[Emacs-diffs] Changes to os.texi

[Glenn Morris]

CVSROOT:        /sources/emacs
Module name:    emacs
Changes by:     Glenn Morris <gm>       07/09/06 04:22:35

Index: os.texi
===================================================================
RCS file: os.texi
diff -N os.texi
--- /dev/null   1 Jan 1970 00:00:00 -0000
+++ os.texi     6 Sep 2007 04:22:35 -0000       1.1
@@ -0,0 +1,2004 @@
address@hidden -*-texinfo-*-
address@hidden This is part of the GNU Emacs Lisp Reference Manual.
address@hidden Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 
2001,
address@hidden   2002, 2003, 2004, 2005, 2006, 2007  Free Software Foundation, 
Inc.
address@hidden See the file elisp.texi for copying conditions.
address@hidden ../info/os
address@hidden System Interface, Antinews, Display, Top
address@hidden Operating System Interface
+
+  This chapter is about starting and getting out of Emacs, access to
+values in the operating system environment, and terminal input, output,
+and flow control.
+
+  @xref{Building Emacs}, for related information.  See also
address@hidden, for additional operating system status information
+pertaining to the terminal and the screen.
+
address@hidden
+* Starting Up::         Customizing Emacs startup processing.
+* Getting Out::         How exiting works (permanent or temporary).
+* System Environment::  Distinguish the name and kind of system.
+* User Identification:: Finding the name and user id of the user.
+* Time of Day::                Getting the current time.
+* Time Conversion::     Converting a time from numeric form
+                          to calendrical data, and vice versa).
+* Time Parsing::        Converting a time from numeric form to text
+                          and vice versa.
+* Processor Run Time::  Getting the run time used by Emacs.
+* Time Calculations::   Adding, subtracting, comparing times, etc.
+* Timers::             Setting a timer to call a function at a certain time.
+* Idle Timers::         Setting a timer to call a function when Emacs has
+                          been idle for a certain length of time.
+* Terminal Input::      Accessing and recording terminal input.
+* Terminal Output::     Controlling and recording terminal output.
+* Sound Output::        Playing sounds on the computer's speaker.
+* X11 Keysyms::         Operating on key symbols for X Windows
+* Batch Mode::          Running Emacs without terminal interaction.
+* Session Management::  Saving and restoring state with X Session Management.
address@hidden menu
+
address@hidden Starting Up
address@hidden Starting Up Emacs
+
+  This section describes what Emacs does when it is started, and how you
+can customize these actions.
+
address@hidden
+* Startup Summary::         Sequence of actions Emacs performs at startup.
+* Init File::               Details on reading the init file (@file{.emacs}).
+* Terminal-Specific::       How the terminal-specific Lisp file is read.
+* Command-Line Arguments::  How command-line arguments are processed,
+                              and how you can customize them.
address@hidden menu
+
address@hidden Startup Summary
address@hidden Summary: Sequence of Actions at Startup
address@hidden initialization of Emacs
address@hidden startup of Emacs
address@hidden @file{startup.el}
+
+   The order of operations performed (in @file{startup.el}) by Emacs when
+it is started up is as follows:
+
address@hidden
address@hidden
+It adds subdirectories to @code{load-path}, by running the file named
address@hidden in each directory in the list.  Normally this file
+adds the directory's subdirectories to the list, and these will be
+scanned in their turn.  The files @file{subdirs.el} are normally
+generated automatically by Emacs installation.
+
address@hidden
+It sets the language environment and the terminal coding system,
+if requested by environment variables such as @code{LANG}.
+
address@hidden
+It loads the initialization library for the window system, if you are
+using a window system.  This library's name is
address@hidden/@var{windowsystem}-win.el}.
+
address@hidden
+It processes the initial options.  (Some of them are handled
+even earlier than this.)
+
address@hidden
+It initializes the window frame and faces, if appropriate.
+
address@hidden
+It runs the normal hook @code{before-init-hook}.
+
address@hidden
+It loads the library @file{site-start} (if any), unless the option
address@hidden (or @samp{--no-site-file}) was specified.  The library's file
+name is usually @file{site-start.el}.
address@hidden @file{site-start.el}
+
address@hidden
+It loads your init file (usually @file{~/.emacs}), unless the option
address@hidden (or @samp{--no-init-file}), @samp{-Q}, or @samp{--batch} was
+specified on the command line.  The @samp{-u} option can specify
+another user whose home directory should be used instead of @file{~}.
+
address@hidden
+It loads the library @file{default} (if any), unless
address@hidden is address@hidden  (This is not done in
address@hidden mode, or if @samp{-Q} or @samp{-q} was specified on the
+command line.)  The library's file name is usually @file{default.el}.
address@hidden @file{default.el}
+
address@hidden
+It runs the normal hook @code{after-init-hook}.
+
address@hidden
+It sets the major mode according to @code{initial-major-mode}, provided
+the buffer @samp{*scratch*} is still current and still in Fundamental
+mode.
+
address@hidden
+It loads the terminal-specific Lisp file, if any, except when in batch
+mode or using a window system.
+
address@hidden
+It displays the initial echo area message, unless you have suppressed
+that with @code{inhibit-startup-echo-area-message}.
+
address@hidden
+It processes the action arguments from the command line.
+
address@hidden
+It runs @code{emacs-startup-hook} and then @code{term-setup-hook}.
+
address@hidden
+It calls @code{frame-notice-user-settings}, which modifies the
+parameters of the selected frame according to whatever the init files
+specify.
+
address@hidden
+It runs @code{window-setup-hook}.  @xref{Window Systems}.
+
address@hidden
+It displays copyleft, nonwarranty, and basic use information, provided
+the value of @code{inhibit-startup-message} is @code{nil}, you didn't
+specify @samp{--no-splash} or @samp{-Q}.
address@hidden enumerate
+
address@hidden inhibit-startup-message
+This variable inhibits the initial startup messages (the nonwarranty,
+etc.).  If it is address@hidden, then the messages are not printed.
+
+This variable exists so you can set it in your personal init file, once
+you are familiar with the contents of the startup message.  Do not set
+this variable in the init file of a new user, or in a way that affects
+more than one user, because that would prevent new users from receiving
+the information they are supposed to see.
address@hidden defopt
+
address@hidden inhibit-startup-echo-area-message
+This variable controls the display of the startup echo area message.
+You can suppress the startup echo area message by adding text with this
+form to your init file:
+
address@hidden
+(setq inhibit-startup-echo-area-message
+      "@var{your-login-name}")
address@hidden example
+
+Emacs explicitly checks for an expression as shown above in your init
+file; your login name must appear in the expression as a Lisp string
+constant.  Other methods of setting
address@hidden to the same value do not
+inhibit the startup message.
+
+This way, you can easily inhibit the message for yourself if you wish,
+but thoughtless copying of your init file will not inhibit the message
+for someone else.
address@hidden defopt
+
address@hidden Init File
address@hidden The Init File, @file{.emacs}
address@hidden init file
address@hidden @file{.emacs}
+
+  When you start Emacs, it normally attempts to load your @dfn{init
+file}, a file in your home directory.  Its normal name is
address@hidden, but you can also call it @file{.emacs.el}.
+Alternatively, you can use a file named @file{init.el} in a
+subdirectory @file{.emacs.d}.  Whichever place you use, you can also
+compile the file (@pxref{Byte Compilation}); then the actual file
+loaded will be @file{.emacs.elc} or @file{init.elc}.
+
+  The command-line switches @samp{-q}, @samp{-Q}, and @samp{-u}
+control whether and where to find the init file; @samp{-q} (and the
+stronger @samp{-Q}) says not to load an init file, while @samp{-u
address@hidden says to load @var{user}'s init file instead of yours.
address@hidden Emacs,,, emacs, The GNU Emacs Manual}.  If neither
+option is specified, Emacs uses the @code{LOGNAME} environment
+variable, or the @code{USER} (most systems) or @code{USERNAME} (MS
+systems) variable, to find your home directory and thus your init
+file; this way, even if you have su'd, Emacs still loads your own init
+file.  If those environment variables are absent, though, Emacs uses
+your user-id to find your home directory.
+
address@hidden default init file
+  A site may have a @dfn{default init file}, which is the library
+named @file{default.el}.  Emacs finds the @file{default.el} file
+through the standard search path for libraries (@pxref{How Programs Do
+Loading}).  The Emacs distribution does not come with this file; sites
+may provide one for local customizations.  If the default init file
+exists, it is loaded whenever you start Emacs, except in batch mode or
+if @samp{-q} (or @samp{-Q}) is specified.  But your own personal init
+file, if any, is loaded first; if it sets @code{inhibit-default-init}
+to a address@hidden value, then Emacs does not subsequently load the
address@hidden file.
+
+  Another file for site-customization is @file{site-start.el}.  Emacs
+loads this @emph{before} the user's init file.  You can inhibit the
+loading of this file with the option @samp{--no-site-file}.
+
address@hidden site-run-file
+This variable specifies the site-customization file to load before the
+user's init file.  Its normal value is @code{"site-start"}.  The only
+way you can change it with real effect is to do so before dumping
+Emacs.
address@hidden defvar
+
+  @xref{Init Examples,, Init File Examples, emacs, The GNU Emacs Manual}, for
+examples of how to make various commonly desired customizations in your
address@hidden file.
+
address@hidden inhibit-default-init
+This variable prevents Emacs from loading the default initialization
+library file for your session of Emacs.  If its value is address@hidden,
+then the default library is not loaded.  The default value is
address@hidden
address@hidden defopt
+
address@hidden before-init-hook
+This normal hook is run, once, just before loading all the init files
+(the user's init file, @file{default.el}, and/or @file{site-start.el}).
+(The only way to change it with real effect is before dumping Emacs.)
address@hidden defvar
+
address@hidden after-init-hook
+This normal hook is run, once, just after loading all the init files
+(the user's init file, @file{default.el}, and/or @file{site-start.el}),
+before loading the terminal-specific library and processing the
+command-line action arguments.
address@hidden defvar
+
address@hidden emacs-startup-hook
+This normal hook is run, once, just after handling the command line
+arguments, just before @code{term-setup-hook}.
address@hidden defvar
+
address@hidden user-init-file
+This variable holds the absolute file name of the user's init file.  If the
+actual init file loaded is a compiled file, such as @file{.emacs.elc},
+the value refers to the corresponding source file.
address@hidden defvar
+
address@hidden user-emacs-directory
+This variable holds the name of the @file{.emacs.d} directory.  It is
+ordinarily @file{~/.emacs.d}, but differs on some platforms.
address@hidden defvar
+
address@hidden Terminal-Specific
address@hidden Terminal-Specific Initialization
address@hidden terminal-specific initialization
+
+  Each terminal type can have its own Lisp library that Emacs loads when
+run on that type of terminal.  The library's name is constructed by
+concatenating the value of the variable @code{term-file-prefix} and the
+terminal type (specified by the environment variable @code{TERM}).
+Normally, @code{term-file-prefix} has the value
address@hidden"term/"}; changing this is not recommended.  Emacs finds the file
+in the normal manner, by searching the @code{load-path} directories, and
+trying the @samp{.elc} and @samp{.el} suffixes.
+
address@hidden Termcap
+  The usual function of a terminal-specific library is to enable
+special keys to send sequences that Emacs can recognize.  It may also
+need to set or add to @code{function-key-map} if the Termcap or
+Terminfo entry does not specify all the terminal's function keys.
address@hidden Input}.
+
+  When the name of the terminal type contains a hyphen, and no library
+is found whose name is identical to the terminal's name, Emacs strips
+from the terminal's name the last hyphen and everything that follows
+it, and tries again.  This process is repeated until Emacs finds a
+matching library or until there are no more hyphens in the name (the
+latter means the terminal doesn't have any library specific to it).
+Thus, for example, if there are no @samp{aaa-48} and @samp{aaa-30}
+libraries, Emacs will try the same library @file{term/aaa.el} for
+terminal types @samp{aaa-48} and @samp{aaa-30-rv}.  If necessary, the
+library can evaluate @code{(getenv "TERM")} to find the full name of
+the terminal address@hidden
+
+  Your init file can prevent the loading of the
+terminal-specific library by setting the variable
address@hidden to @code{nil}.  This feature is useful when
+experimenting with your own peculiar customizations.
+
+  You can also arrange to override some of the actions of the
+terminal-specific library by setting the variable
address@hidden  This is a normal hook which Emacs runs using
address@hidden at the end of Emacs initialization, after loading both
+your init file and any terminal-specific libraries.  You can
+use this variable to define initializations for terminals that do not
+have their own libraries.  @xref{Hooks}.
+
address@hidden term-file-prefix
address@hidden @code{TERM} environment variable
+If the @code{term-file-prefix} variable is address@hidden, Emacs loads
+a terminal-specific initialization file as follows:
+
address@hidden
+(load (concat term-file-prefix (getenv "TERM")))
address@hidden example
+
address@hidden
+You may set the @code{term-file-prefix} variable to @code{nil} in your
+init file if you do not wish to load the
+terminal-initialization file.  To do this, put the following in
+your init file: @code{(setq term-file-prefix nil)}.
+
+On MS-DOS, if the environment variable @code{TERM} is not set, Emacs
+uses @samp{internal} as the terminal type.
address@hidden defvar
+
address@hidden term-setup-hook
+This variable is a normal hook that Emacs runs after loading your
+init file, the default initialization file (if any) and the
+terminal-specific Lisp file.
+
+You can use @code{term-setup-hook} to override the definitions made by a
+terminal-specific file.
address@hidden defvar
+
+  See @code{window-setup-hook} in @ref{Window Systems}, for a related
+feature.
+
address@hidden Command-Line Arguments
address@hidden Command-Line Arguments
address@hidden command-line arguments
+
+  You can use command-line arguments to request various actions when you
+start Emacs.  Since you do not need to start Emacs more than once per
+day, and will often leave your Emacs session running longer than that,
+command-line arguments are hardly ever used.  As a practical matter, it
+is best to avoid making the habit of using them, since this habit would
+encourage you to kill and restart Emacs unnecessarily often.  These
+options exist for two reasons: to be compatible with other editors (for
+invocation by other programs) and to enable shell scripts to run
+specific Lisp programs.
+
+  This section describes how Emacs processes command-line arguments,
+and how you can customize them.
+
address@hidden
+  (Note that some other editors require you to start afresh each time
+you want to edit a file.  With this kind of editor, you will probably
+specify the file as a command-line argument.  The recommended way to
+use GNU Emacs is to start it only once, just after you log in, and do
+all your editing in the same Emacs process.  Each time you want to edit
+a different file, you visit it with the existing Emacs, which eventually
+comes to have many files in it ready for editing.  Usually you do not
+kill the Emacs until you are about to log out.)
address@hidden ignore
+
address@hidden command-line
+This function parses the command line that Emacs was called with,
+processes it, loads the user's init file and displays the
+startup messages.
address@hidden defun
+
address@hidden command-line-processed
+The value of this variable is @code{t} once the command line has been
+processed.
+
+If you redump Emacs by calling @code{dump-emacs}, you may wish to set
+this variable to @code{nil} first in order to cause the new dumped Emacs
+to process its new command-line arguments.
address@hidden defvar
+
address@hidden command-switch-alist
address@hidden switches on command line
address@hidden options on command line
address@hidden command-line options
+The value of this variable is an alist of user-defined command-line
+options and associated handler functions.  This variable exists so you
+can add elements to it.
+
+A @dfn{command-line option} is an argument on the command line, which
+has the form:
+
address@hidden
address@hidden
address@hidden example
+
+The elements of the @code{command-switch-alist} look like this:
+
address@hidden
+(@var{option} . @var{handler-function})
address@hidden example
+
+The @sc{car}, @var{option}, is a string, the name of a command-line
+option (not including the initial hyphen).  The @var{handler-function}
+is called to handle @var{option}, and receives the option name as its
+sole argument.
+
+In some cases, the option is followed in the command line by an
+argument.  In these cases, the @var{handler-function} can find all the
+remaining command-line arguments in the variable
address@hidden  (The entire list of command-line
+arguments is in @code{command-line-args}.)
+
+The command-line arguments are parsed by the @code{command-line-1}
+function in the @file{startup.el} file.  See also @ref{Emacs
+Invocation, , Command Line Arguments for Emacs Invocation, emacs, The
+GNU Emacs Manual}.
address@hidden defvar
+
address@hidden command-line-args
+The value of this variable is the list of command-line arguments passed
+to Emacs.
address@hidden defvar
+
address@hidden command-line-functions
+This variable's value is a list of functions for handling an
+unrecognized command-line argument.  Each time the next argument to be
+processed has no special meaning, the functions in this list are called,
+in order of appearance, until one of them returns a address@hidden
+value.
+
+These functions are called with no arguments.  They can access the
+command-line argument under consideration through the variable
address@hidden, which is bound temporarily at this point.  The remaining
+arguments (not including the current one) are in the variable
address@hidden
+
+When a function recognizes and processes the argument in @code{argi}, it
+should return a address@hidden value to say it has dealt with that
+argument.  If it has also dealt with some of the following arguments, it
+can indicate that by deleting them from @code{command-line-args-left}.
+
+If all of these functions return @code{nil}, then the argument is used
+as a file name to visit.
address@hidden defvar
+
address@hidden Getting Out
address@hidden Getting Out of Emacs
address@hidden exiting Emacs
+
+  There are two ways to get out of Emacs: you can kill the Emacs job,
+which exits permanently, or you can suspend it, which permits you to
+reenter the Emacs process later.  As a practical matter, you seldom kill
+Emacs---only when you are about to log out.  Suspending is much more
+common.
+
address@hidden
+* Killing Emacs::        Exiting Emacs irreversibly.
+* Suspending Emacs::     Exiting Emacs reversibly.
address@hidden menu
+
address@hidden Killing Emacs
address@hidden  node-name,  next,  previous,  up
address@hidden Killing Emacs
address@hidden killing Emacs
+
+  Killing Emacs means ending the execution of the Emacs process.  The
+parent process normally resumes control.  The low-level primitive for
+killing Emacs is @code{kill-emacs}.
+
address@hidden kill-emacs &optional exit-data
+This function exits the Emacs process and kills it.
+
+If @var{exit-data} is an integer, then it is used as the exit status
+of the Emacs process.  (This is useful primarily in batch operation; see
address@hidden Mode}.)
+
+If @var{exit-data} is a string, its contents are stuffed into the
+terminal input buffer so that the shell (or whatever program next reads
+input) can read them.
address@hidden defun
+
+  All the information in the Emacs process, aside from files that have
+been saved, is lost when the Emacs process is killed.  Because killing
+Emacs inadvertently can lose a lot of work, Emacs queries for
+confirmation before actually terminating if you have buffers that need
+saving or subprocesses that are running.  This is done in the function
address@hidden, the higher level function from which
address@hidden is usually called.
+
address@hidden kill-emacs-query-functions
+After asking the standard questions, @code{save-buffers-kill-emacs}
+calls the functions in the list @code{kill-emacs-query-functions}, in
+order of appearance, with no arguments.  These functions can ask for
+additional confirmation from the user.  If any of them returns
address@hidden, @code{save-buffers-kill-emacs} does not kill Emacs, and
+does not run the remaining functions in this hook.  Calling
address@hidden directly does not run this hook.
address@hidden defvar
+
address@hidden kill-emacs-hook
+This variable is a normal hook; once @code{save-buffers-kill-emacs} is
+finished with all file saving and confirmation, it calls
address@hidden which runs the functions in this hook.
address@hidden does not run this hook in batch mode.
+
address@hidden may be invoked directly (that is not via
address@hidden) if the terminal is disconnected, or in
+similar situations where interaction with the user is not possible.
+Thus, if your hook needs to interact with the user, put it on
address@hidden; if it needs to run regardless of
+how Emacs is killed, put it on @code{kill-emacs-hook}.
address@hidden defvar
+
address@hidden Suspending Emacs
address@hidden Suspending Emacs
address@hidden suspending Emacs
+
+  @dfn{Suspending Emacs} means stopping Emacs temporarily and returning
+control to its superior process, which is usually the shell.  This
+allows you to resume editing later in the same Emacs process, with the
+same buffers, the same kill ring, the same undo history, and so on.  To
+resume Emacs, use the appropriate command in the parent shell---most
+likely @code{fg}.
+
+  Some operating systems do not support suspension of jobs; on these
+systems, ``suspension'' actually creates a new shell temporarily as a
+subprocess of Emacs.  Then you would exit the shell to return to Emacs.
+
+  Suspension is not useful with window systems, because the Emacs job
+may not have a parent that can resume it again, and in any case you can
+give input to some other job such as a shell merely by moving to a
+different window.  Therefore, suspending is not allowed when Emacs is using
+a window system (X, MS Windows, or Mac).
+
address@hidden suspend-emacs &optional string
+This function stops Emacs and returns control to the superior process.
+If and when the superior process resumes Emacs, @code{suspend-emacs}
+returns @code{nil} to its caller in Lisp.
+
+If @var{string} is address@hidden, its characters are sent to be read
+as terminal input by Emacs's superior shell.  The characters in
address@hidden are not echoed by the superior shell; only the results
+appear.
+
+Before suspending, @code{suspend-emacs} runs the normal hook
address@hidden
+
+After the user resumes Emacs, @code{suspend-emacs} runs the normal hook
address@hidden  @xref{Hooks}.
+
+The next redisplay after resumption will redraw the entire screen,
+unless the variable @code{no-redraw-on-reenter} is address@hidden
+(@pxref{Refresh Screen}).
+
+In the following example, note that @samp{pwd} is not echoed after
+Emacs is suspended.  But it is read and executed by the shell.
+
address@hidden
address@hidden
+(suspend-emacs)
+     @result{} nil
address@hidden group
+
address@hidden
+(add-hook 'suspend-hook
+          (function (lambda ()
+                      (or (y-or-n-p
+                            "Really suspend? ")
+                          (error "Suspend canceled")))))
+     @result{} (lambda nil
+          (or (y-or-n-p "Really suspend? ")
+              (error "Suspend canceled")))
address@hidden group
address@hidden
+(add-hook 'suspend-resume-hook
+          (function (lambda () (message "Resumed!"))))
+     @result{} (lambda nil (message "Resumed!"))
address@hidden group
address@hidden
+(suspend-emacs "pwd")
+     @result{} nil
address@hidden group
address@hidden
+---------- Buffer: Minibuffer ----------
+Really suspend? @kbd{y}
+---------- Buffer: Minibuffer ----------
address@hidden group
+
address@hidden
+---------- Parent Shell ----------
+lewis@@slug[23] % /user/lewis/manual
+lewis@@slug[24] % fg
address@hidden group
+
address@hidden
+---------- Echo Area ----------
+Resumed!
address@hidden group
address@hidden smallexample
address@hidden defun
+
address@hidden suspend-hook
+This variable is a normal hook that Emacs runs before suspending.
address@hidden defvar
+
address@hidden suspend-resume-hook
+This variable is a normal hook that Emacs runs on resuming
+after a suspension.
address@hidden defvar
+
address@hidden System Environment
address@hidden Operating System Environment
address@hidden operating system environment
+
+  Emacs provides access to variables in the operating system environment
+through various functions.  These variables include the name of the
+system, the user's @acronym{UID}, and so on.
+
address@hidden system-configuration
+This variable holds the standard GNU configuration name for the
+hardware/software configuration of your system, as a string.  The
+convenient way to test parts of this string is with
address@hidden
address@hidden defvar
+
address@hidden system type and name
address@hidden system-type
+The value of this variable is a symbol indicating the type of operating
+system Emacs is operating on.  Here is a table of the possible values:
+
address@hidden @code
address@hidden alpha-vms
+VMS on the Alpha.
+
address@hidden aix-v3
+AIX.
+
address@hidden berkeley-unix
+Berkeley BSD.
+
address@hidden cygwin
+Cygwin.
+
address@hidden dgux
+Data General DGUX operating system.
+
address@hidden gnu
+the GNU system (using the GNU kernel, which consists of the HURD and Mach).
+
address@hidden gnu/linux
+A GNU/Linux system---that is, a variant GNU system, using the Linux
+kernel.  (These systems are the ones people often call ``Linux,'' but
+actually Linux is just the kernel, not the whole system.)
+
address@hidden hpux
+Hewlett-Packard HPUX operating system.
+
address@hidden irix
+Silicon Graphics Irix system.
+
address@hidden ms-dos
+Microsoft MS-DOS ``operating system.''  Emacs compiled with DJGPP for
+MS-DOS binds @code{system-type} to @code{ms-dos} even when you run it on
+MS-Windows.
+
address@hidden next-mach
+NeXT Mach-based system.
+
address@hidden rtu
+Masscomp RTU, UCB universe.
+
address@hidden unisoft-unix
+UniSoft UniPlus.
+
address@hidden usg-unix-v
+AT&T System V.
+
address@hidden vax-vms
+VAX VMS.
+
address@hidden windows-nt
+Microsoft windows NT.  The same executable supports Windows 9X, but the
+value of @code{system-type} is @code{windows-nt} in either case.
+
address@hidden xenix
+SCO Xenix 386.
address@hidden table
+
+We do not wish to add new symbols to make finer distinctions unless it
+is absolutely necessary!  In fact, we hope to eliminate some of these
+alternatives in the future.  We recommend using
address@hidden to distinguish between different operating
+systems.
address@hidden defvar
+
address@hidden system-name
+This function returns the name of the machine you are running on.
address@hidden
+(system-name)
+     @result{} "www.gnu.org"
address@hidden example
address@hidden defun
+
+  The symbol @code{system-name} is a variable as well as a function.  In
+fact, the function returns whatever value the variable
address@hidden currently holds.  Thus, you can set the variable
address@hidden in case Emacs is confused about the name of your
+system.  The variable is also useful for constructing frame titles
+(@pxref{Frame Titles}).
+
address@hidden mail-host-address
+If this variable is address@hidden, it is used instead of
address@hidden for purposes of generating email addresses.  For
+example, it is used when constructing the default value of
address@hidden  @xref{User Identification}.  (Since this is
+done when Emacs starts up, the value actually used is the one saved when
+Emacs was dumped.  @xref{Building Emacs}.)
address@hidden defvar
+
address@hidden Command getenv var
address@hidden environment variable access
+This function returns the value of the environment variable @var{var},
+as a string.  @var{var} should be a string.  If @var{var} is undefined
+in the environment, @code{getenv} returns @code{nil}.  If returns
address@hidden""} if @var{var} is set but null.  Within Emacs, the environment
+variable values are kept in the Lisp variable @code{process-environment}.
+
address@hidden
address@hidden
+(getenv "USER")
+     @result{} "lewis"
address@hidden group
+
address@hidden
+lewis@@slug[10] % printenv
+PATH=.:/user/lewis/bin:/usr/bin:/usr/local/bin
+USER=lewis
address@hidden group
address@hidden
+TERM=ibmapa16
+SHELL=/bin/csh
+HOME=/user/lewis
address@hidden group
address@hidden example
address@hidden deffn
+
address@hidden Emacs 19 feature
address@hidden Command setenv variable &optional value
+This command sets the value of the environment variable named
address@hidden to @var{value}.  @var{variable} should be a string.
+Internally, Emacs Lisp can handle any string.  However, normally
address@hidden should be a valid shell identifier, that is, a sequence
+of letters, digits and underscores, starting with a letter or
+underscore.  Otherwise, errors may occur if subprocesses of Emacs try
+to access the value of @var{variable}.  If @var{value} is omitted or
address@hidden, @code{setenv} removes @var{variable} from the environment.
+Otherwise, @var{value} should be a string.
+
address@hidden works by modifying @code{process-environment}; binding
+that variable with @code{let} is also reasonable practice.
+
address@hidden returns the new value of @var{variable}, or @code{nil}
+if it removed @var{variable} from the environment.
address@hidden deffn
+
address@hidden process-environment
+This variable is a list of strings, each describing one environment
+variable.  The functions @code{getenv} and @code{setenv} work by means
+of this variable.
+
address@hidden
address@hidden
+process-environment
address@hidden ("l=/usr/stanford/lib/gnuemacs/lisp"
+    "PATH=.:/user/lewis/bin:/usr/class:/nfsusr/local/bin"
+    "USER=lewis"
address@hidden group
address@hidden
+    "TERM=ibmapa16"
+    "SHELL=/bin/csh"
+    "HOME=/user/lewis")
address@hidden group
address@hidden smallexample
+
+If @code{process-environment} contains ``duplicate'' elements that
+specify the same environment variable, the first of these elements
+specifies the variable, and the other ``duplicates'' are ignored.
address@hidden defvar
+
address@hidden path-separator
+This variable holds a string which says which character separates
+directories in a search path (as found in an environment variable).  Its
+value is @code{":"} for Unix and GNU systems, and @code{";"} for MS-DOS
+and MS-Windows.
address@hidden defvar
+
address@hidden parse-colon-path path
+This function takes a search path string such as would be the value of
+the @code{PATH} environment variable, and splits it at the separators,
+returning a list of directory names.  @code{nil} in this list stands for
+``use the current directory.''  Although the function's name says
+``colon,'' it actually uses the value of @code{path-separator}.
+
address@hidden
+(parse-colon-path ":/foo:/bar")
+     @result{} (nil "/foo/" "/bar/")
address@hidden example
address@hidden defun
+
address@hidden invocation-name
+This variable holds the program name under which Emacs was invoked.  The
+value is a string, and does not include a directory name.
address@hidden defvar
+
address@hidden invocation-directory
+This variable holds the directory from which the Emacs executable was
+invoked, or perhaps @code{nil} if that directory cannot be determined.
address@hidden defvar
+
address@hidden installation-directory
+If address@hidden, this is a directory within which to look for the
address@hidden and @file{etc} subdirectories.  This is address@hidden
+when Emacs can't find those directories in their standard installed
+locations, but can find them in a directory related somehow to the one
+containing the Emacs executable.
address@hidden defvar
+
address@hidden load-average &optional use-float
+This function returns the current 1-minute, 5-minute, and 15-minute load
+averages, in a list.
+
+By default, the values are integers that are 100 times the system load
+averages, which indicate the average number of processes trying to run.
+If @var{use-float} is address@hidden, then they are returned
+as floating point numbers and without multiplying by 100.
+
+If it is impossible to obtain the load average, this function signals
+an error.  On some platforms, access to load averages requires
+installing Emacs as setuid or setgid so that it can read kernel
+information, and that usually isn't advisable.
+
+If the 1-minute load average is available, but the 5- or 15-minute
+averages are not, this function returns a shortened list containing
+the available averages.
+
address@hidden
address@hidden
+(load-average)
+     @result{} (169 48 36)
address@hidden group
address@hidden
+(load-average t)
+     @result{} (1.69 0.48 0.36)
address@hidden group
+
address@hidden
+lewis@@rocky[5] % uptime
+ 11:55am  up 1 day, 19:37,  3 users,
+ load average: 1.69, 0.48, 0.36
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden emacs-pid
+This function returns the process @acronym{ID} of the Emacs process,
+as an integer.
address@hidden defun
+
address@hidden tty-erase-char
+This variable holds the erase character that was selected
+in the system's terminal driver, before Emacs was started.
+The value is @code{nil} if Emacs is running under a window system.
address@hidden defvar
+
address@hidden setprv privilege-name &optional setp getprv
+This function sets or resets a VMS privilege.  (It does not exist on
+other systems.)  The first argument is the privilege name, as a string.
+The second argument, @var{setp}, is @code{t} or @code{nil}, indicating
+whether the privilege is to be turned on or off.  Its default is
address@hidden  The function returns @code{t} if successful, @code{nil}
+otherwise.
+
+If the third argument, @var{getprv}, is address@hidden, @code{setprv}
+does not change the privilege, but returns @code{t} or @code{nil}
+indicating whether the privilege is currently enabled.
address@hidden defun
+
address@hidden User Identification
address@hidden User Identification
address@hidden user identification
+
address@hidden init-file-user
+This variable says which user's init files should be used by
+Emacs---or @code{nil} if none.  @code{""} stands for the user who
+originally logged in.  The value reflects command-line options such as
address@hidden or @samp{-u @var{user}}.
+
+Lisp packages that load files of customizations, or any other sort of
+user profile, should obey this variable in deciding where to find it.
+They should load the profile of the user name found in this variable.
+If @code{init-file-user} is @code{nil}, meaning that the @samp{-q}
+option was used, then Lisp packages should not load any customization
+files or user profile.
address@hidden defvar
+
address@hidden user-mail-address
+This holds the nominal email address of the user who is using Emacs.
+Emacs normally sets this variable to a default value after reading your
+init files, but not if you have already set it.  So you can set the
+variable to some other value in your init file if you do not
+want to use the default value.
address@hidden defvar
+
address@hidden user-login-name &optional uid
+If you don't specify @var{uid}, this function returns the name under
+which the user is logged in.  If the environment variable @code{LOGNAME}
+is set, that value is used.  Otherwise, if the environment variable
address@hidden is set, that value is used.  Otherwise, the value is based
+on the effective @acronym{UID}, not the real @acronym{UID}.
+
+If you specify @var{uid}, the value is the user name that corresponds
+to @var{uid} (which should be an integer), or @code{nil} if there is
+no such user.
+
address@hidden
address@hidden
+(user-login-name)
+     @result{} "lewis"
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden user-real-login-name
+This function returns the user name corresponding to Emacs's real
address@hidden  This ignores the effective @acronym{UID} and ignores the
+environment variables @code{LOGNAME} and @code{USER}.
address@hidden defun
+
address@hidden user-full-name &optional uid
+This function returns the full name of the logged-in user---or the value
+of the environment variable @code{NAME}, if that is set.
+
address@hidden "Bil" is the correct spelling.
address@hidden
address@hidden
+(user-full-name)
+     @result{} "Bil Lewis"
address@hidden group
address@hidden example
+
+If the Emacs job's user-id does not correspond to any known user (and
+provided @code{NAME} is not set), the value is @code{"unknown"}.
+
+If @var{uid} is address@hidden, then it should be a number (a user-id)
+or a string (a login name).  Then @code{user-full-name} returns the full
+name corresponding to that user-id or login name.  If you specify a
+user-id or login name that isn't defined, it returns @code{nil}.
address@hidden defun
+
address@hidden user-full-name
address@hidden user-real-login-name
address@hidden user-login-name
+  The symbols @code{user-login-name}, @code{user-real-login-name} and
address@hidden are variables as well as functions.  The functions
+return the same values that the variables hold.  These variables allow
+you to ``fake out'' Emacs by telling the functions what to return.  The
+variables are also useful for constructing frame titles (@pxref{Frame
+Titles}).
+
address@hidden user-real-uid
+This function returns the real @acronym{UID} of the user.
+The value may be a floating point number.
+
address@hidden
address@hidden
+(user-real-uid)
+     @result{} 19
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden user-uid
+This function returns the effective @acronym{UID} of the user.
+The value may be a floating point number.
address@hidden defun
+
address@hidden Time of Day
address@hidden Time of Day
+
+  This section explains how to determine the current time and the time
+zone.
+
address@hidden current-time-string &optional time-value
+This function returns the current time and date as a human-readable
+string.  The format of the string is unvarying; the number of characters
+used for each part is always the same, so you can reliably use
address@hidden to extract pieces of it.  It is wise to count the
+characters from the beginning of the string rather than from the end, as
+additional information may some day be added at the end.
+
address@hidden Emacs 19 feature
+The argument @var{time-value}, if given, specifies a time to format
+instead of the current time.  The argument should be a list whose first
+two elements are integers.  Thus, you can use times obtained from
address@hidden (see below) and from @code{file-attributes}
+(@pxref{Definition of file-attributes}).  @var{time-value} can also be
+a cons of two integers, but this is considered obsolete.
+
address@hidden
address@hidden
+(current-time-string)
+     @result{} "Wed Oct 14 22:21:05 1987"
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden Emacs 19 feature
address@hidden current-time
+This function returns the system's time value as a list of three
+integers: @code{(@var{high} @var{low} @var{microsec})}.  The integers
address@hidden and @var{low} combine to give the number of seconds since
+0:00 January 1, 1970 UTC (Coordinated Universal Time), which is
address@hidden
address@hidden * 2**16 + @var{low}.
address@hidden ifnottex
address@hidden
+$high*2^{16}+low$.
address@hidden tex
+
+The third element, @var{microsec}, gives the microseconds since the
+start of the current second (or 0 for systems that return time with
+the resolution of only one second).
+
+The first two elements can be compared with file time values such as you
+get with the function @code{file-attributes}.
address@hidden of file-attributes}.
address@hidden defun
+
address@hidden Emacs 19 feature
address@hidden current-time-zone &optional time-value
+This function returns a list describing the time zone that the user is
+in.
+
+The value has the form @code{(@var{offset} @var{name})}.  Here
address@hidden is an integer giving the number of seconds ahead of UTC
+(east of Greenwich).  A negative value means west of Greenwich.  The
+second element, @var{name}, is a string giving the name of the time
+zone.  Both elements change when daylight saving time begins or ends;
+if the user has specified a time zone that does not use a seasonal time
+adjustment, then the value is constant through time.
+
+If the operating system doesn't supply all the information necessary to
+compute the value, the unknown elements of the list are @code{nil}.
+
+The argument @var{time-value}, if given, specifies a time to analyze
+instead of the current time.  The argument should have the same form
+as for @code{current-time-string} (see above).  Thus, you can use
+times obtained from @code{current-time} (see above) and from
address@hidden  @xref{Definition of file-attributes}.
address@hidden defun
+
address@hidden set-time-zone-rule tz
+This function specifies the local time zone according to @var{tz}.  If
address@hidden is @code{nil}, that means to use an implementation-defined
+default time zone.  If @var{tz} is @code{t}, that means to use
+Universal Time.  Otherwise, @var{tz} should be a string specifying a
+time zone rule.
address@hidden defun
+
address@hidden float-time &optional time-value
+This function returns the current time as a floating-point number of
+seconds since the epoch.  The argument @var{time-value}, if given,
+specifies a time to convert instead of the current time.  The argument
+should have the same form as for @code{current-time-string} (see
+above).  Thus, it accepts the output of @code{current-time} and
address@hidden
+
address@hidden: Since the result is floating point, it may not be
+exact.  Do not use this function if precise time stamps are required.
address@hidden defun
+
address@hidden Time Conversion
address@hidden Time Conversion
+
+  These functions convert time values (lists of two or three integers)
+to calendrical information and vice versa.  You can get time values
+from the functions @code{current-time} (@pxref{Time of Day}) and
address@hidden (@pxref{Definition of file-attributes}).
+
+  Many operating systems are limited to time values that contain 32 bits
+of information; these systems typically handle only the times from
+1901-12-13 20:45:52 UTC through 2038-01-19 03:14:07 UTC.  However, some
+operating systems have larger time values, and can represent times far
+in the past or future.
+
+  Time conversion functions always use the Gregorian calendar, even
+for dates before the Gregorian calendar was introduced.  Year numbers
+count the number of years since the year 1 B.C., and do not skip zero
+as traditional Gregorian years do; for example, the year number
address@hidden represents the Gregorian year 38 address@hidden
+
address@hidden decode-time &optional time
+This function converts a time value into calendrical information.  If
+you don't specify @var{time}, it decodes the current time.  The return
+value is a list of nine elements, as follows:
+
address@hidden
+(@var{seconds} @var{minutes} @var{hour} @var{day} @var{month} @var{year} 
@var{dow} @var{dst} @var{zone})
address@hidden example
+
+Here is what the elements mean:
+
address@hidden @var
address@hidden seconds
+The number of seconds past the minute, as an integer between 0 and 59.
+On some operating systems, this is 60 for leap seconds.
address@hidden minutes
+The number of minutes past the hour, as an integer between 0 and 59.
address@hidden hour
+The hour of the day, as an integer between 0 and 23.
address@hidden day
+The day of the month, as an integer between 1 and 31.
address@hidden month
+The month of the year, as an integer between 1 and 12.
address@hidden year
+The year, an integer typically greater than 1900.
address@hidden dow
+The day of week, as an integer between 0 and 6, where 0 stands for
+Sunday.
address@hidden dst
address@hidden if daylight saving time is effect, otherwise @code{nil}.
address@hidden zone
+An integer indicating the time zone, as the number of seconds east of
+Greenwich.
address@hidden table
+
address@hidden Lisp Note:} Common Lisp has different meanings for
address@hidden and @var{zone}.
address@hidden defun
+
address@hidden encode-time seconds minutes hour day month year &optional zone
+This function is the inverse of @code{decode-time}.  It converts seven
+items of calendrical data into a time value.  For the meanings of the
+arguments, see the table above under @code{decode-time}.
+
+Year numbers less than 100 are not treated specially.  If you want them
+to stand for years above 1900, or years above 2000, you must alter them
+yourself before you call @code{encode-time}.
+
+The optional argument @var{zone} defaults to the current time zone and
+its daylight saving time rules.  If specified, it can be either a list
+(as you would get from @code{current-time-zone}), a string as in the
address@hidden environment variable, @code{t} for Universal Time, or an
+integer (as you would get from @code{decode-time}).  The specified
+zone is used without any further alteration for daylight saving time.
+
+If you pass more than seven arguments to @code{encode-time}, the first
+six are used as @var{seconds} through @var{year}, the last argument is
+used as @var{zone}, and the arguments in between are ignored.  This
+feature makes it possible to use the elements of a list returned by
address@hidden as the arguments to @code{encode-time}, like this:
+
address@hidden
+(apply 'encode-time (decode-time @dots{}))
address@hidden example
+
+You can perform simple date arithmetic by using out-of-range values for
+the @var{seconds}, @var{minutes}, @var{hour}, @var{day}, and @var{month}
+arguments; for example, day 0 means the day preceding the given month.
+
+The operating system puts limits on the range of possible time values;
+if you try to encode a time that is out of range, an error results.
+For instance, years before 1970 do not work on some systems;
+on others, years as early as 1901 do work.
address@hidden defun
+
address@hidden Time Parsing
address@hidden Parsing and Formatting Times
+
+  These functions convert time values (lists of two or three integers)
+to text in a string, and vice versa.
+
address@hidden date-to-time string
+This function parses the time-string @var{string} and returns the
+corresponding time value.
address@hidden defun
+
address@hidden format-time-string format-string &optional time universal
+This function converts @var{time} (or the current time, if @var{time} is
+omitted) to a string according to @var{format-string}.  The argument
address@hidden may contain @samp{%}-sequences which say to
+substitute parts of the time.  Here is a table of what the
address@hidden mean:
+
address@hidden @samp
address@hidden %a
+This stands for the abbreviated name of the day of week.
address@hidden %A
+This stands for the full name of the day of week.
address@hidden %b
+This stands for the abbreviated name of the month.
address@hidden %B
+This stands for the full name of the month.
address@hidden %c
+This is a synonym for @samp{%x %X}.
address@hidden %C
+This has a locale-specific meaning.  In the default locale (named C), it
+is equivalent to @samp{%A, %B %e, %Y}.
address@hidden %d
+This stands for the day of month, zero-padded.
address@hidden %D
+This is a synonym for @samp{%m/%d/%y}.
address@hidden %e
+This stands for the day of month, blank-padded.
address@hidden %h
+This is a synonym for @samp{%b}.
address@hidden %H
+This stands for the hour (00-23).
address@hidden %I
+This stands for the hour (01-12).
address@hidden %j
+This stands for the day of the year (001-366).
address@hidden %k
+This stands for the hour (0-23), blank padded.
address@hidden %l
+This stands for the hour (1-12), blank padded.
address@hidden %m
+This stands for the month (01-12).
address@hidden %M
+This stands for the minute (00-59).
address@hidden %n
+This stands for a newline.
address@hidden %p
+This stands for @samp{AM} or @samp{PM}, as appropriate.
address@hidden %r
+This is a synonym for @samp{%I:%M:%S %p}.
address@hidden %R
+This is a synonym for @samp{%H:%M}.
address@hidden %S
+This stands for the seconds (00-59).
address@hidden %t
+This stands for a tab character.
address@hidden %T
+This is a synonym for @samp{%H:%M:%S}.
address@hidden %U
+This stands for the week of the year (01-52), assuming that weeks
+start on Sunday.
address@hidden %w
+This stands for the numeric day of week (0-6).  Sunday is day 0.
address@hidden %W
+This stands for the week of the year (01-52), assuming that weeks
+start on Monday.
address@hidden %x
+This has a locale-specific meaning.  In the default locale (named
address@hidden), it is equivalent to @samp{%D}.
address@hidden %X
+This has a locale-specific meaning.  In the default locale (named
address@hidden), it is equivalent to @samp{%T}.
address@hidden %y
+This stands for the year without century (00-99).
address@hidden %Y
+This stands for the year with century.
address@hidden %Z
+This stands for the time zone abbreviation (e.g., @samp{EST}).
address@hidden %z
+This stands for the time zone numerical offset (e.g., @samp{-0500}).
address@hidden table
+
+You can also specify the field width and type of padding for any of
+these @samp{%}-sequences.  This works as in @code{printf}: you write
+the field width as digits in the middle of a @samp{%}-sequences.  If you
+start the field width with @samp{0}, it means to pad with zeros.  If you
+start the field width with @samp{_}, it means to pad with spaces.
+
+For example, @samp{%S} specifies the number of seconds since the minute;
address@hidden means to pad this with zeros to 3 positions, @samp{%_3S} to
+pad with spaces to 3 positions.  Plain @samp{%3S} pads with zeros,
+because that is how @samp{%S} normally pads to two positions.
+
+The characters @samp{E} and @samp{O} act as modifiers when used between
address@hidden and one of the letters in the table above.  @samp{E} specifies
+using the current locale's ``alternative'' version of the date and time.
+In a Japanese locale, for example, @code{%Ex} might yield a date format
+based on the Japanese Emperors' reigns.  @samp{E} is allowed in
address@hidden, @samp{%EC}, @samp{%Ex}, @samp{%EX}, @samp{%Ey}, and
address@hidden
+
address@hidden means to use the current locale's ``alternative''
+representation of numbers, instead of the ordinary decimal digits.  This
+is allowed with most letters, all the ones that output numbers.
+
+If @var{universal} is address@hidden, that means to describe the time as
+Universal Time; @code{nil} means describe it using what Emacs believes
+is the local time zone (see @code{current-time-zone}).
+
+This function uses the C library function @code{strftime}
+(@pxref{Formatting Calendar Time,,, libc, The GNU C Library Reference
+Manual}) to do most of the work.  In order to communicate with that
+function, it first encodes its argument using the coding system
+specified by @code{locale-coding-system} (@pxref{Locales}); after
address@hidden returns the resulting string,
address@hidden decodes the string using that same coding
+system.
address@hidden defun
+
address@hidden seconds-to-time seconds
+This function converts @var{seconds}, a floating point number of
+seconds since the epoch, to a time value and returns that.  To perform
+the inverse conversion, use @code{float-time}.
address@hidden defun
+
address@hidden Processor Run Time
address@hidden Processor Run time
address@hidden processor run time
+
address@hidden get-internal-run-time
+This function returns the processor run time used by Emacs as a list
+of three integers: @code{(@var{high} @var{low} @var{microsec})}.  The
+integers @var{high} and @var{low} combine to give the number of
+seconds, which is
address@hidden
address@hidden * 2**16 + @var{low}.
address@hidden ifnottex
address@hidden
+$high*2^{16}+low$.
address@hidden tex
+
+The third element, @var{microsec}, gives the microseconds (or 0 for
+systems that return time with the resolution of only one second).
+
+If the system doesn't provide a way to determine the processor run
+time, get-internal-run-time returns the same time as current-time.
address@hidden defun
+
address@hidden Time Calculations
address@hidden Time Calculations
+
+  These functions perform calendrical computations using time values
+(the kind of list that @code{current-time} returns).
+
address@hidden time-less-p t1 t2
+This returns @code{t} if time value @var{t1} is less than time value
address@hidden
address@hidden defun
+
address@hidden time-subtract t1 t2
+This returns the time difference @var{t1} @minus{} @var{t2} between
+two time values, in the same format as a time value.
address@hidden defun
+
address@hidden time-add t1 t2
+This returns the sum of two time values, one of which ought to
+represent a time difference rather than a point in time.
+Here is how to add a number of seconds to a time value:
+
address@hidden
+(time-add @var{time} (seconds-to-time @var{seconds}))
address@hidden example
address@hidden defun
+
address@hidden time-to-days time
+This function returns the number of days between the beginning of year
+1 and @var{time}.
address@hidden defun
+
address@hidden time-to-day-in-year time
+This returns the day number within the year corresponding to @var{time}.
address@hidden defun
+
address@hidden date-leap-year-p year
+This function returns @code{t} if @var{year} is a leap year.
address@hidden defun
+
address@hidden Timers
address@hidden Timers for Delayed Execution
address@hidden timer
+
+  You can set up a @dfn{timer} to call a function at a specified
+future time or after a certain length of idleness.
+
+  Emacs cannot run timers at any arbitrary point in a Lisp program; it
+can run them only when Emacs could accept output from a subprocess:
+namely, while waiting or inside certain primitive functions such as
address@hidden or @code{read-event} which @emph{can} wait.  Therefore, a
+timer's execution may be delayed if Emacs is busy.  However, the time of
+execution is very precise if Emacs is idle.
+
+  Emacs binds @code{inhibit-quit} to @code{t} before calling the timer
+function, because quitting out of many timer functions can leave
+things in an inconsistent state.  This is normally unproblematical
+because most timer functions don't do a lot of work.  Indeed, for a
+timer to call a function that takes substantial time to run is likely
+to be annoying.  If a timer function needs to allow quitting, it
+should use @code{with-local-quit} (@pxref{Quitting}).  For example, if
+a timer function calls @code{accept-process-output} to receive output
+from an external process, that call should be wrapped inside
address@hidden, to ensure that @kbd{C-g} works if the external
+process hangs.
+
+  It is usually a bad idea for timer functions to alter buffer
+contents.  When they do, they usually should call @code{undo-boundary}
+both before and after changing the buffer, to separate the timer's
+changes from user commands' changes and prevent a single undo entry
+from growing to be quite large.
+
+  Timer functions should also avoid calling functions that cause Emacs
+to wait, such as @code{sit-for} (@pxref{Waiting}).  This can lead to
+unpredictable effects, since other timers (or even the same timer) can
+run while waiting.  If a timer function needs to perform an action
+after a certain time has elapsed, it can do this by scheduling a new
+timer.
+
+  If a timer function calls functions that can change the match data,
+it should save and restore the match data.  @xref{Saving Match Data}.
+
address@hidden Command run-at-time time repeat function &rest args
+This sets up a timer that calls the function @var{function} with
+arguments @var{args} at time @var{time}.  If @var{repeat} is a number
+(integer or floating point), the timer is scheduled to run again every
address@hidden seconds after @var{time}.  If @var{repeat} is @code{nil},
+the timer runs only once.
+
address@hidden may specify an absolute or a relative time.
+
+Absolute times may be specified using a string with a limited variety
+of formats, and are taken to be times @emph{today}, even if already in
+the past.  The recognized forms are @address@hidden,
address@hidden@var{x}:@var{xx}}, or @address@hidden:@var{xx}} (military time),
+and @address@hidden, @address@hidden, @address@hidden,
address@hidden@var{xx}PM}, @address@hidden:@var{xx}am},
address@hidden@var{xx}:@var{xx}AM}, @address@hidden:@var{xx}pm}, or
address@hidden@var{xx}:@var{xx}PM}.  A period can be used instead of a colon
+to separate the hour and minute parts.
+
+To specify a relative time as a string, use numbers followed by units.
+For example:
+
address@hidden @samp
address@hidden 1 min
+denotes 1 minute from now.
address@hidden 1 min 5 sec
+denotes 65 seconds from now.
address@hidden 1 min 2 sec 3 hour 4 day 5 week 6 fortnight 7 month 8 year
+denotes exactly 103 months, 123 days, and 10862 seconds from now.
address@hidden table
+
+For relative time values, Emacs considers a month to be exactly thirty
+days, and a year to be exactly 365.25 days.
+
+Not all convenient formats are strings.  If @var{time} is a number
+(integer or floating point), that specifies a relative time measured in
+seconds.  The result of @code{encode-time} can also be used to specify
+an absolute value for @var{time}.
+
+In most cases, @var{repeat} has no effect on when @emph{first} call
+takes address@hidden alone specifies that.  There is one exception:
+if @var{time} is @code{t}, then the timer runs whenever the time is a
+multiple of @var{repeat} seconds after the epoch.  This is useful for
+functions like @code{display-time}.
+
+The function @code{run-at-time} returns a timer value that identifies
+the particular scheduled future action.  You can use this value to call
address@hidden (see below).
address@hidden deffn
+
+  A repeating timer nominally ought to run every @var{repeat} seconds,
+but remember that any invocation of a timer can be late.  Lateness of
+one repetition has no effect on the scheduled time of the next
+repetition.  For instance, if Emacs is busy computing for long enough
+to cover three scheduled repetitions of the timer, and then starts to
+wait, it will immediately call the timer function three times in
+immediate succession (presuming no other timers trigger before or
+between them).  If you want a timer to run again no less than @var{n}
+seconds after the last invocation, don't use the @var{repeat} argument.
+Instead, the timer function should explicitly reschedule the timer.
+
address@hidden timer-max-repeats
+This variable's value specifies the maximum number of times to repeat
+calling a timer function in a row, when many previously scheduled
+calls were unavoidably delayed.
address@hidden defvar
+
address@hidden with-timeout (seconds address@hidden) address@hidden
+Execute @var{body}, but give up after @var{seconds} seconds.  If
address@hidden finishes before the time is up, @code{with-timeout} returns
+the value of the last form in @var{body}.  If, however, the execution of
address@hidden is cut short by the timeout, then @code{with-timeout}
+executes all the @var{timeout-forms} and returns the value of the last
+of them.
+
+This macro works by setting a timer to run after @var{seconds} seconds.  If
address@hidden finishes before that time, it cancels the timer.  If the
+timer actually runs, it terminates execution of @var{body}, then
+executes @var{timeout-forms}.
+
+Since timers can run within a Lisp program only when the program calls a
+primitive that can wait, @code{with-timeout} cannot stop executing
address@hidden while it is in the midst of a computation---only when it
+calls one of those primitives.  So use @code{with-timeout} only with a
address@hidden that waits for input, not one that does a long computation.
address@hidden defmac
+
+  The function @code{y-or-n-p-with-timeout} provides a simple way to use
+a timer to avoid waiting too long for an answer.  @xref{Yes-or-No
+Queries}.
+
address@hidden cancel-timer timer
+This cancels the requested action for @var{timer}, which should be a
+timer---usually, one previously returned by @code{run-at-time} or
address@hidden  This cancels the effect of that call to
+one of these functions; the arrival of the specified time will not
+cause anything special to happen.
address@hidden defun
+
address@hidden Idle Timers
address@hidden Idle Timers
+
+  Here is how to set up a timer that runs when Emacs is idle for a
+certain length of time.  Aside from how to set them up, idle timers
+work just like ordinary timers.
+
address@hidden Command run-with-idle-timer secs repeat function &rest args
+Set up a timer which runs when Emacs has been idle for @var{secs}
+seconds.  The value of @var{secs} may be an integer or a floating point
+number; a value of the type returned by @code{current-idle-time}
+is also allowed.
+
+If @var{repeat} is @code{nil}, the timer runs just once, the first time
+Emacs remains idle for a long enough time.  More often @var{repeat} is
address@hidden, which means to run the timer @emph{each time} Emacs
+remains idle for @var{secs} seconds.
+
+The function @code{run-with-idle-timer} returns a timer value which you
+can use in calling @code{cancel-timer} (@pxref{Timers}).
address@hidden deffn
+
address@hidden idleness
+  Emacs becomes ``idle'' when it starts waiting for user input, and it
+remains idle until the user provides some input.  If a timer is set for
+five seconds of idleness, it runs approximately five seconds after Emacs
+first becomes idle.  Even if @var{repeat} is address@hidden, this timer
+will not run again as long as Emacs remains idle, because the duration
+of idleness will continue to increase and will not go down to five
+seconds again.
+
+  Emacs can do various things while idle: garbage collect, autosave or
+handle data from a subprocess.  But these interludes during idleness do
+not interfere with idle timers, because they do not reset the clock of
+idleness to zero.  An idle timer set for 600 seconds will run when ten
+minutes have elapsed since the last user command was finished, even if
+subprocess output has been accepted thousands of times within those ten
+minutes, and even if there have been garbage collections and autosaves.
+
+  When the user supplies input, Emacs becomes non-idle while executing the
+input.  Then it becomes idle again, and all the idle timers that are
+set up to repeat will subsequently run another time, one by one.
+
address@hidden Emacs 19 feature
address@hidden current-idle-time
+This function returns the length of time Emacs has been idle, as a
+list of three integers: @code{(@var{high} @var{low} @var{microsec})}.
+The integers @var{high} and @var{low} combine to give the number of
+seconds of idleness, which is
address@hidden
address@hidden * 2**16 + @var{low}.
address@hidden ifnottex
address@hidden
+$high*2^{16}+low$.
address@hidden tex
+
+The third element, @var{microsec}, gives the microseconds since the
+start of the current second (or 0 for systems that return time with
+the resolution of only one second).
+
+The main use of this function is when an idle timer function wants to
+``take a break'' for a while.  It can set up another idle timer to
+call the same function again, after a few seconds more idleness.
+Here's an example:
+
address@hidden
+(defvar resume-timer nil
+  "Timer that `timer-function' used to reschedule itself, or nil.")
+
+(defun timer-function ()
+  ;; @r{If the user types a command while @code{resume-timer}}
+  ;; @r{is active, the next time this function is called from}
+  ;; @r{its main idle timer, deactivate @code{resume-timer}.}
+  (when resume-timer
+    (cancel-timer resume-timer))
+  address@hidden the work for a while}...
+  (when @var{taking-a-break}
+    (setq resume-timer
+          (run-with-idle-timer
+            ;; Compute an idle time @var{break-length}
+            ;; more than the current value.
+            (time-add (current-idle-time)
+                      (seconds-to-time @var{break-length}))
+            nil
+            'timer-function))))
address@hidden smallexample
address@hidden defun
+
+  Some idle timer functions in user Lisp packages have a loop that
+does a certain amount of processing each time around, and exits when
address@hidden(input-pending-p)} is address@hidden  That approach seems very
+natural but has two problems:
+
address@hidden
address@hidden
+It blocks out all process output (since Emacs accepts process output
+only while waiting).
+
address@hidden
+It blocks out any idle timers that ought to run during that time.
address@hidden itemize
+
address@hidden
+To avoid these problems, don't use that technique.  Instead, write
+such idle timers to reschedule themselves after a brief pause, using
+the method in the @code{timer-function} example above.
+
address@hidden Terminal Input
address@hidden Terminal Input
address@hidden terminal input
+
+  This section describes functions and variables for recording or
+manipulating terminal input.  See @ref{Display}, for related
+functions.
+
address@hidden
+* Input Modes::                Options for how input is processed.
+* Recording Input::    Saving histories of recent or all input events.
address@hidden menu
+
address@hidden Input Modes
address@hidden Input Modes
address@hidden input modes
address@hidden terminal input modes
+
address@hidden set-input-mode interrupt flow meta &optional quit-char
+This function sets the mode for reading keyboard input.  If
address@hidden is non-null, then Emacs uses input interrupts.  If it is
address@hidden, then it uses @sc{cbreak} mode.  The default setting is
+system-dependent.  Some systems always use @sc{cbreak} mode regardless
+of what is specified.
+
+When Emacs communicates directly with X, it ignores this argument and
+uses interrupts if that is the way it knows how to communicate.
+
+If @var{flow} is address@hidden, then Emacs uses @sc{xon/xoff}
+(@kbd{C-q}, @kbd{C-s}) flow control for output to the terminal.  This
+has no effect except in @sc{cbreak} mode.
+
address@hidden Emacs 19 feature
+The argument @var{meta} controls support for input character codes
+above 127.  If @var{meta} is @code{t}, Emacs converts characters with
+the 8th bit set into Meta characters.  If @var{meta} is @code{nil},
+Emacs disregards the 8th bit; this is necessary when the terminal uses
+it as a parity bit.  If @var{meta} is neither @code{t} nor @code{nil},
+Emacs uses all 8 bits of input unchanged.  This is good for terminals
+that use 8-bit character sets.
+
address@hidden Emacs 19 feature
+If @var{quit-char} is address@hidden, it specifies the character to
+use for quitting.  Normally this character is @kbd{C-g}.
address@hidden
address@hidden defun
+
+The @code{current-input-mode} function returns the input mode settings
+Emacs is currently using.
+
address@hidden Emacs 19 feature
address@hidden current-input-mode
+This function returns the current mode for reading keyboard input.  It
+returns a list, corresponding to the arguments of @code{set-input-mode},
+of the form @code{(@var{interrupt} @var{flow} @var{meta} @var{quit})} in
+which:
address@hidden @var
address@hidden interrupt
+is address@hidden when Emacs is using interrupt-driven input.  If
address@hidden, Emacs is using @sc{cbreak} mode.
address@hidden flow
+is address@hidden if Emacs uses @sc{xon/xoff} (@kbd{C-q}, @kbd{C-s})
+flow control for output to the terminal.  This value is meaningful only
+when @var{interrupt} is @code{nil}.
address@hidden meta
+is @code{t} if Emacs treats the eighth bit of input characters as
+the meta bit; @code{nil} means Emacs clears the eighth bit of every
+input character; any other value means Emacs uses all eight bits as the
+basic character code.
address@hidden quit
+is the character Emacs currently uses for quitting, usually @kbd{C-g}.
address@hidden table
address@hidden defun
+
address@hidden Recording Input
address@hidden Recording Input
address@hidden recording input
+
address@hidden recent-keys
+This function returns a vector containing the last 300 input events from
+the keyboard or mouse.  All input events are included, whether or not
+they were used as parts of key sequences.  Thus, you always get the last
+100 input events, not counting events generated by keyboard macros.
+(These are excluded because they are less interesting for debugging; it
+should be enough to see the events that invoked the macros.)
+
+A call to @code{clear-this-command-keys} (@pxref{Command Loop Info})
+causes this function to return an empty vector immediately afterward.
address@hidden defun
+
address@hidden Command open-dribble-file filename
address@hidden dribble file
+This function opens a @dfn{dribble file} named @var{filename}.  When a
+dribble file is open, each input event from the keyboard or mouse (but
+not those from keyboard macros) is written in that file.  A
+non-character event is expressed using its printed representation
+surrounded by @samp{<@dots{}>}.
+
+You close the dribble file by calling this function with an argument
+of @code{nil}.
+
+This function is normally used to record the input necessary to
+trigger an Emacs bug, for the sake of a bug report.
+
address@hidden
address@hidden
+(open-dribble-file "~/dribble")
+     @result{} nil
address@hidden group
address@hidden example
address@hidden deffn
+
+  See also the @code{open-termscript} function (@pxref{Terminal Output}).
+
address@hidden Terminal Output
address@hidden Terminal Output
address@hidden terminal output
+
+  The terminal output functions send output to a text terminal, or keep
+track of output sent to the terminal.  The variable @code{baud-rate}
+tells you what Emacs thinks is the output speed of the terminal.
+
address@hidden baud-rate
+This variable's value is the output speed of the terminal, as far as
+Emacs knows.  Setting this variable does not change the speed of actual
+data transmission, but the value is used for calculations such as
+padding.
+
+  It also affects decisions about whether to scroll part of the
+screen or repaint on text terminals.  @xref{Forcing Redisplay},
+for the corresponding functionality on graphical terminals.
+
+The value is measured in baud.
address@hidden defvar
+
+  If you are running across a network, and different parts of the
+network work at different baud rates, the value returned by Emacs may be
+different from the value used by your local terminal.  Some network
+protocols communicate the local terminal speed to the remote machine, so
+that Emacs and other programs can get the proper value, but others do
+not.  If Emacs has the wrong value, it makes decisions that are less
+than optimal.  To fix the problem, set @code{baud-rate}.
+
address@hidden baud-rate
+This obsolete function returns the value of the variable
address@hidden
address@hidden defun
+
address@hidden send-string-to-terminal string
+This function sends @var{string} to the terminal without alteration.
+Control characters in @var{string} have terminal-dependent effects.
+This function operates only on text terminals.
+
+One use of this function is to define function keys on terminals that
+have downloadable function key definitions.  For example, this is how (on
+certain terminals) to define function key 4 to move forward four
+characters (by transmitting the characters @kbd{C-u C-f} to the
+computer):
+
address@hidden
address@hidden
+(send-string-to-terminal "\eF4\^U\^F")
+     @result{} nil
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden Command open-termscript filename
address@hidden termscript file
+This function is used to open a @dfn{termscript file} that will record
+all the characters sent by Emacs to the terminal.  It returns
address@hidden  Termscript files are useful for investigating problems
+where Emacs garbles the screen, problems that are due to incorrect
+Termcap entries or to undesirable settings of terminal options more
+often than to actual Emacs bugs.  Once you are certain which characters
+were actually output, you can determine reliably whether they correspond
+to the Termcap specifications in use.
+
+You close the termscript file by calling this function with an
+argument of @code{nil}.
+
+See also @code{open-dribble-file} in @ref{Recording Input}.
+
address@hidden
address@hidden
+(open-termscript "../junk/termscript")
+     @result{} nil
address@hidden group
address@hidden example
address@hidden deffn
+
address@hidden Sound Output
address@hidden Sound Output
address@hidden sound
+
+  To play sound using Emacs, use the function @code{play-sound}.  Only
+certain systems are supported; if you call @code{play-sound} on a system
+which cannot really do the job, it gives an error.  Emacs version 20 and
+earlier did not support sound at all.
+
+  The sound must be stored as a file in RIFF-WAVE format (@samp{.wav})
+or Sun Audio format (@samp{.au}).
+
address@hidden play-sound sound
+This function plays a specified sound.  The argument, @var{sound}, has
+the form @code{(sound @var{properties}...)}, where the @var{properties}
+consist of alternating keywords (particular symbols recognized
+specially) and values corresponding to them.
+
+Here is a table of the keywords that are currently meaningful in
address@hidden, and their meanings:
+
address@hidden @code
address@hidden :file @var{file}
+This specifies the file containing the sound to play.
+If the file name is not absolute, it is expanded against
+the directory @code{data-directory}.
+
address@hidden :data @var{data}
+This specifies the sound to play without need to refer to a file.  The
+value, @var{data}, should be a string containing the same bytes as a
+sound file.  We recommend using a unibyte string.
+
address@hidden :volume @var{volume}
+This specifies how loud to play the sound.  It should be a number in the
+range of 0 to 1.  The default is to use whatever volume has been
+specified before.
+
address@hidden :device @var{device}
+This specifies the system device on which to play the sound, as a
+string.  The default device is system-dependent.
address@hidden table
+
+Before actually playing the sound, @code{play-sound}
+calls the functions in the list @code{play-sound-functions}.
+Each function is called with one argument, @var{sound}.
address@hidden defun
+
address@hidden play-sound-file file &optional volume device
+This function is an alternative interface to playing a sound @var{file}
+specifying an optional @var{volume} and @var{device}.
address@hidden defun
+
address@hidden play-sound-functions
+A list of functions to be called before playing a sound.  Each function
+is called with one argument, a property list that describes the sound.
address@hidden defvar
+
address@hidden X11 Keysyms
address@hidden Operating on X11 Keysyms
address@hidden X11 keysyms
+
+To define system-specific X11 keysyms, set the variable
address@hidden
+
address@hidden system-key-alist
+This variable's value should be an alist with one element for each
+system-specific keysym.  Each element has the form @code{(@var{code}
+. @var{symbol})}, where @var{code} is the numeric keysym code (not
+including the ``vendor specific'' bit,
address@hidden
+-2**28),
address@hidden ifnottex
address@hidden
+$-2^{28}$),
address@hidden tex
+and @var{symbol} is the name for the function key.
+
+For example @code{(168 . mute-acute)} defines a system-specific key (used
+by HP X servers) whose numeric code is
address@hidden
+-2**28
address@hidden ifnottex
address@hidden
+$-2^{28}$
address@hidden tex
++ 168.
+
+It is not crucial to exclude from the alist the keysyms of other X
+servers; those do no harm, as long as they don't conflict with the ones
+used by the X server actually in use.
+
+The variable is always local to the current terminal, and cannot be
+buffer-local.  @xref{Multiple Displays}.
address@hidden defvar
+
+You can specify which keysyms Emacs should use for the Meta, Alt, Hyper, and 
Super modifiers by setting these variables:
+
address@hidden x-alt-keysym
address@hidden x-meta-keysym
address@hidden x-hyper-keysym
address@hidden x-super-keysym
+The name of the keysym that should stand for the Alt modifier
+(respectively, for Meta, Hyper, and Super).  For example, here is
+how to swap the Meta and Alt modifiers within Emacs:
address@hidden
+(setq x-alt-keysym 'meta)
+(setq x-meta-keysym 'alt)
address@hidden lisp
address@hidden defvar
+
address@hidden Batch Mode
address@hidden Batch Mode
address@hidden batch mode
+
+  The command-line option @samp{-batch} causes Emacs to run
+noninteractively.  In this mode, Emacs does not read commands from the
+terminal, it does not alter the terminal modes, and it does not expect
+to be outputting to an erasable screen.  The idea is that you specify
+Lisp programs to run; when they are finished, Emacs should exit.  The
+way to specify the programs to run is with @samp{-l @var{file}}, which
+loads the library named @var{file}, or @samp{-f @var{function}}, which
+calls @var{function} with no arguments, or @samp{--eval @var{form}}.
+
+  Any Lisp program output that would normally go to the echo area,
+either using @code{message}, or using @code{prin1}, etc., with @code{t}
+as the stream, goes instead to Emacs's standard error descriptor when
+in batch mode.  Similarly, input that would normally come from the
+minibuffer is read from the standard input descriptor.
+Thus, Emacs behaves much like a noninteractive
+application program.  (The echo area output that Emacs itself normally
+generates, such as command echoing, is suppressed entirely.)
+
address@hidden noninteractive
+This variable is address@hidden when Emacs is running in batch mode.
address@hidden defvar
+
address@hidden Session Management
address@hidden Session Management
address@hidden session manager
+
+Emacs supports the X Session Management Protocol for suspension and
+restart of applications.  In the X Window System, a program called the
address@hidden manager} has the responsibility to keep track of the
+applications that are running.  During shutdown, the session manager
+asks applications to save their state, and delays the actual shutdown
+until they respond.  An application can also cancel the shutdown.
+
+When the session manager restarts a suspended session, it directs
+these applications to individually reload their saved state.  It does
+this by specifying a special command-line argument that says what
+saved session to restore.  For Emacs, this argument is @samp{--smid
address@hidden
+
address@hidden emacs-save-session-functions
+Emacs supports saving state by using a hook called
address@hidden  Each function in this hook is
+called when the session manager tells Emacs that the window system is
+shutting down.  The functions are called with no arguments and with the
+current buffer set to a temporary buffer.  Each function can use
address@hidden to add Lisp code to this buffer.  At the end, Emacs
+saves the buffer in a file that a subsequent Emacs invocation will
+load in order to restart the saved session.
+
+If a function in @code{emacs-save-session-functions} returns
address@hidden, Emacs tells the session manager to cancel the
+shutdown.
address@hidden defvar
+
+Here is an example that just inserts some text into @samp{*scratch*} when
+Emacs is restarted by the session manager.
+
address@hidden
address@hidden
+(add-hook 'emacs-save-session-functions 'save-yourself-test)
address@hidden group
+
address@hidden
+(defun save-yourself-test ()
+  (insert "(save-excursion
+  (switch-to-buffer \"*scratch*\")
+  (insert \"I am restored\"))")
+  nil)
address@hidden group
address@hidden example
+
address@hidden
+   arch-tag: 8378814a-30d7-467c-9615-74a80b9988a7
address@hidden ignore