Shell Programming and Scripting

     proxy ftp-command
           Executes an FTP command on a secondary control connec-
           tion.  This  command allows simultaneous connection to
           two remote FTP servers for transferring files  between
           the  two servers. The first proxy command should be an
           open, to establish the secondary  control  connection.
           Enter  the  command  proxy ? to see other FTP commands
           executable on the secondary connection.

( cat <<-EOF
        open ${FirstHop}
        user ${USRfirsthop} ${PASSWDfirsthop}
        proxy open ${SecondHop}
        proxy user ${USRsecondhop} ${PASSWDsecondhop}
        put File2firsthop
        proxy put File2firsthop
        EOF
) | ftp -n -d -v

A-->B-->C

ftp serverB
user  blahblah
password  blahblah
proxy open serverB

ftp serverB
user  blahblah
password  blahblah
proxy open serverC