What I wrote was a bit different than the command given in the help of URPO, but since I made a mistake, it would not have worked anyway. So it's good you didn't try . Anyway, if you just copy a file (instead of adding stuff to an existing one like the command in URPO help does), its easier to use the scp command.Is your ~/.ssh/authorized_keys really a directory instead of a file? link
cat ~/.ssh/id_urpo | ssh user@computer 'cat >> ~./ssh/authorized_keys/id_urpo'