Socket programming -- close (the difference between shutdown and close)

There are two APIs for closing a socket: Close and shutdown. What are their differences?

Close ----- In the case of multi-process, close the socket ID of this process, but the link is still open. Other processes using this socket ID can also use this link, this socket ID can be read or written until all processes are closed to close the socket, but it is completely closed when it is actually executed, neither sending nor receiving data is processed. If the peer sends data, it will receive the RST message.

Shutdown -- even in the case of multi-process, it is also directly closed. If the socket link is broken, the link of other processes will be closed, but it is only closed when it is closed, that is, the data transmission channel is closed, and data receiving is acceptable. If it is written, it may receive a sigpipe signal, which may not be received until the socket buffer is filled.