Commands
There are three system message commands, each with the same subcommands.welcome- Dispatched whenever a user joins the server.goodbye- Dispatched whenever a user leaves the server.boost- Dispatched whenever a user boosts the server.
The 
boost event is only dispatched if the server has the Discord System
Message enabled or whenever the user receives the Server Booster role
which only occurs once.
The following examples use the
welcome command, but the same syntax is
applied for the other system message commands.Creating a system message
You can create a system message with thewelcome add command.
The
--self_destruct flag in system messages schedules the message for
deletion after a specified time, which must be between 6 and 60 seconds.
Removing a system message
You can remove a system message with thewelcome remove command.

Related commands
Viewing a system message
Viewing a system message
You can use the
welcome view command to view a system message.Viewing all system messages
Viewing all system messages
You can use the
welcome list command to view all system messages.