SIGKILL won't work to stop child process after child signals completion

Question

My program creates n child processes, every child count(+5) if it surpasses 100 it sends a signal to the parent, the parent should kill this child. I did the program but it won't work, it keeps counting in the first child, which means the SIGKILL didn't work.

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


pid_t pids[10];
int pidval[10];
int l;

void handler1(int mysignal)
{
    int i;
    for (i=0; i<l; i++) {
        if (pidval[i]>100) {
            kill(pids[i], SIGKILL);
            printf("\n killed ");
        }
    }
}

int main(int argc, char ** argv)
{

    int i, s;
    l = atoi(argv[1]);
    pid_t pid;
    for(i=0; i<l; i++)
    {
        pid=fork();

        if(pid<0) 
            printf("\n error \n");
        if (pid==0) {
            pids[i] = getpid();
            while(1) {
                s+=5; 
                if(s>100) 
                {
                    pidval[i]=s;
                    printf("\noverflow,%d,%d,%d",s,pids[i],getpid());
                    kill(getppid(), SIGALRM);
                };
            }
        }
        if(pid>0) {
            signa(SIGALRM,handler1);
            waitpid(-1,NULL,0);
        }
    }
}

Forked processes do not share the same variables! The child gets a _copy_ of the parent's stack/global space, however any changes made to them are not seen by the other process(es). If you want to share your data properly, you need to explicitly do so. — mah, Jan 20 '14 at 12:36
so i can make a file txt shared by all process in place of array ? — Malek Djelassi, Jan 20 '14 at 12:42

score 1 · Answer 1 · answered Jan 20 '14 at 12:37

1

Use SIGTERM, take a look at this article.

answered Jan 20 '14 at 12:37

Perefexexos

252
1
8

score 0 · Answer 2 · answered Jan 20 '14 at 13:07

I made it thanks for your advices

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




void handler1(int mysignal)
{   
FILE *pids = NULL;
FILE *pidvals=NULL;
int pid1,pid2,val,sum;
    pids=fopen("pids.txt","r");


    while(fscanf(pids,"pid = %d\n",&pid1)!=EOF)
    {   pidvals=fopen("vals.txt","r");
        while((fscanf(pidvals,"pid = %d val = %d\n",&pid2,&val)!=EOF))
        {
            if(pid1==pid2)
            sum+=val;
        }
        fclose(pidvals);
            if(sum>100) kill(pid1,SIGTERM);

    }
    fclose(pids);

}   



int main(int argc, char ** argv)
{   FILE *pids = NULL;
FILE *pidvals=NULL;

    int i, s;
    int l=atoi(argv[1]);
    pid_t pid;

    for(i=0;i<l;i++)
    {
      pid=fork();

      if(pid<0) printf("\n error \n");
      if (pid==0) {pids=fopen("pids.txt","a");
               fprintf(pids,"pid = %d\n",getpid());
               fclose(pids);
           s=0;
                   while(1){

                s+=5;
                pids=fopen("vals.txt","a");
                fprintf(pids,"pid = %d val = %d\n",getpid(),s);
                fclose(pids); 
                           if(s>100) 
                              {
                               printf(" \nsend signal\n");
                               kill(getppid(),SIGALRM);};
                               }
                  }
      if(pid>0) {
                  signal(SIGALRM,handler1);waitpid(-1,NULL,0);
                }
  }



}

SIGKILL won't work to stop child process after child signals completion

2 Answers2