@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999
+@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/os
-@node System Interface, Tips, Calendar, Top
+@node System Interface, Antinews, Calendar, Top
@chapter Operating System Interface
This chapter is about starting and getting out of Emacs, access to
pertaining to the terminal and the screen.
@menu
-* Starting Up:: Customizing Emacs start-up processing.
+* 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 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.
-* Special Keysyms:: Defining system-specific key symbols for X windows.
+* Sound Output:: Playing sounds on the computer's speaker.
+* 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
can customize these actions.
@menu
-* Start-up Summary:: Sequence of actions Emacs performs at start-up.
+* 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,
+* Command-Line Arguments:: How command-line arguments are processed,
and how you can customize them.
@end menu
-@node Start-up Summary
-@subsection Summary: Sequence of Actions at Start Up
+@node Startup Summary
+@subsection Summary: Sequence of Actions at Startup
@cindex initialization
-@cindex start up of Emacs
+@cindex startup of Emacs
@cindex @file{startup.el}
The order of operations performed (in @file{startup.el}) by Emacs when
@enumerate
@item
-It adds subdirectories to @code{load-path}, by running the file
-named @file{subdirs.el} in each directory that is listed.
+It adds subdirectories to @code{load-path}, by running the file named
+@file{subdirs.el} 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.
@item
It sets the language environment and the terminal coding system,
@cindex @file{site-start.el}
@item
-It loads the file @file{~/.emacs}, unless @samp{-q} or @samp{-batch} was
-specified on the command line. The @samp{-u} option can specify another
-user name whose home directory should be used instead of @file{~}.
+It loads your init file (usually @file{~/.emacs}), unless @samp{-q},
+@samp{-no-init-file}, 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{~}.
@item
It loads the library @file{default}, unless @code{inhibit-default-init}
It processes the action arguments from the command line.
@item
-It runs @code{term-setup-hook}.
+It runs @code{emacs-startup-hook} and then @code{term-setup-hook}.
@item
It calls @code{frame-notice-user-settings}, which modifies the
@item
It displays copyleft, nonwarranty, and basic use information, provided
-there were no remaining command line arguments (a few steps above),
+there were no remaining command-line arguments (a few steps above),
the value of @code{inhibit-startup-message} is @code{nil}, and the
buffer is still empty.
@end enumerate
@defopt 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 @file{.emacs} file:
+form to your init file:
@example
(setq inhibit-startup-echo-area-message
"@var{your-login-name}")
@end example
-Emacs explicitly checks for an expression as shown above in your
-@file{.emacs} file; your login name must appear in the expression as a
-Lisp string constant. Other methods of setting
+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
@code{inhibit-startup-echo-area-message} 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 @file{.emacs} file will not inhibit the
-message for someone else.
+but thoughtless copying of your init file will not inhibit the message
+for someone else.
@end defopt
@node Init File
-@subsection The Init File: @file{.emacs}
+@subsection The Init File, @file{.emacs}
@cindex init file
@cindex @file{.emacs}
- When you start Emacs, it normally attempts to load the file
-@file{.emacs} from your home directory. This file, if it exists, must
-contain Lisp code. It is called your @dfn{init file}. The command line
-switches @samp{-q} and @samp{-u} affect the use of the init file;
-@samp{-q} says not to load an init file, and @samp{-u} says to load a
-specified user's init file instead of yours. @xref{Entering Emacs,,,
-emacs, The GNU Emacs Manual}.
+ When you start Emacs, it normally attempts to load your @dfn{init
+file}, a file in your home directory. Its normal name is @file{.emacs},
+but you can alternatively call it @file{.emacs.el}, which enables you to
+byte-compile it (@pxref{Byte Compilation}); then the actual file loaded
+will be @file{.emacs.elc}.
+
+ The command-line switches @samp{-q} and @samp{-u} control whether and
+where to find the init file; @samp{-q} says not to load an init file,
+and @samp{-u @var{user}} says to load @var{user}'s init file instead of
+yours. @xref{Entering 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.
@cindex default init file
A site may have a @dfn{default init file}, which is the library named
loading of this file with the option @samp{-no-site-file}.
@defvar 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"}.
+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.
@end defvar
- If there is a great deal of code in your @file{.emacs} file, you
-should move it into another file named @file{@var{something}.el},
-byte-compile it (@pxref{Byte Compilation}), and make your @file{.emacs}
-file load the other file using @code{load} (@pxref{Loading}).
-
@xref{Init File Examples,,, emacs, The GNU Emacs Manual}, for
examples of how to make various commonly desired customizations in your
@file{.emacs} file.
@end defopt
@defvar before-init-hook
-This normal hook is run, once, just before loading of all the init files
+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.)
@end defvar
@defvar after-init-hook
-This normal hook is run, once, just after loading of all the init files
+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 the terminal-specific initialization.
+before loading the terminal-specific library and processing the
+command-line arguments.
+@end defvar
+
+@defvar emacs-startup-hook
+@tindex emacs-startup-hook
+This normal hook is run, once, just after handling the command line
+arguments, just before @code{term-setup-hook}.
+@end defvar
+
+@defvar user-init-file
+@tindex user-init-file
+This variable holds the 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.
@end defvar
@node Terminal-Specific
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. Normally, @code{term-file-prefix} has the value
+terminal type (specified by the environment variable @code{TERM}).
+Normally, @code{term-file-prefix} has the value
@code{"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.
@code{(getenv "TERM")} to find the full name of the terminal
type.@refill
- Your @file{.emacs} file can prevent the loading of the
+ Your init file can prevent the loading of the
terminal-specific library by setting the variable
@code{term-file-prefix} to @code{nil}. This feature is useful when
experimenting with your own peculiar customizations.
terminal-specific library by setting the variable
@code{term-setup-hook}. This is a normal hook which Emacs runs using
@code{run-hooks} at the end of Emacs initialization, after loading both
-your @file{.emacs} file and any terminal-specific libraries. You can
+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}.
@noindent
You may set the @code{term-file-prefix} variable to @code{nil} in your
-@file{.emacs} file if you do not wish to load the
+init file if you do not wish to load the
terminal-initialization file. To do this, put the following in
-your @file{.emacs} file: @code{(setq term-file-prefix nil)}.
+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.
@end defvar
@defvar term-setup-hook
This variable is a normal hook that Emacs runs after loading your
-@file{.emacs} file, the default initialization file (if any) and the
+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
See @code{window-setup-hook} in @ref{Window Systems}, for a related
feature.
-@node Command Line Arguments
-@subsection Command Line Arguments
-@cindex command line arguments
+@node Command-Line Arguments
+@subsection Command-Line Arguments
+@cindex command-line arguments
- You can use command line arguments to request various actions when you
+ 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
+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,
+ This section describes how Emacs processes command-line arguments,
and how you can customize them.
@ignore
(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
+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
@defun command-line
This function parses the command line that Emacs was called with,
-processes it, loads the user's @file{.emacs} file and displays the
+processes it, loads the user's init file and displays the
startup messages.
@end defun
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.
+to process its new command-line arguments.
@end defvar
@defvar command-switch-alist
@cindex switches on command line
@cindex options on command line
-@cindex command line options
+@cindex 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 of the
-form:
+A @dfn{command-line option} is an argument on the command line, which
+has the form:
@example
-@var{option}
(@var{option} . @var{handler-function})
@end example
-The @var{handler-function} is called to handle @var{option} and receives
-the option name as its sole argument.
+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
@code{command-line-args-left}. (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}
+The command-line arguments are parsed by the @code{command-line-1}
function in the @file{startup.el} file. See also @ref{Command
Switches, , Command Line Switches and Arguments, emacs, The GNU Emacs
Manual}.
@end defvar
@defvar command-line-args
-The value of this variable is the list of command line arguments passed
+The value of this variable is the list of command-line arguments passed
to Emacs.
@end defvar
@end defun
All the information in the Emacs process, aside from files that have
-been saved, is lost when the Emacs 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
+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
@code{save-buffers-kill-emacs}.
@defvar kill-emacs-query-functions
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.
+a window system (X or MS Windows).
@defun suspend-emacs string
This function stops Emacs and returns control to the superior process.
@end defun
@defvar suspend-hook
-This variable is a normal hook run before suspending.
+This variable is a normal hook that Emacs runs before suspending.
@end defvar
@defvar suspend-resume-hook
-This variable is a normal hook run after suspending.
+This variable is a normal hook that Emacs runs on resuming
+after a suspension.
@end defvar
@node System Environment
system Emacs is operating on. Here is a table of the possible values:
@table @code
+@item alpha-vms
+VMS on the Alpha.
+
@item aix-v3
AIX.
Silicon Graphics Irix system.
@item ms-dos
-Microsoft MS-DOS ``operating system.''
+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.
@item next-mach
NeXT Mach-based system.
VAX VMS.
@item windows-nt
-Microsoft 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.
@item xenix
SCO Xenix 386.
@end example
@end defun
-@vindex system-name
The symbol @code{system-name} is a variable as well as a function. In
fact, the function returns whatever value the variable
@code{system-name} currently holds. Thus, you can set the variable
Emacs was dumped. @xref{Building Emacs}.)
@end defvar
-@defun getenv var
+@deffn Command getenv var
@cindex environment variable access
This function returns the value of the environment variable @var{var},
as a string. Within Emacs, the environment variable values are kept in
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
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 Windows NT.
+and MS-Windows.
@end defvar
+@defun parse-colon-path path
+@tindex parse-colon-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}.
+
+@example
+(parse-colon-path ":/foo:/bar")
+ @result{} (nil "/foo/" "/bar/")
+@end example
+@end defun
+
@defvar 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.
@end defvar
@defun load-average &optional use-float
-This function returns the current 1-minute, 5-minute and 15-minute load
-averages in a list.
+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 non-@code{nil}, then they are returned
-as floating point numbers instead.
+as floating point numbers and without multiplying by 100.
@example
@group
@end defun
@defvar tty-erase-char
-@tindex tty-erase-char
This variable holds the erase character that was selected
in the system's terminal driver, before Emacs was started.
@end defvar
@defun setprv privilege-name &optional setp getprv
This function sets or resets a VMS privilege. (It does not exist on
-Unix.) The first arg 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 @code{nil}. The
-function returns @code{t} if successful, @code{nil} otherwise.
+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
+@code{nil}. The function returns @code{t} if successful, @code{nil}
+otherwise.
If the third argument, @var{getprv}, is non-@code{nil}, @code{setprv}
does not change the privilege, but returns @code{t} or @code{nil}
@defvar init-file-user
This variable says which user's init files should be used by Emacs---or
-@code{nil} if none. The value reflects command line options such as
+@code{nil} if none. The value reflects command-line options such as
@samp{-q} or @samp{-u @var{user}}.
Lisp packages that load files of customizations, or any other sort of
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 @file{~/.emacs} file if you do not
+variable to some other value in your init file if you do not
want to use the default value.
@end defvar
@defun user-full-name &optional uid
This function returns the full name of the logged-in user---or the value
-of the environment variables @code{NAME}, if that is set.
+of the environment variable @code{NAME}, if that is set.
+@c "Bil" is the correct spelling.
@example
@group
(user-full-name)
@end group
@end example
-If @var{uid} is non-@code{nil}, then it should be an integer, 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 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 non-@code{nil}, then it should be an integer (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}.
@end defun
@vindex user-full-name
This function returns the system's time value 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 since
-0:00 January 1, 1970, which is
-@ifinfo
+0:00 January 1, 1970 (local time), which is
+@ifnottex
@var{high} * 2**16 + @var{low}.
-@end ifinfo
+@end ifnottex
@tex
$high*2^{16}+low$.
@end tex
The third element, @var{microsec}, gives the microseconds since the
-start of the current second (or 0 for systems that return time only on
-the resolution of a second).
+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}. @xref{File Attributes}.
The value has the form @code{(@var{offset} @var{name})}. Here
@var{offset} 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
+second element, @var{name}, is a string giving the name of the time
zone. Both elements change when daylight savings 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.
(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 format-time-string format-string time
-This function converts @var{time} to a string according to
-@var{format-string}. The argument @var{format-string} may contain
-@samp{%}-sequences which say to substitute parts of the time. Here is a
-table of what the @samp{%}-sequences mean:
+@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
+@var{format-string} may contain @samp{%}-sequences which say to
+substitute parts of the time. Here is a table of what the
+@samp{%}-sequences mean:
@table @samp
@item %a
@item %H
This stands for the hour (00-23).
@item %I
-This stands for the hour (00-12).
+This stands for the hour (01-12).
@item %j
This stands for the day of the year (001-366).
@item %k
@item %R
This is a synonym for @samp{%H:%M}.
@item %S
-This stands for the seconds (00-60).
+This stands for the seconds (00-59).
@item %t
This stands for a tab character.
@item %T
@samp{%03S} 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
+@samp{%} 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
+@samp{%Ec}, @samp{%EC}, @samp{%Ex}, @samp{%EX}, @samp{%Ey}, and
+@samp{%EY}.
+
+@samp{O} 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 non-@code{nil}, 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} 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 @code{strftime}
+returns the resulting string, @code{format-time-string} decodes the
+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
Here is what the elements mean:
@table @var
-@item sec
+@item seconds
The number of seconds past the minute, as an integer between 0 and 59.
-@item minute
+@item minutes
The number of minutes past the hour, as an integer between 0 and 59.
@item hour
The hour of the day, as an integer between 0 and 23.
@var{dow} and @var{zone}.
@end defun
-@defun encode-time seconds minutes hour day month year &optional @dots{}zone
+@defun 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 treated just like other year numbers. If
-you want them to stand for years above 1900, you must alter them yourself
-before you call @code{encode-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 savings time rules. If specified, it can be either a list
@end example
You can perform simple date arithmetic by using out-of-range values for
-the @var{sec}, @var{minute}, @var{hour}, @var{day}, and @var{month}
+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.
@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
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
-@code{sit-for} or @code{read-char} which @emph{can} wait. Therefore, a
+@code{sit-for} 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.
later, and @var{args} are the arguments to give it when it is called.
The time @var{time} is specified as a string.
-Absolute times may be specified in a wide variety of formats, and tries
-to accept all common date formats. Valid formats include these two,
+Absolute times may be specified in a wide variety of formats; this
+function tries to accept all the commonly used date formats. Valid
+formats include these two,
@example
@var{year}-@var{month}-@var{day} @var{hour}:@var{min}:@var{sec} @var{timezone}
denotes exactly 103 months, 123 days, and 10862 seconds from now.
@end table
+For relative time values, Emacs considers a month to be exactly thirty
+days, and a year to be exactly 365.25 days.
+
If @var{time} is a number (integer or floating point), that specifies a
relative time measured in seconds.
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 became idle. Even if its @var{repeat} is true, 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.
+first becomes idle. Even if @var{repeat} is non-@code{nil}, 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
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, even if there have been garbage collections and autosaves.
+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
This function sets the mode for reading keyboard input. If
@var{interrupt} is non-null, then Emacs uses input interrupts. If it is
@code{nil}, then it uses @sc{cbreak} mode. The default setting is
-system dependent. Some systems always use @sc{cbreak} mode regardless
+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
@c Emacs 19 feature
@defun current-input-mode
-This function returns current mode for reading keyboard input. It
+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:
you reshuffle the keys on the keyboard without changing any command
bindings. Its value is normally a char-table, or else @code{nil}.
-If @code{keyboard-translate-table} is a char-table, then each character
-read from the keyboard is looked up in this character. If the value
-found there is non-@code{nil}, then it is used instead of the
-actual input character.
+If @code{keyboard-translate-table} is a char-table
+(@pxref{Char-Tables}), then each character read from the keyboard is
+looked up in this char-table. If the value found there is
+non-@code{nil}, then it is used instead of the actual input character.
In the example below, we set @code{keyboard-translate-table} to a
char-table. Then we fill it in to swap the characters @kbd{C-s} and
@kbd{C-\} and the characters @kbd{C-q} and @kbd{C-^}. Subsequently,
typing @kbd{C-\} has all the usual effects of typing @kbd{C-s}, and vice
-versa. (@xref{Flow Control} for more information on this subject.)
+versa. (@xref{Flow Control}, for more information on this subject.)
@cindex flow control example
@example
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
+@deffn Command open-dribble-file filename
@cindex 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
@section Terminal Output
@cindex terminal output
- The terminal output functions send output to the terminal or keep
+ The terminal output functions send output to the 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.
Control characters in @var{string} have terminal-dependent effects.
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
+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):
@end example
@end deffn
-@node Special Keysyms
-@section System-Specific X11 Keysyms
+@node Sound Output
+@section Sound Output
+@cindex 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}).
+
+@tindex play-sound
+@defun 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
+@var{sound}, and their meanings:
+
+@table @code
+@item :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}.
+
+@item :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.
+
+@item :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.
+
+@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}
+calls the functions in the list @code{play-sound-functions}.
+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 X11 Keysyms
+@section Operating on X11 Keysyms
To define system-specific X11 keysyms, set the variable
@code{system-key-alist}.
@defvar system-key-alist
This variable's value should be an alist with one element for each
-system-specific keysym. An element has this form: @code{(@var{code}
+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,
-@ifinfo
--2**28,
-@end ifinfo
+@ifnottex
+-2**28),
+@end ifnottex
@tex
-$-2^{28}$,
+$-2^{28}$),
@end 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
-@ifinfo
+For example @code{(168 . mute-acute)} defines a system-specific key (used
+by HP X servers) whose numeric code is
+@ifnottex
-2**28
-@end ifinfo
+@end ifnottex
@tex
$-2^{28}$
@end tex
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 X terminal and cannot be
+The variable is always local to the current terminal, and cannot be
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
@code{C-s} and @kbd{C-q} for flow control. Therefore, the choice of
@kbd{C-s} and @kbd{C-q} as command characters for searching and quoting
was natural and uncontroversial. With so many commands needing key
-assignments. of course we assigned meanings to nearly all @sc{ASCII}
+assignments, of course we assigned meanings to nearly all @sc{ascii}
control characters.
Later, some terminals were introduced which required these characters
@end deffn
You can use the function @code{enable-flow-control-on} in your
-@file{.emacs} file to enable flow control automatically on certain
+init file to enable flow control automatically on certain
terminal types.
@defun enable-flow-control-on &rest termtypes
@cindex batch mode
@cindex noninteractive use
- The command line option @samp{-batch} causes Emacs to run
+ 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
calls @var{function} with no arguments.
Any Lisp program output that would normally go to the echo area,
-either using @code{message} or using @code{prin1}, etc., with @code{t}
+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