=====vprintf, vfprintf, and vsprintf=====
Syntax:

<code>
    #include <cstdarg>
    #include <cstdio>
    int vprintf( char *format, va_list arg_ptr );
    int vfprintf( FILE *stream, const char *format, va_list arg_ptr );
    int vsprintf( char *buffer, char *format, va_list arg_ptr );
</code>
These functions are very much like printf(), fprintf(), and sprintf(). The
difference is that the argument list is a pointer to a list of arguments.
va_list is defined in cstdarg, and is also used by [[c/other/va_arg]]. For example:

<code>
     void error( char *fmt, ... ) {
       va_list args;
       va_start( args, fmt );
       fprintf( stderr, "Error: " );
       vfprintf( stderr, fmt, args );
       fprintf( stderr, "\n" );
       va_end( args );
       exit( 1 );
     }
</code>