twiddle.c

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

void
twiddle(void)
{
        static int state;
        static char states[] = { '|', '/', '-', '\\' };

        state++;
        state = state % 4;
        printf("%c\b", states[state]);
        fflush(stdout);
}

int
main(void)
{
        while(1) {
                sleep(1);
                twiddle();
        }
}