Trap signal using kill in child process?

Question

Working on Linux, I want to catch the signal I have sent using kill in the child process and then print the loop but I don't know how.

I can't seem to get my code that catches the signal.

Here is my code so far:

#include <stdio.h>
#include <signal.h>
#include <sys/types.h> 
#include <sys/ipc.h> 
#include <sys/shm.h> 

int SHMSIZE = 9;
int alarmFlag = 0;

void main()
{
 int shmid; 
 int *shm; 
 pid_t pid = fork();

 if(pid == 0) {
  pause();
  shmid = shmget(4000, SHMSIZE, 0);
  shm = shmat(shmid,0,0);

  int i;
  for(i=0;i<SHMSIZE;i++)
   printf("<%d , ",shm[i]);
 }
 else
 {
   int *n;
   shmid = shmget(4000,SHMSIZE,0666 | IPC_CREAT);
   shm = shmat(shmid,0,0);
   n = shm;  

   int i;
   for(i=0;i<SHMSIZE;i++)
    n[i] = i;

   int result = kill(pid, SIGUSR1); 
   wait(NULL);  
 }
}

Answer 1

The pause() in your program on its own doesn't catch a signal, it just sleeps until a signal is delivered, but if that signal isn't caught (using sigaction() or signal() , as Jonathan Leffler wrote), it terminates the process. So, you have to add eg signal(SIGUSR1, catch); before pause(); and

void catch(int signum) { }

before main() .