// gcc -o cache_clear cache_clear.c; chmod u+s cache_clear

#include <stdio.h>
#include <unistd.h>

int main(int argc, char** argv) {
  FILE  *f;
  printf("uid=%d\n", geteuid());

  if((f = fopen("/proc/sys/vm/drop_caches","w")) == NULL) printf("Cannot open input file:  /proc/sys/vm/drop_caches \n");
  printf("sync \n");
  system("sync");
  printf("echo 1 > /proc/sys/vm/drop_caches \n");
  fprintf(f,"1\n");
  return 0;
}