Multi-process problem

howlhowl

The parent process creates a child process. If the parent process ends, how does the child process know that the parent process has ended?
If the parent process gets up again, how to receive the information of the original child process.
No socket programming method

无间风雪

This has something to do with priority. . .
    The communication between the child process and the parent process needs to detect the mutual status. .