On Fri, Feb 19, 2021 at 06:49:45AM +0100, Sebastien Marie wrote:
> On Thu, Feb 18, 2021 at 10:23:05PM -0600, Edgar Pettijohn wrote:
> > I'm having trouble using kevent(2) to catch signals. Below is a sample
> > program. It should catch SIGHUP and SIGUSR1 and just print it out.
> > Instead when i send the process sighup with `kill -SIGHUP $PID` it
> > exits and the word Hangup is writtin to the terminal. If I use
> > `kill -SIGUSR1 $PID` the process exits and the words User defined signal 1
> > are written to the terminal. What am I doing wrong?
>
> to quote kqueue(2) man page about signals:
>
> [EVFILT_SIGNAL] coexists with the signal(3) and sigaction(2)
> facilities, and has a lower precedence. The filter will record all
> attempts to deliver a signal to a process, even if the signal has
> been marked as SIG_IGN. Event notification happens after normal
> signal delivery processing.
I read this and it just didn't click.
>
> and to quote signal(3) man page about default action:
>
> Name Default Action Description
> SIGHUP terminate process terminal line hangup
> SIGUSR1 terminate process user-defined signal 1
>
> Your program needs to first ignore SIGHUP and SIGUSR1 (so the process
> will not terminate). This way, the kqueue(2) subsystem should be able
> to process them correctly.
>
> Thanks.
> --
> Sebastien Marie
With the proper signal({SIGHUP,SIGUSR1}, SIG_IGN) calls it works as expected.
Thanks,
Edgar
