getgroups

#include < sys/types.h >
#include < unistd.h >
#include < grp.h >

#include 

int main(){
    gid_t list[3];
    
    list[0] = 3000;
    list[1] = 3001;
    list[2] = 3002;
    if (setgroups(3, list) < 0){
        perror("setgroups");
        return 1;
    }
    return 0;
}