kill() function not working in C language - c

Question

I have the following code. It generates n child and then a random number between 0 and n. So that random number lets suppose is "i". The child number i must kill his brothers.
The problem is that the kill function is not killing anything since both ptree after and before are exactly the same.
I cant found a solution, the output must be the father and the i child only since all his brothers were killed by him.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>
#include <time.h>
#include <unistd.h>
#include <math.h>
char archSalidaAntes[] = "aprocesosAntes.txt";
char archSalidaDespues[] = "aprocesosDespues.txt";
void imprimirArreglo(int arr[], int n){
int i;
for(i=0; i<n; i++){
printf("%d\t", arr[i]);
}
printf("\n");
}
void imprimirArbolTxt(char nombreArchivo[], pid_t id){
char buff[255];
sprintf(buff, "pstree -p -c -l %d > %s", (int)id, nombreArchivo);
system(buff);
}
void communicateSon(int arrProc[], int n, int fd[]){
int i;
int data;
int writeResp;
close(fd[0]); //closing input
for(i=0; i<n; i++){
data = arrProc[i];
writeResp = write(fd[1], &data, sizeof(data));
if(!writeResp){
printf("error writing");
}
}
close(fd[1]); //closing output
}
void killOthers(int n, int fd[], int randInt){
int i;
int readResp;
int killResp;
int data;
int arrProc[n];
close(fd[1]); //closing output
i = 0;
while(1){
readResp = read(fd[0], &data, sizeof(data));
fflush(stdout);
fflush(stdin);
if(!readResp){
break;
}
arrProc[i] = data;
i++;
}
imprimirArreglo(arrProc, n);
printf("id elegido: %d\n", getpid());
for(i=0; i<n; i++){
if(i!= randInt){
printf("killing: %d\n", arrProc[i]);
killResp = kill((pid_t)arrProc[i], SIGKILL);
if(killResp < 0){
printf("error kill: %d \n", killResp);
}
int aux = kill(arrProc[i], 0);
printf("aux: %d\n", aux);
}
}
close(fd[0]); //closing input
char com[30];
sprintf(com, "pstree -p %d", getppid());
system(com);
}
int main(int argc, char **argv){
int n;
int i;
int *arrProc;
int randInt;
int fd[2];
pid_t pId;
n = atoi(argv[1]);
printf("n = %d\n", n);
srand(time(NULL));
arrProc = (int*) malloc(sizeof(int) * n);
randInt = rand() % n;
pipe(fd);
for(i=0; i<n; i++){
pId = fork();
if(pId){
arrProc[i] = (int)pId;
if(i == (n-1)){
char com[30];
sprintf(com, "pstree -p %d", getppid());
system(com);
communicateSon(arrProc, n, fd);
waitpid(arrProc[randInt], NULL, 0);
printf("termino la espera del hijo\n");
free(arrProc);
}
} else if(pId == 0){ //hijos
if(i==randInt){
killOthers(n, fd, randInt);
exit(0);
} else{
break;
}
}
}
sleep(0.5);
return 0;
}

Answer 1

Since main process never calls waitpid for other children all of them become zombies after getting killed.
Update: you should also close pipe ends descriptors in other child processes prior to putting them to sleep, otherwise killer child process will get stuck at waiting for more data to come from the pipe.
} else{
close(fd[0]);
close(fd[1]);
break;
}
Update: sleep takes unsigned int number of seconds, so sleep(0.5) will be equivalent to sleep(0).

Answer 2

Try with sleep(1).
The sleep() function wants an integer argument, so sleep(0.5) equals to zero - which is probably not "long enough" for your demo to work. The child processes may terminate before the kill signal can reach them.