Parent process not running when child process aborted via ctrl-\ - c

Question

I'm doing this assignment in which a number of child processes are generated and if they're aborted (ctrl-\ or ctrl-4) the parent process should run instead. This is the code:
int main(int argc, char *argv[])
{
/* The rest of the code is omitted. "times", "arg1"
and "cmd1" are parameters passed when running the program */
for(cont = 0; cont < times; cont++)
{
pid = fork();
if(pid == 0)
execvp(arg1,cmd1);
else if (pid >0) {
wait(&status);
if (WCOREDUMP(status) !=0)
printf("Core dump generado\n");
}
}
return 0;
}
The program runs a Linux command a number of times, with argv[1] being the number of times, and arg[2], argv[3] and so on the Linux command itself.
It runs fine if it's not cancelled. But when I try to abort it (for instance using a sleep command and then typing ctrl-4):
./ntimes 2 sleep 10
^\Quit (Core dumped)
it generates a dump. I want the parent process to print a message instead. I've tried with signal handling functions and many other things, but I can't seem to make it work.

Answer 1

SIGQUIT targets the whole foreground process group of your terminal—it kills the parent along with the child.
To prevent it from killing the parent, you need to either:
ignore it or block it in the parent
catch it in the parent
With approach 1., you'll need to unblock it/unignore it in the child before execing.
With approach 2., the signal disposition will be automatically defaulted upon execing so it won't affect the child, however, having at least one signal handler will open your application up to the possibility of EINTR errors on long-blocking syscalls such as wait, so you'll need to account for that.
Here's an example of approach 2. You can try it on e.g., ./a.out sleep 10 #press Ctrl+\ shortly after this.
#include <signal.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <errno.h>
void h(int Sig){}
int main(int argc, char *argv[])
{
sigaction(SIGQUIT, &(struct sigaction){.sa_handler=h}, 0);
int cont, status, times=1;
pid_t pid;
for(cont = 0; cont < times; cont++)
{
pid = fork();
if(pid == 0)
execvp(argv[1],argv+1);
else if (pid >0) {
// retry on EINTR
int rc; do{ rc=wait(&status); }while(0>rc && EINTR==errno);
if (0>rc) return perror("wait"),1;
if (WIFSIGNALED(status)){
if (WCOREDUMP(status))
printf("Core dump generado\n");
}
}
}
return 0;
}