On 9 February 2016, LCD 47 <[email protected]> wrote:
[...]
> Starting a (presumably long-lived) server from Vim on the other hand
> is a very different animal. A server might print things like error
> messages before it goes to background. After that it isn't supposed
> to print anything or need output from stdin (doing that would rise a
s/output/input/
> signal). A server in background is supposed to communicate with other
> processes only though a socket (INET, or UNIX domain).
[...]
> A further difference between long-lived and short-lived processes
> is the way process groups are handled. For short-lived processes, the
> sequence should be something like this:
>
> - fork()
> - in the child: exec()
Better: close stdin, then exec(). Dealing with stdin while we're
also reading output can run into a deadlock.
> - in the parent: install a SIGCHLD and waitpid()
>
> For daemons the sequence should be:
>
> - fork()
> - in the child: setsid(), fork() again, and exit
Better yet: initialize, print errors etc., then setsid(), fork()
again, and exit.
> - in the second child: exec()
Better: close fds 0-2, exec()
> - in the parent: blocking waitpid().
>
> To kill the group of a daemon, you need to kill() the negated PID
> of the _first_ child, because that's the session leader.
[...]
"Mixed" modes are possible too, but we really don't want to go
there.
/lcd
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