int hr;
int min;
int sec;

char s [90];

// -----------------------------------------------------------------------------
void
getHrMinSec (
    const char *time )
{
    sscanf (time, "%d:%d:%d", &hr, &min, &sec);

    sprintf (s, " hr %d, min %2d, sec %2d", hr, min, sec);
    Serial.println (s);
}

void
loop (void)
{
    if (Serial.available ())  {
        char buf [0];
        int n = Serial.readBytesUntil ('\n', buf, sizeof(buf)-1);
        buf [n] = '\0';         // terminate with nul
        getHrMinSec (buf);
    }
}

void
setup (void)
{
    Serial.begin (9600);
    getHrMinSec ("10:15:32");
}