#define _GNU_SOURCE

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


int main(int argc, char * argv[]){
	int targetpid;
	int targetgid;
	char* procplace;
	struct stat st;
	if (argc != 2){
		fprintf(stderr, "error - require exactly 1 argument\n");
		return 1;
	}
	if (sscanf(argv[1], "%i", &targetpid) != 1) {
		fprintf(stderr, "error - argv[1] not an integer\n");
		return 2;
	}
	
	if (group_member(getegid()) == 0) {
		fprintf(stderr, "error - User is not part of the egid group %d\n", getegid());
		return 3;
	}
	// todo check if pid exists

	procplace = (char*) malloc(16*sizeof(char));
	
	sprintf(procplace, "/proc/%d", targetpid);
	stat(procplace, &st);
	targetgid = st.st_gid;
	free(procplace);
	
	printf("pid: %d gid: %d\n", targetpid, targetgid);
	procplace = NULL;

	if (targetgid != getegid()){
		fprintf(stderr, "error - target gid is not equal to our egid. %d != %d\n", targetgid, getegid());	
		return 4;
	}
	printf("Killing %d\n", targetpid);
	kill(targetpid, SIGTERM);
}