Rather than using the standard UNIX function printf for routine text output, a module which is similar in appearance is provided, which allows for installing arbitrary printing output functions. This can be used, for instance, to mirror output to a log file for instance, or to send text to an X window. The primary change is to use a function called print with exactly the same arguments as for the standard printf function.
public void print( char format, ... )
public void set_print_function(
void (*function) ( char  ) )
public void push_print_function()
public void pop_print_function()