Please have a spinner in sleep(1)

sleep.c

/* We present: high-quality highly accurate nanosleep with a spinner.
 *
 * Compile and run:
 * 
 *     gcc -shared -fPIC -o libsleep.so sleep.c
 *     LD_PRELOAD=./libsleep.so sleep 3
 * */

#include <time.h>

const char spinner_chars[] = "|\\-/";

int nanosleep(const struct timespec *rqtp, struct timespec *rmtp) {
    struct timespec ts;
    unsigned int i;

    ts.tv_sec = 0;
    ts.tv_nsec = 100000000;  // 100 ms

    for (i = rqtp->tv_sec * 10; i > 0; i--) {
        putchar('\r');
        putchar(spinner_chars[i % 4]);
        fflush(0);
        __nanosleep(&ts, NULL);
    }

    return 0;
}