vprintf, vfprintf, and vsprintf

#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 );

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 (Other Standard C Functions) va_arg().

For example:

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 );
}