GNU Emacs Lisp Reference Manual

16.6: Variables Affecting Output

Variable: standard-output

The value of this variable is the default output stream---the stream that print functions use when the stream argument is nil.

Variable: print-escape-newlines

If this variable is non-nil, then newline characters in strings are printed as \n and formfeeds are printed as \f. Normally these characters are printed as actual newlines and formfeeds.

This variable affects the print functions prin1 and print, as well as everything that uses them. It does not affect princ. Here is an example using prin1:

(prin1 "a\nb")
     -| "a
     -| b"
     => "a
b"
(let ((print-escape-newlines t))
  (prin1 "a\nb"))
     -| "a\nb"
     => "a
b"

In the second expression, the local binding of print-escape-newlines is in effect during the call to prin1, but not during the printing of the result.

Variable: print-length

The value of this variable is the maximum number of elements of a list that will be printed. If a list being printed has more than this many elements, it is abbreviated with an ellipsis.

If the value is nil (the default), then there is no limit.

(setq print-length 2)
     => 2
(print '(1 2 3 4 5))
     -| (1 2 ...)
     => (1 2 ...)

Variable: print-level

The value of this variable is the maximum depth of nesting of parentheses and brackets when printed. Any list or vector at a depth exceeding this limit is abbreviated with an ellipsis. A value of nil (which is the default) means no limit.

This variable exists in version 19 and later versions.