r utilities
R-Utilities belong to the Berkeley services of TCP/ IP and are used for faster communication between Unix workstations. They are comparable in function to file transfer or telnet.
The r-commands support among other things the copying offiles, the remote copy( rcp), the command input by remote shell ( rsh), the command execution by remote execute ( rexec), the logging into a computer with remote login( rlogin) and the recognition of users with remote who ( rwho) or of Unix stations in the network (ruptime).
Since the security of the r commands is not guaranteed, the r tools should only be used in systems that have no security requirements and whose users trust each other.