commands through one authentication
session, so if using password authentication you don't need to keep on
re-keying the password. Maybe have some kind of background daemon,
which holds the session open once authenticated, and then the
ssh/scp/sftp clients connect to it to perform operations. (I know key
authentication would work here, but sometimes server admins aren't so
keen on key authentication, and would prefer you physically entering
your password.)

Cheers
Simon Kissane

Simon Kissane wrote:
> Would it be possible to add an option to the scp command, so that if a
> destination file already exists, rather than overwriting it, scp just
> skips the destination file, prints a message to stderr and returns an
> error (non-zero) exit? That would help me immensely.
That would require another option to be passed to the remote scp process 
to enable that behaviour, which would be a potential interop problem. 
This means it's not likely to ever happen (see 
http://www.openssh.com/faq.html#2.10).

You can use sftp in batch mode to do it with something like:
$ echo "ls /tmp/foo" | sftp -b - localhost || \
	echo "put foo /tmp/foo" | sftp -b - localhost

This isn't going to save you from partial transfers, however.  You may 
be better off using rsync-over-ssh.
> Also, you might want to think about providing a way to execute a
> series of ssh, scp and sftp commands through one authentication
> session, so if using password authentication you don't need to keep on
> re-keying the password.
That already exists.  Check out the ControlPath and ControlMaster 
options in 3.9x.

-- 
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
     Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

Simon Kissane wrote:
> Would it be possible to add an option to the scp command, so that if a
> destination file already exists, rather than overwriting it, scp just
> skips the destination file, prints a message to stderr and returns an
> error (non-zero) exit? That would help me immensely.
I suggest you use 'rsync' over 'ssh'.  The rsync program has a
many
options.  Look at the -u, --update option.

  http://rsync.samba.org

Bob