Function: ps-print-buffer

Generate and print a PostScript image of the buffer.

Interactively, when you use a prefix argument (C-u), the command prompts the
user for a file name, and saves the PostScript image in that file instead of
sending it to the printer.

Noninteractively, the argument FILENAME is treated as follows: if it is nil,
send the image to the printer. If FILENAME is a string, save the PostScript
image in a file with that name. (fn &optional FILENAME)