change_port

ECO command. Change an output port's driver, or add gate after input port 
Usage1: change_port($port, $gate, $instance, $connections);
$port: The port under ECO, can be input port or output port
$gate: New leaf gate to drive the port if the port is output
       Or add the gate after input port
$instance: The instance name for the new leaf cell, optional, the tool assigns one if it's empty
$connections: The new gate input pins connections. If it is empty, the gate is inserted in the net
   Supported formats, 1. Very detail  ".A(net0),.B(net1),.C(net2)"
                      2. Connect to the pins in alphabetical sequence 
                          "net1,net0,net2" indicating A->net1,B->net0,C->net2
                      3. Other instance/pin "U408/Y,U409/Y,net2" indicating A->U408/Y,B->U409/Y,C->net2
                      4. Special character '-' is used to connect up the original connection
Usage2: change_port($port, $inst_pin);
$port: The port under ECO, output port
$inst_pin: In the format of 'u1234/Y', instance-name/pin-name
Note: The difference of change_net and change_port command
      change_net changes all drains of the net.
      change_port changes only the port driver.

Examples:

#1. Add buffer to output port 'out1'
change_port("out1", "BUFX1", "eco_buf0", "-");