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(elisp)Output Variables

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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' that
     print with quoting.  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-escape-nonascii
     If this variable is non-`nil', then unibyte non-ASCII characters
     in strings are unconditionally printed as backslash sequences by
     the print functions `prin1' and `print' that print with quoting.

     Those functions also use backslash sequences for unibyte non-ASCII
     characters, regardless of the value of this variable, when the
     output stream is a multibyte buffer or a marker pointing into one.

 - Variable: print-escape-multibyte
     If this variable is non-`nil', then multibyte non-ASCII characters
     in strings are unconditionally printed as backslash sequences by
     the print functions `prin1' and `print' that print with quoting.

     Those functions also use backslash sequences for multibyte
     non-ASCII characters, regardless of the value of this variable,
     when the output stream is a unibyte buffer or a marker pointing
     into one.

 - Variable: print-length
     The value of this variable is the maximum number of elements to
     print in any list, vector or bool-vector.  If an object 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.

   These variables are used for detecting and reporting circular and
shared structure--but they are only defined in Emacs 21.

 - Variable: print-circle
     If non-`nil', this variable enables detection of circular and
     shared structure in printing.

 - Variable: print-gensym
     If non-`nil', this variable enables detection of uninterned symbols
     (Note: Creating Symbols) in printing.  When this is enabled,
     uninterned symbols print with the prefix `#:', which tells the Lisp
     reader to produce an uninterned symbol.