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.
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
