Re: SCP Recursive Flag

[Bob Proulx]

Colton Peltier wrote:
> While working with some coworkers recently we noticed a strange
> inconsistency between cp and scp, that caused us some confusion. For
> the cp tool a -r or -R will do a recursive copy of directories, but
> for scp only -r will. The -R flag for scp is gives illegal
> option. What is the reasoning behind this?

You are comparing 'cp' and 'scp' but those are apples and oranges.
The 'scp' command is designed to be compatible with the 'rcp' command.
The rcp command is one of the BSD 'r'commands.  The rcp command uses
the -r option.  That is why scp uses it.

  http://www.freebsd.org/cgi/man.cgi?query=rcp&manpath=2.10+BSD

While rcp is insecure it was one of the standard ways to do a remote
file copy between systems.  The scp command is designed to be
compatible with it and to replace it.

Therefore you should not be comparing scp and cp.  Those commands are
unrelated.  The cp command came from AT&T Unix.  The scp command came
from rcp.  The rcp command came from BSD.

A yet newer command for remote file copy is 'rsync'.  It is the newest
addition from the brilliance of Tridgell.  Again the options are
unrelated to cp or rcp/scp.

The rcp command is insecure and should never be used where security is
a concern.  The scp command is secure but is an old command that is
burdened by needing to remain backward compatible with the rcp
command.  I recommend that you use the rsync command in preference
over the scp command.

All of the commands 'cp', 'rcp'/'scp', and 'rsync' are uniquely
written individual commands from different origins.  None of them
should be compared with the other!

Feel free to argue that being a "melting pot" where many different
commands from all over are all ported to the same system and used
intermingled together is a bad thing but for me it is one of the
strong points of the system.

Note that the scp command is not part of GNU coreutils.  This group
can't do anything about it.  If you want changes in it you would need
to take them up with the OpenSSH folks.  But I expect they will try to
avoid feature creep and suggest that it remain as a compatibility
command for rcp since rsync is already available.

Bob