blink.c

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

int main(int argc, char** argv) {
  int state = 0;
  while (1) {
    char *cursor = state ? "█" : " ";
    printf("\r%s", cursor);
    fflush(stdout);
    state = ~state;
    sleep(1);
  }
  return 0;
}