char *replace(const char *src, const char *from, const char *to)
{
   size_t size    = strlen(src) + 1;
   size_t fromlen = strlen(from);
   size_t tolen   = strlen(to);
   char *value = malloc(size);
   char *dst = value;
   if ( value != NULL )
   {
      for ( ;; )
      {
         const char *match = strstr(src, from);
         if ( match != NULL )
         {
            size_t count = match - src;
            char *temp;
            size += tolen - fromlen;
            temp = realloc(value, size);
            if ( temp == NULL )
            {
               free(value);
               return NULL;
            }
            dst = temp + (dst - value);
            value = temp;
            memmove(dst, src, count);
            src += count;
            dst += count;
            memmove(dst, to, tolen);
            src += fromlen;
            dst += tolen;
         }
         else /* No match found. */
         {
            strcpy(dst, src);
            break;
         }
      }
   }
   return value;
}