@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2004
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001,
+@c 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/os
-@node System Interface, Antinews, Calendar, Top
+@node System Interface, Antinews, Display, Top
@chapter Operating System Interface
This chapter is about starting and getting out of Emacs, access to
* 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 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.
-* Terminal Input:: Recording terminal input for debugging.
-* Terminal Output:: Recording terminal output for debugging.
+* 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
-* 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 Startup Summary
@subsection Summary: Sequence of Actions at Startup
-@cindex initialization
+@cindex initialization of Emacs
@cindex startup of Emacs
@cindex @file{startup.el}
It runs the normal hook @code{before-init-hook}.
@item
-It loads the library @file{site-start}, unless the option
-@samp{-no-site-file} was specified. The library's file name is usually
-@file{site-start.el}.
+It loads the library @file{site-start} (if any), unless the option
+@samp{-Q} (or @samp{--no-site-file}) was specified. The library's file
+name is usually @file{site-start.el}.
@cindex @file{site-start.el}
@item
-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{~}.
+It loads your init file (usually @file{~/.emacs}), unless the option
+@samp{-q} (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{~}.
@item
-It loads the library @file{default}, unless @code{inhibit-default-init}
-is non-@code{nil}. (This is not done in @samp{-batch} mode or if
-@samp{-q} was specified on the command line.) The library's file name
-is usually @file{default.el}.
+It loads the library @file{default} (if any), unless
+@code{inhibit-default-init} is non-@code{nil}. (This is not done in
+@samp{-batch} mode, or if @samp{-Q} or @samp{-q} was specified on the
+command line.) The library's file name is usually @file{default.el}.
@cindex @file{default.el}
@item
@item
It displays copyleft, nonwarranty, and basic use information, provided
-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.
+the value of @code{inhibit-startup-message} is @code{nil}, you didn't
+specify @samp{--no-splash} or @samp{-Q}.
@end enumerate
@defopt inhibit-startup-message
@cindex @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 @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
+file}, a file in your home directory. Its normal name is
+@file{.emacs}, 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
+@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.
+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
-@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} is
-specified. But your own personal init file, if any, is loaded first; if
-it sets @code{inhibit-default-init} to a non-@code{nil} value, then
-Emacs does not subsequently load the @file{default.el} 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 non-@code{nil} value, then Emacs does not subsequently load the
+@file{default.el} 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}.
+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
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 arguments.
+command-line action 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
+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.
@end defvar
in the normal manner, by searching the @code{load-path} directories, and
trying the @samp{.elc} and @samp{.el} suffixes.
- 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 entry does not
-specify all the terminal's function keys. @xref{Terminal Input}.
-
@cindex Termcap
- When the name of the terminal type contains a hyphen, only the part of
-the name before the first hyphen is significant in choosing the library
-name. Thus, terminal types @samp{aaa-48} and @samp{aaa-30-rv} both use
-the @file{term/aaa} library. If necessary, the library can evaluate
-@code{(getenv "TERM")} to find the full name of the terminal
-type.@refill
+ 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.
+@xref{Terminal 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 type.@refill
Your init file can prevent the loading of the
terminal-specific library by setting the variable
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{Command
-Arguments, , Command Line Arguments, emacs, The GNU Emacs Manual}.
+function in the @file{startup.el} file. See also @ref{Emacs
+Invocation, , Command Line Arguments for Emacs Invocation, emacs, The
+GNU Emacs Manual}.
@end defvar
@defvar command-line-args
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}.
+@code{save-buffers-kill-emacs}, the higher level function from which
+@code{kill-emacs} is usually called.
@defvar 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
-@code{nil}, Emacs is not killed.
+@code{nil}, @code{save-buffers-kill-emacs} does not kill Emacs, and
+does not run the remaining functions in this hook. Calling
+@code{kill-emacs} directly does not run this hook.
@end defvar
@defvar kill-emacs-hook
This variable is a normal hook; once @code{save-buffers-kill-emacs} is
-finished with all file saving and confirmation, it runs the functions in
-this hook. This hook is not run in batch mode.
+finished with all file saving and confirmation, it calls
+@code{kill-emacs} which runs the functions in this hook.
+@code{kill-emacs} does not run this hook in batch mode.
+
+@code{kill-emacs} may be invoked directly (that is not via
+@code{save-buffers-kill-emacs}) 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
+@code{kill-emacs-query-functions}; if it needs to run regardless of
+how Emacs is killed, put it on @code{kill-emacs-hook}.
@end defvar
@node Suspending Emacs
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 or MS Windows).
+a window system (X, MS Windows, or Mac).
-@defun suspend-emacs string
+@defun 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.
(function (lambda ()
(or (y-or-n-p
"Really suspend? ")
- (error "Suspend cancelled")))))
+ (error "Suspend canceled")))))
@result{} (lambda nil
(or (y-or-n-p "Really suspend? ")
- (error "Suspend cancelled")))
+ (error "Suspend canceled")))
@end group
@group
(add-hook 'suspend-resume-hook
system, the user's @acronym{UID}, and so on.
@defvar system-configuration
-This variable holds the 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 @code{string-match}.
+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
+@code{string-match}.
@end defvar
+@cindex system type and name
@defvar 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:
@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
-the Lisp variable @code{process-environment}.
+as a string. @var{var} should be a string. If @var{var} is undefined
+in the environment, @code{getenv} returns @code{nil}. If returns
+@samp{""} if @var{var} is set but null. Within Emacs, the environment
+variable values are kept in the Lisp variable @code{process-environment}.
@example
@group
@end deffn
@c Emacs 19 feature
-@deffn Command setenv variable value
+@deffn Command setenv variable &optional value
This command sets the value of the environment variable named
-@var{variable} to @var{value}. Both arguments should be strings. This
-function works by modifying @code{process-environment}; binding that
-variable with @code{let} is also reasonable practice.
+@var{variable} to @var{value}. @var{variable} should be a string.
+Internally, Emacs Lisp can handle any string. However, normally
+@var{variable} 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
+@code{nil}, @code{setenv} removes @var{variable} from the environment.
+Otherwise, @var{value} should be a string.
+
+@code{setenv} works by modifying @code{process-environment}; binding
+that variable with @code{let} is also reasonable practice.
+
+@code{setenv} returns the new value of @var{variable}, or @code{nil}
+if it removed @var{variable} from the environment.
@end deffn
@defvar process-environment
@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
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.
+
@example
@group
(load-average)
@end defun
@defun emacs-pid
-This function returns the process @acronym{ID} of the Emacs process.
+This function returns the process @acronym{ID} of the Emacs process,
+as an integer.
@end defun
@defvar 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.
@end defvar
@defun setprv privilege-name &optional setp getprv
@code{nil}. The function returns @code{t} if successful, @code{nil}
otherwise.
- If the third argument, @var{getprv}, is non-@code{nil}, @code{setprv}
+If the third argument, @var{getprv}, is non-@code{nil}, @code{setprv}
does not change the privilege, but returns @code{t} or @code{nil}
indicating whether the privilege is currently enabled.
@end defun
@node User Identification
@section User Identification
+@cindex user identification
@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
+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
@samp{-q} or @samp{-u @var{user}}.
Lisp packages that load files of customizations, or any other sort of
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).
+to @var{uid} (which should be an integer), or @code{nil} if there is
+no such user.
@example
@group
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)
+If @var{uid} is non-@code{nil}, 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}.
instead of the current time. The argument should be a list whose first
two elements are integers. Thus, you can use times obtained from
@code{current-time} (see below) and from @code{file-attributes}
-(@pxref{File Attributes}).
+(@pxref{Definition of file-attributes}). @var{time-value} can also be
+a cons of two integers, but this is considered obsolete.
@example
@group
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 (local time), which is
+0:00 January 1, 1970 UTC (Coordinated Universal Time), which is
@ifnottex
@var{high} * 2**16 + @var{low}.
@end ifnottex
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}.
+get with the function @code{file-attributes}.
+@xref{Definition of file-attributes}.
@end defun
@c Emacs 19 feature
@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
-zone. Both elements change when daylight savings time begins or ends;
+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, both elements of the list are @code{nil}.
+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 be a cons cell
-containing two integers, or a list whose first two elements are
-integers. Thus, you can use times obtained from @code{current-time}
-(see above) and from @code{file-attributes} (@pxref{File Attributes}).
+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
+@code{file-attributes}. @xref{Definition of file-attributes}.
@end defun
@defun set-time-zone-rule tz
This function specifies the local time zone according to @var{tz}. If
@var{tz} 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.
+Universal Time. Otherwise, @var{tz} should be a string specifying a
+time zone rule.
@end defun
@defun float-time &optional time-value
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
+above). Thus, it accepts the output of @code{current-time} and
@code{file-attributes}.
@emph{Warning}: Since the result is floating point, it may not be
@section Time Conversion
These functions convert time values (lists of two or three integers)
-to strings or to calendrical information. There is also a function to
-convert calendrical information to a time value. You can get time
-values from the functions @code{current-time} (@pxref{Time of Day}) and
-@code{file-attributes} (@pxref{File Attributes}).
+to calendrical information and vice versa. You can get time values
+from the functions @code{current-time} (@pxref{Time of Day}) and
+@code{file-attributes} (@pxref{Definition of file-attributes}).
-Many operating systems are limited to time values that contain 32 bits
+ 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 @minus{}37
-represents the Gregorian year 38 B.C@.
+ 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
+@minus{}37 represents the Gregorian year 38 B.C@.
+
+@defun 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:
+
+@example
+(@var{seconds} @var{minutes} @var{hour} @var{day} @var{month} @var{year} @var{dow} @var{dst} @var{zone})
+@end example
+
+Here is what the elements mean:
+
+@table @var
+@item 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.
+@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.
+@item day
+The day of the month, as an integer between 1 and 31.
+@item month
+The month of the year, as an integer between 1 and 12.
+@item year
+The year, an integer typically greater than 1900.
+@item dow
+The day of week, as an integer between 0 and 6, where 0 stands for
+Sunday.
+@item dst
+@code{t} if daylight saving time is effect, otherwise @code{nil}.
+@item zone
+An integer indicating the time zone, as the number of seconds east of
+Greenwich.
+@end table
+
+@strong{Common Lisp Note:} Common Lisp has different meanings for
+@var{dow} and @var{zone}.
+@end defun
+
+@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 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
+@code{TZ} 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
+@code{decode-time} as the arguments to @code{encode-time}, like this:
+
+@example
+(apply 'encode-time (decode-time @dots{}))
+@end 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.
+@end defun
+
+@node Time Parsing
+@section Parsing and Formatting Times
+
+ These functions convert time values (lists of two or three integers)
+to text in a string, and vice versa.
@defun date-to-time string
This function parses the time-string @var{string} and returns the
@item %Y
This stands for the year with century.
@item %Z
-This stands for the time zone abbreviation.
+This stands for the time zone abbreviation (e.g., @samp{EST}).
+@item %z
+This stands for the time zone numerical offset (e.g., @samp{-0500}).
@end table
You can also specify the field width and type of padding for any of
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.
+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
+@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
the inverse conversion, use @code{float-time}.
@end defun
-@defun 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:
-
-@example
-(@var{seconds} @var{minutes} @var{hour} @var{day} @var{month} @var{year} @var{dow} @var{dst} @var{zone})
-@end example
-
-Here is what the elements mean:
-
-@table @var
-@item seconds
-The number of seconds past the minute, as an integer between 0 and 59.
-@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.
-@item day
-The day of the month, as an integer between 1 and 31.
-@item month
-The month of the year, as an integer between 1 and 12.
-@item year
-The year, an integer typically greater than 1900.
-@item dow
-The day of week, as an integer between 0 and 6, where 0 stands for
-Sunday.
-@item dst
-@code{t} if daylight savings time is effect, otherwise @code{nil}.
-@item zone
-An integer indicating the time zone, as the number of seconds east of
-Greenwich.
-@end table
-
-@strong{Common Lisp Note:} Common Lisp has different meanings for
-@var{dow} and @var{zone}.
-@end defun
-
-@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 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
-(as you would get from @code{current-time-zone}), a string as in the
-@code{TZ} environment variable, or an integer (as you would get from
-@code{decode-time}). The specified zone is used without any further
-alteration for daylight savings 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
-@code{decode-time} as the arguments to @code{encode-time}, like this:
+@node Processor Run Time
+@section Processor Run time
+@cindex processor run time
-@example
-(apply 'encode-time (decode-time @dots{}))
-@end example
+@defun 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
+@ifnottex
+@var{high} * 2**16 + @var{low}.
+@end ifnottex
+@tex
+$high*2^{16}+low$.
+@end tex
-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 third element, @var{microsec}, gives the microseconds (or 0 for
+systems that return time with the resolution of only one second).
-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.
+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.
@end defun
@node Time Calculations
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.
-
-@defun run-at-time time repeat function &rest args
-This function arranges to call @var{function} with arguments @var{args}
-at time @var{time}. The argument @var{function} is a function to call
-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; 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}
-
-@var{hour}:@var{min}:@var{sec} @var{timezone} @var{month}/@var{day}/@var{year}
-@end example
-
-@noindent
-where in both examples all fields are numbers; the format that
-@code{current-time-string} returns is also allowed, and many others
-as well.
-
-To specify a relative time, use numbers followed by units.
+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
+@code{with-local-quit}, 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}.
+
+@deffn 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
+@var{repeat} seconds after @var{time}. If @var{repeat} is @code{nil},
+the timer runs only once.
+
+@var{time} 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 @samp{@var{xxxx}},
+@samp{@var{x}:@var{xx}}, or @samp{@var{xx}:@var{xx}} (military time),
+and @samp{@var{xx}am}, @samp{@var{xx}AM}, @samp{@var{xx}pm},
+@samp{@var{xx}PM}, @samp{@var{xx}:@var{xx}am},
+@samp{@var{xx}:@var{xx}AM}, @samp{@var{xx}:@var{xx}pm}, or
+@samp{@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:
@table @samp
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.
-
-The argument @var{repeat} specifies how often to repeat the call. If
-@var{repeat} is @code{nil}, there are no repetitions; @var{function} is
-called just once, at @var{time}. If @var{repeat} is a number, it
-specifies a repetition period measured in seconds.
+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 place---@var{time} alone specifies that. There is one exception:
The function @code{run-at-time} returns a timer value that identifies
the particular scheduled future action. You can use this value to call
@code{cancel-timer} (see below).
-@end defun
+@end 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.
+
+@defvar 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.
+@end defvar
@defmac with-timeout (seconds timeout-forms@dots{}) body@dots{}
Execute @var{body}, but give up after @var{seconds} seconds. If
a timer to avoid waiting too long for an answer. @xref{Yes-or-No
Queries}.
-@defun run-with-idle-timer secs repeat function &rest args
+@defun 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
+@code{run-with-idle-timer}. 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.
+@end defun
+
+@node Idle Timers
+@section 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.
+
+@deffn 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.
+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
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} (see below).
-@end defun
+can use in calling @code{cancel-timer} (@pxref{Timers}).
+@end deffn
@cindex idleness
Emacs becomes ``idle'' when it starts waiting for user input, and it
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.
-@defun cancel-timer timer
-Cancel the requested action for @var{timer}, which should be a value
-previously returned by @code{run-at-time} or @code{run-with-idle-timer}.
-This cancels the effect of that call to @code{run-at-time}; the arrival
-of the specified time will not cause anything special to happen.
+@c Emacs 19 feature
+@defun current-idle-time
+If Emacs is idle, 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
+@ifnottex
+@var{high} * 2**16 + @var{low}.
+@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 with
+the resolution of only one second).
+
+When Emacs is not idle, @code{current-idle-time} returns @code{nil}.
+This is a convenient way to test whether Emacs is idle.
+
+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:
+
+@smallexample
+(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))
+ ...@var{do 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))))
+@end smallexample
@end 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
+@code{(input-pending-p)} is non-@code{nil}. That approach seems very
+natural but has two problems:
+
+@itemize
+@item
+It blocks out all process output (since Emacs accepts process output
+only while waiting).
+
+@item
+It blocks out any idle timers that ought to run during that time.
+@end itemize
+
+@noindent
+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.
+
@node Terminal Input
@section Terminal Input
@cindex terminal input
@menu
* Input Modes:: Options for how input is processed.
-* Translating Input:: Low level conversion of some characters or events
- into others.
* Recording Input:: Saving histories of recent or all input events.
@end menu
@cindex input modes
@cindex terminal input modes
-@defun set-input-mode interrupt flow meta quit-char
+@defun set-input-mode interrupt flow meta &optional quit-char
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
If @var{flow} is non-@code{nil}, 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. @xref{Flow Control}.
+has no effect except in @sc{cbreak} mode.
@c Emacs 19 feature
The argument @var{meta} controls support for input character codes
@end table
@end defun
-@node Translating Input
-@subsection Translating Input Events
-@cindex translating input events
-
- This section describes features for translating input events into
-other input events before they become part of key sequences. These
-features apply to each event in the order they are described here: each
-event is first modified according to @code{extra-keyboard-modifiers},
-then translated through @code{keyboard-translate-table} (if applicable),
-and finally decoded with the specified keyboard coding system. If it is
-being read as part of a key sequence, it is then added to the sequence
-being read; then subsequences containing it are checked first with
-@code{function-key-map} and then with @code{key-translation-map}.
-
-@c Emacs 19 feature
-@defvar extra-keyboard-modifiers
-This variable lets Lisp programs ``press'' the modifier keys on the
-keyboard. The value is a bit mask:
-
-@table @asis
-@item 1
-The @key{SHIFT} key.
-@item 2
-The @key{LOCK} key.
-@item 4
-The @key{CTL} key.
-@item 8
-The @key{META} key.
-@end table
-
-Each time the user types a keyboard key, it is altered as if the
-modifier keys specified in the bit mask were held down.
-
-When using a window system, the program can ``press'' any of the
-modifier keys in this way. Otherwise, only the @key{CTL} and @key{META}
-keys can be virtually pressed.
-@end defvar
-
-@defvar keyboard-translate-table
-This variable is the translate table for keyboard characters. It lets
-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
-(@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.)
-
-@cindex flow control example
-@example
-@group
-(defun evade-flow-control ()
- "Replace C-s with C-\ and C-q with C-^."
- (interactive)
-@end group
-@group
- (setq keyboard-translate-table
- (make-char-table 'keyboard-translate-table nil))
-@end group
-@group
- ;; @r{Swap @kbd{C-s} and @kbd{C-\}.}
- (aset keyboard-translate-table ?\034 ?\^s)
- (aset keyboard-translate-table ?\^s ?\034)
-@end group
-@group
- ;; @r{Swap @kbd{C-q} and @kbd{C-^}.}
- (aset keyboard-translate-table ?\036 ?\^q)
- (aset keyboard-translate-table ?\^q ?\036))
-@end group
-@end example
-
-Note that this translation is the first thing that happens to a
-character after it is read from the terminal. Record-keeping features
-such as @code{recent-keys} and dribble files record the characters after
-translation.
-@end defvar
-
-@defun keyboard-translate from to
-This function modifies @code{keyboard-translate-table} to translate
-character code @var{from} into character code @var{to}. It creates
-the keyboard translate table if necessary.
-@end defun
-
- The remaining translation features translate subsequences of key
-sequences being read. They are implemented in @code{read-key-sequence}
-and have no effect on input read with @code{read-event}.
-
-@defvar function-key-map
-This variable holds a keymap that describes the character sequences sent
-by function keys on an ordinary character terminal. This keymap has the
-same structure as other keymaps, but is used differently: it specifies
-translations to make while reading key sequences, rather than bindings
-for key sequences.
-
-If @code{function-key-map} ``binds'' a key sequence @var{k} to a vector
-@var{v}, then when @var{k} appears as a subsequence @emph{anywhere} in a
-key sequence, it is replaced with the events in @var{v}.
-
-For example, VT100 terminals send @kbd{@key{ESC} O P} when the
-keypad @key{PF1} key is pressed. Therefore, we want Emacs to translate
-that sequence of events into the single event @code{pf1}. We accomplish
-this by ``binding'' @kbd{@key{ESC} O P} to @code{[pf1]} in
-@code{function-key-map}, when using a VT100.
-
-Thus, typing @kbd{C-c @key{PF1}} sends the character sequence @kbd{C-c
-@key{ESC} O P}; later the function @code{read-key-sequence} translates
-this back into @kbd{C-c @key{PF1}}, which it returns as the vector
-@code{[?\C-c pf1]}.
-
-Entries in @code{function-key-map} are ignored if they conflict with
-bindings made in the minor mode, local, or global keymaps. The intent
-is that the character sequences that function keys send should not have
-command bindings in their own right---but if they do, the ordinary
-bindings take priority.
-
-The value of @code{function-key-map} is usually set up automatically
-according to the terminal's Terminfo or Termcap entry, but sometimes
-those need help from terminal-specific Lisp files. Emacs comes with
-terminal-specific files for many common terminals; their main purpose is
-to make entries in @code{function-key-map} beyond those that can be
-deduced from Termcap and Terminfo. @xref{Terminal-Specific}.
-@end defvar
-
-@defvar key-translation-map
-This variable is another keymap used just like @code{function-key-map}
-to translate input events into other events. It differs from
-@code{function-key-map} in two ways:
-
-@itemize @bullet
-@item
-@code{key-translation-map} goes to work after @code{function-key-map} is
-finished; it receives the results of translation by
-@code{function-key-map}.
-
-@item
-@code{key-translation-map} overrides actual key bindings. For example,
-if @kbd{C-x f} has a binding in @code{key-translation-map}, that
-translation takes effect even though @kbd{C-x f} also has a key binding
-in the global map.
-@end itemize
-
-The intent of @code{key-translation-map} is for users to map one
-character set to another, including ordinary characters normally bound
-to @code{self-insert-command}.
-@end defvar
-
-@cindex key translation function
-You can use @code{function-key-map} or @code{key-translation-map} for
-more than simple aliases, by using a function, instead of a key
-sequence, as the ``translation'' of a key. Then this function is called
-to compute the translation of that key.
-
-The key translation function receives one argument, which is the prompt
-that was specified in @code{read-key-sequence}---or @code{nil} if the
-key sequence is being read by the editor command loop. In most cases
-you can ignore the prompt value.
-
-If the function reads input itself, it can have the effect of altering
-the event that follows. For example, here's how to define @kbd{C-c h}
-to turn the character that follows into a Hyper character:
-
-@example
-@group
-(defun hyperify (prompt)
- (let ((e (read-event)))
- (vector (if (numberp e)
- (logior (lsh 1 24) e)
- (if (memq 'hyper (event-modifiers e))
- e
- (add-event-modifier "H-" e))))))
-
-(defun add-event-modifier (string e)
- (let ((symbol (if (symbolp e) e (car e))))
- (setq symbol (intern (concat string
- (symbol-name symbol))))
-@end group
-@group
- (if (symbolp e)
- symbol
- (cons symbol (cdr e)))))
-
-(define-key function-key-map "\C-ch" 'hyperify)
-@end group
-@end example
-
-Finally, if you have enabled keyboard character set decoding using
-@code{set-keyboard-coding-system}, decoding is done after the
-translations listed above. @xref{Specifying Coding Systems}. In future
-Emacs versions, character set decoding may be done before the other
-translations.
-
@node Recording Input
@subsection Recording Input
+@cindex recording input
@defun recent-keys
-This function returns a vector containing the last 100 input events from
+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.
@section Terminal Output
@cindex terminal output
- The terminal output functions send output to the terminal, or keep
+ 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.
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---even when using a window system. (We designed it
-this way despite the fact that a window system has no true ``output
-speed'', to give you a way to tune these decisions.)
+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.
@end defvar
@defun 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
were actually output, you can determine reliably whether they correspond
to the Termcap specifications in use.
-See also @code{open-dribble-file} in @ref{Terminal Input}.
+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}.
@example
@group
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}
@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.
@node X11 Keysyms
@section Operating on X11 Keysyms
+@cindex X11 keysyms
To define system-specific X11 keysyms, set the variable
@code{system-key-alist}.
@end lisp
@end defvar
-@node Flow Control
-@section Flow Control
-@cindex flow control characters
-
- This section attempts to answer the question ``Why does Emacs use
-flow-control characters in its command character set?'' For a second
-view on this issue, read the comments on flow control in the
-@file{emacs/INSTALL} file from the distribution; for help with Termcap
-entries and DEC terminal concentrators, see @file{emacs/etc/TERMS}.
-
-@cindex @kbd{C-s}
-@cindex @kbd{C-q}
- At one time, most terminals did not need flow control, and none used
-@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 @acronym{ASCII}
-control characters.
-
- Later, some terminals were introduced which required these characters
-for flow control. They were not very good terminals for full-screen
-editing, so Emacs maintainers ignored them. In later years, flow
-control with @kbd{C-s} and @kbd{C-q} became widespread among terminals,
-but by this time it was usually an option. And the majority of Emacs
-users, who can turn flow control off, did not want to switch to less
-mnemonic key bindings for the sake of flow control.
-
- So which usage is ``right''---Emacs's or that of some terminal and
-concentrator manufacturers? This question has no simple answer.
-
- One reason why we are reluctant to cater to the problems caused by
-@kbd{C-s} and @kbd{C-q} is that they are gratuitous. There are other
-techniques (albeit less common in practice) for flow control that
-preserve transparency of the character stream. Note also that their use
-for flow control is not an official standard. Interestingly, on the
-model 33 teletype with a paper tape punch (around 1970), @kbd{C-s} and
-@kbd{C-q} were sent by the computer to turn the punch on and off!
-
- As window systems and PC terminal emulators replace character-only
-terminals, the flow control problem is gradually disappearing. For the
-mean time, Emacs provides a convenient way of enabling flow control if
-you want it: call the function @code{enable-flow-control}.
-
-@deffn Command enable-flow-control
-This function enables use of @kbd{C-s} and @kbd{C-q} for output flow
-control, and provides the characters @kbd{C-\} and @kbd{C-^} as aliases
-for them using @code{keyboard-translate-table} (@pxref{Translating Input}).
-@end deffn
-
-You can use the function @code{enable-flow-control-on} in your
-init file to enable flow control automatically on certain
-terminal types.
-
-@defun enable-flow-control-on &rest termtypes
-This function enables flow control, and the aliases @kbd{C-\} and @kbd{C-^},
-if the terminal type is one of @var{termtypes}. For example:
-
-@smallexample
-(enable-flow-control-on "vt200" "vt300" "vt101" "vt131")
-@end smallexample
-@end defun
-
- Here is how @code{enable-flow-control} does its job:
-
-@enumerate
-@item
-@cindex @sc{cbreak}
-It sets @sc{cbreak} mode for terminal input, and tells the operating
-system to handle flow control, with @code{(set-input-mode nil t)}.
-
-@item
-It sets up @code{keyboard-translate-table} to translate @kbd{C-\} and
-@kbd{C-^} into @kbd{C-s} and @kbd{C-q}. Except at its very
-lowest level, Emacs never knows that the characters typed were anything
-but @kbd{C-s} and @kbd{C-q}, so you can in effect type them as @kbd{C-\}
-and @kbd{C-^} even when they are input for other commands.
-@xref{Translating Input}.
-@end enumerate
-
-If the terminal is the source of the flow control characters, then once
-you enable kernel flow control handling, you probably can make do with
-less padding than normal for that terminal. You can reduce the amount
-of padding by customizing the Termcap entry. You can also reduce it by
-setting @code{baud-rate} to a smaller value so that Emacs uses a smaller
-speed when calculating the padding needed. @xref{Terminal Output}.
-
@node Batch Mode
@section Batch Mode
@cindex batch mode
-@cindex noninteractive use
The command-line option @samp{-batch} causes Emacs to run
noninteractively. In this mode, Emacs does not read commands from the
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}, and @samp{-f @var{function}}, which
-calls @var{function} with no arguments.
+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}
@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 function can use @code{insert} to add
-Lisp code to this buffer. At the end, Emacs saves the buffer in a
-file that another Emacs will later load in order to restart the saved session.
+shutting down. The functions are called with no arguments and with the
+current buffer set to a temporary buffer. Each function can use
+@code{insert} 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
non-@code{nil}, Emacs tells the session manager to cancel the
HCoop / bpt / emacs.git / blobdiff