Get zombie exec status.

main.c

#include <stdlib.h>
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

// SIGCHLD handler
void bury_zombies(int sig_number)
{
  pid_t zombie_pid;
  int stat_loc;

  if (sig_number == SIGCHLD) {
    printf("SIGCHLD handler\n");
    // More then one SIGCHLD signal can be sent from multiple zombie processes,
    // but we get only one signal. So, wait() for all finished child processes.
    while ((zombie_pid = wait(&stat_loc)) > 0)
      // Use WEXITSTATUS() macro to get exit status.
      printf("Wait() for zombie with pid %d, its exec code %d.\n", zombie_pid, WEXITSTATUS(stat_loc));
  }
}

int main()
{
  int i;
  struct sigaction sa;

  // Set up the signal handler.
  sa.sa_handler = bury_zombies;
  if (sigaction(SIGCHLD, &sa, 0)) {
    perror ("sigaction() error");
    return EXIT_FAILURE;
  }

  // Spawn 10 childs that return "i".
  int res;
  for (i = 0; i < 10; ++i) {
    res = fork();
    if (res == 0) {
      // inside the child
      printf("Child pid is %d\n", getpid());
      return i;
    } else if (res < 0 ) {
      perror("fork() error");
      return EXIT_FAILURE;
    }
  }
  printf("Parent pid is %d\n", getpid());

  getchar();
  return EXIT_SUCCESS;
}