Shulou(Shulou.com)06/01 Report--

To register a process, you must first create a process.

How to create a process, you can use spawn, spawn_link, although they can create a process, but there are subtle differences:

1) create a parallel process in the current process. When the generated process crashes, the current process will not notice.

Pid = spawn (Fun).

2) if the process created by the current process crashes abnormally, the current process will disappear.

Pid = spawn_link (Fun).

There are four built-in functions in Erlang to manage the registration process, register, unregister, whereis, and registered, which are used as follows:

1) register (AnAtom, Pid): register a process Pid to an atom named AnAtom. If the atomic AnAtom is already used by another registration process, the registration will fail.

2) unregister (AnAtom): removes all registration information for processes corresponding to AnAtom. If a registration dies, it will also be automatically cancelled.

3) whereis (AnAtom)-> Pid | undefined: determine whether AnAtom has been registered by another process. If successful, the process identifier Pid is returned. If AnAtom does not have a corresponding process, atomic undefined is returned.

4) registered ()-> [AnAtom:: atom ()]: returns a list of all registered names in the system.

The atom mentioned here is different from the atom in java (I remember that there is also an atomic definition in java, which is related to thread safety), it is a kind of identification.

Example:

-module (chat).

-export ([start/0,stop/0])

Start ()->

Spawn (fun ()->

Register (chat_process,self ())

Process_flag (trap_exit,true)

Port = open_port ({spawn, ". / chat"}, [{packet,2}])

Loop (Port)

End).

Stop ()->

Chat_process! Stop.

Loop (Port)->

Receive

{call,Caller,Msg}->

Port! {self (), {command,Msg}}

Receive

{Port, {data,Data}}->

Caller! {chat_process,Data}

End

Loop (Port)

Stop->

Port! {self (), close}

Receive

{Port,closed}->

Exit (normal)

End

{'EXIT',Port,Reason}->

Exit ({port_terminated,Reason})

End.

Among them, chat_process, call, data, port_terminated and so on are an atom.

When this registration process is not needed, you can: unregister (chat_process).

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