Re: what causes SIGTERMs?

["Matthew Studley" <matthew.studley@uwe.ac.uk>]

Hi all

thanks for the help regarding linux signals... very useful!

I have written this little test program, which I then send a SIGTERM using
another process.
(I've been testing this under the current stable release of Debian)

I notice that, while siginfo_t.si_signo seems to have a meaningful value,
all other fields e.g. si_pid are ZERO !

Does anybody have any ideas about this?

cheers Matt

============================================


#include <signal.h>
#include <stdio.h>

/*- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
void myHandler(int i, siginfo_t *info, void *v){
  printf("i = %d\n", i);
  printf("signo is %d\n", info->si_signo);
  printf("calling pid is %d\n", info->si_pid);
  printf("calling uid is %d\n", info->si_uid);
  printf("errno : %d\n", info->si_errno);
  printf("code : %d\n", info->si_code);
  fflush(stdout);
}
/*- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
int main(void){
  int i;
  struct sigaction mySigaction;

  mySigaction.sa_sigaction = (myHandler);
  sigemptyset (&mySigaction.sa_mask);
  mySigaction.sa_flags = SA_SIGINFO;      //SA_RESTART | SA_SIGINFO;
  if(sigaction(SIGTERM, &mySigaction, NULL) < 0) {
  perror("ERROR: registering Handler Function\n");
  exit(1);
  }

  while(1){
    // do nothing.
  }
}
/*- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

========
>
> Matthew Studley wrote:
>
> > I wonder whether you could help me?  I have a problem; I'm running an
> > application I've written in C under Slackware 7.1  Occasionally it
receives
> > a SIGTERM.
> >
> > * In what circumstances do processes get sent a SIGTERM?
>
> If something raises it with kill(). Note that SIGTERM is the default
> signal sent by the kill and killall commands.
>
> > * Am I correct that this is unlikely to be issued in response to a bug
in my
> > code?
>
> Correct. SIGTERM isn't sent synchronously (i.e. in response to the
> actions of the process which receives it).
>
> > * How can I find which process is issuing the SIGTERM against my code?
>
> Install a signal handler using sigaction() with the SA_SIGINFO flag;
> the sending process ID will be in the si_pid field of the siginfo_t
> structure. Other fields of that structure may also contain useful
> information.
>
> --
> Glynn Clements <glynn.clements@virgin.net>
>
>