* Time of Day:: Getting the current time.
* Time Conversion:: Converting a time from numeric form to a string, or
to calendrical data (or vice versa).
+* Time Calculations:: Adding, subtracting, comparing times, etc.
* Timers:: Setting a timer to call a function at a certain time.
* Terminal Input:: Recording terminal input for debugging.
* Terminal Output:: Recording terminal output for debugging.
* Sound Output:: Playing sounds on the computer's speaker.
-* Special Keysyms:: Defining system-specific key symbols for X windows.
+* X11 Keysyms:: Operating on key symbols for X Windows
* Flow Control:: How to turn output flow control on or off.
* Batch Mode:: Running Emacs without terminal interaction.
+* Session Management:: Saving and restoring state with X Session Management.
@end menu
@node Starting Up
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 Windows or MS Windows).
+a window system (X or MS Windows).
@defun suspend-emacs string
This function stops Emacs and returns control to the superior process.
HOME=/user/lewis
@end group
@end example
-@end defun
+@end deffn
@c Emacs 19 feature
@deffn Command setenv variable value
"HOME=/user/lewis")
@end group
@end 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.
@end defvar
@defvar path-separator
(see above) and from @code{file-attributes} (@pxref{File Attributes}).
@end defun
+@defun 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), and it also accepts the output of @code{current-time} and
+@code{file-attributes}.
+
+@emph{Warning}: Since the result is floating point, it may not be
+exact. Do not use this function if precise time stamps are required.
+@end defun
+
@node Time Conversion
@section Time Conversion
traditional Gregorian years do; for example, the year number @minus{}37
represents the Gregorian year 38 B.C@.
+@defun date-to-time string
+This function parses the time-string @var{string} and returns the
+corresponding time value.
+@end defun
+
@defun 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
string using that same coding system.
@end defun
+@defun 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}.
+@end defun
+
@defun decode-time time
This function converts a time value into calendrical information. The
return value is a list of nine elements, as follows:
if you try to encode a time that is out of range, an error results.
@end defun
+@node Time Calculations
+@section Time Calculations
+
+ These functions perform calendrical computations using time values
+(the kind of list that @code{current-time} returns).
+
+@defun time-less-p t1 t2
+This returns @code{t} if time value @var{t1} is less than time value
+@var{t2}.
+@end defun
+
+@defun 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.
+@end defun
+
+@defun 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:
+
+@example
+(time-add @var{time} (seconds-to-time @var{seconds}))
+@end example
+@end defun
+
+@defun time-to-days time
+This function returns the number of days between the beginning of year
+1 and @var{time}.
+@end defun
+
+@defun time-to-day-in-year time
+This returns the day number within the year corresponding to @var{time}.
+@end defun
+
+@defun date-leap-year-p year
+This function returns @code{t} if @var{year} is a leap year.
+@end defun
+
@node Timers
@section Timers for Delayed Execution
@cindex timer
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.
@end defun
@deffn Command open-dribble-file filename
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.
+
+@item :device @var{device}
+This specifies the system device on which to play the sound, as a
+string. The default device is system-dependent.
@end table
Before actually playing the sound, @code{play-sound}
Each function is called with one argument, @var{sound}.
@end defun
+@defun play-sound-file file &optional volume device
+@tindex play-sound-file
+This function is an alternative interface to playing a sound @var{file}
+specifying an optional @var{volume} and @var{device}.
+@end defun
+
@tindex play-sound-functions
@defvar 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.
@end defvar
-@node Special Keysyms
-@section System-Specific X11 Keysyms
+@node X11 Keysyms
+@section Operating on X11 Keysyms
To define system-specific X11 keysyms, set the variable
@code{system-key-alist}.
buffer-local. @xref{Multiple Displays}.
@end defvar
+You can specify which keysyms Emacs should use for the Meta, Alt, Hyper, and Super modifiers by setting these variables:
+
+@defvar x-alt-keysym
+@defvarx x-meta-keysym
+@defvarx x-hyper-keysym
+@defvarx 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:
+@lisp
+(setq x-alt-keysym 'meta)
+(setq x-meta-keysym 'alt)
+@end lisp
+@end defvar
+
@node Flow Control
@section Flow Control
@cindex flow control characters
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. Thus, Emacs behaves much like a noninteractive
+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.)
@defvar noninteractive
This variable is non-@code{nil} when Emacs is running in batch mode.
@end defvar
+
+@node Session Management
+@section Session Management
+@cindex session manager
+
+Emacs supports the X Session Management Protocol for suspension and
+restart of applications. In the X Window System, a program called the
+@dfn{session 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
+@var{session}}.
+
+@defvar emacs-save-session-functions
+@tindex emacs-save-session-functions
+Emacs supports saving state by using a hook called
+@code{emacs-save-session-functions}. 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 the current buffer set
+to a temporary buffer. Each functions can use @code{insert} to add
+Lisp code to this buffer. At the end, Emacs saves the buffer in a
+file that Emacs will load in order to restart the saved session.
+
+If a function in @code{emacs-save-session-functions} returns
+non-@code{nil}, Emacs tells the session manager to cancel the
+shutdown.
+@end defvar
+
+Here is an example that just inserts some text into *scratch* when
+Emacs is restarted by the session manager.
+
+@example
+@group
+(add-hook 'emacs-save-session-functions 'save-yourself-test)
+@end group
+
+@group
+(defun save-yourself-test ()
+ (insert "(save-excursion
+ (switch-to-buffer \"*scratch*\")
+ (insert \"I am restored\"))")
+ nil)
+@end group
+@end example
HCoop / bpt / emacs.git / blobdiff