Correct api for stopping a process cleanly or killing it?

[Chris Maughan]

If I have a process that I suspect has already exited, but want to kill it if not, is this the right sequence?
i.e. Is the noop the 'exit' if already exited part? Followed by terminate and kill?

reproc::stop_actions stop = {
            { reproc::stop::noop, reproc::milliseconds(0) },
            { reproc::stop::terminate, reproc::milliseconds(TerminateProcessMilliseconds) },
            { reproc::stop::kill, reproc::milliseconds(KillProcessMilliseconds) }
        };
proc->stop(stop);

It wasn't clear to me from the examples the correct approach here.
The scenario is a process that has been running for a while, but has been asked to exit by another mechanism (it has received a network message, for example). So I 'hope' that it has already gone, but if not, I wish to close it.

[Daan De Meyer]

Replace the noop with reproc::stop::wait. Waiting 0 milliseconds is equivalent to just checking if the process is still running.

[Chris Maughan]

Thanks for the quick response ;) So what does the noop mean?

[Daan De Meyer]

To do absolutely nothing at all. stop_actions is a struct with three members but it's not required to supply three actions. Sometimes a single action is sufficient so we need an action to indicate that nothing should happen which is noop. Usually you don't specify it explicitly as noop is the default action.

For example:

  reproc::stop_actions stop = {
    { reproc::stop::terminate, reproc::milliseconds(5000) },
    { reproc::stop::kill, reproc::milliseconds(2000) },
    {}
  };

The last action is not necessary so we just default initialize it which corresponds to the noop action as it is the first member of the stop enum.

[Chris Maughan]

OK, that's great, and makes perfect sense. Thanks.

[Daan De Meyer]

I enabled Github Discussions for reproc, please post any further questions on using reproc there

[Chris Maughan]

Will do, thanks for the help :)