scanf time demo

#include <stdio.h>   /* fscanf, fprintf */
#include <errno.h>   /* errno           */
#include <string.h>  /* strerror        */
#include <stdbool.h>

typedef struct
{
  unsigned h;
  unsigned m;
  unsigned s;
} HMS;

/* format time */
bool convert(HMS* hms)
{
  bool over24 = false;

  if (hms->s >= 60) { hms->m++;  hms->s%=60; }

  if (hms->m >= 60) { hms->h++;  hms->m%=60; }

  if (hms->h >= 24) { hms->h%=24; over24=true;   }

  return over24;
}

int main(int argc, char** argv)
{
  HMS t;
  int n = 0;
  errno = 0;

  if (argc> 1)
    {
      n = sscanf( argv[1] , "%2u:%2u:%2u", &t.h, &t.m, &t.s);
    }
  else
    {
      fprintf(stdout, "Enter the time (hh::mm:ss):\t" );

      n = fscanf( stdin, "%2u:%2u:%2u", &t.h, &t.m, &t.s);
    }


  if( n==3  &&  !errno)
    {
      if ( convert(&t) ) fprintf( stdout, "clock turned over (>24 hrs)\n\n");

      fprintf( stdout, "hours:    %d \n" , t.h);

      fprintf( stdout, "minutes:  %d \n" , t.m);

      fprintf( stdout, "seconds:  %d \n" , t.s);
    }
  else
    fprintf(stdout, "invalid format. %s\n", strerror(errno) );

  return 0;
}