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This chapter is about starting and getting out of Emacs, access to values in the operating system environment, and terminal input, output, and flow control.
See section Building XEmacs, for related information. See also Emacs Display, for additional operating system status information pertaining to the terminal and the screen.
57.1 Starting Up XEmacs | Customizing XEmacs start-up processing. | |
57.2 Getting out of XEmacs | How exiting works (permanent or temporary). | |
57.3 Operating System Environment | Distinguish the name and kind of system. | |
57.4 User Identification | Finding the name and user id of the user. | |
57.5 Time of Day | Getting the current time. | |
57.6 Time Conversion | Converting a time from numeric form to a string, or to calendrical data (or vice versa). | |
57.7 Timers for Delayed Execution | Setting a timer to call a function at a certain time. | |
57.8 Terminal Input | Recording terminal input for debugging. | |
57.9 Terminal Output | Recording terminal output for debugging. | |
57.10 Flow Control | How to turn output flow control on or off. | |
57.11 Batch Mode | Running XEmacs without terminal interaction. |
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This section describes what XEmacs does when it is started, and how you can customize these actions.
57.1.1 Summary: Sequence of Actions at Start Up | Sequence of actions XEmacs performs at start-up. | |
57.1.2 The Init File: ‘.emacs’ | Details on reading the init file (‘.emacs’). | |
57.1.3 Terminal-Specific Initialization | How the terminal-specific Lisp file is read. | |
57.1.4 Command Line Arguments | How command line arguments are processed, and how you can customize them. |
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The order of operations performed (in ‘startup.el’) by XEmacs when it is started up is as follows:
before-init-hook
.
inhibit-default-init
is non-nil
. (This is not done in ‘-batch’ mode or if
‘-q’ was specified on the command line.) The library’s file name
is usually ‘default.el’.
after-init-hook
.
initial-major-mode
, provided
the buffer ‘*scratch*’ is still current and still in Fundamental
mode.
inhibit-startup-echo-area-message
.
term-setup-hook
.
frame-notice-user-settings
, which modifies the
parameters of the selected frame according to whatever the init files
specify.
window-setup-hook
. See section Terminal-Specific Initialization.
inhibit-startup-message
is nil
.
This variable inhibits the initial startup messages (the nonwarranty,
etc.). If it is non-nil
, then the messages are not printed.
This variable exists so you can set it in your personal init file, once you are familiar with the contents of the startup message. Do not set this variable in the init file of a new user, or in a way that affects more than one user, because that would prevent new users from receiving the information they are supposed to see.
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 ‘.emacs’ file:
(setq inhibit-startup-echo-area-message "your-login-name") |
Simply setting inhibit-startup-echo-area-message
to your login
name is not sufficient to inhibit the message; Emacs explicitly checks
whether ‘.emacs’ contains an expression as shown above. Your login
name must appear in the expression as a Lisp string constant.
This way, you can easily inhibit the message for yourself if you wish, but thoughtless copying of your ‘.emacs’ file will not inhibit the message for someone else.
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When you start XEmacs, it normally attempts to load the file ‘.emacs’ from your home directory. This file, if it exists, must contain Lisp code. It is called your init file. The command line switches ‘-q’ and ‘-u’ affect the use of the init file; ‘-q’ says not to load an init file, and ‘-u’ says to load a specified user’s init file instead of yours. See (xemacs)Entering XEmacs section ‘Entering XEmacs’ in The XEmacs User’s Manual.
A site may have a default init file, which is the library named
‘default.el’. XEmacs finds the ‘default.el’ file through the
standard search path for libraries (see section How Programs Do Loading).
The XEmacs 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 ‘-q’ is
specified. But your own personal init file, if any, is loaded first; if
it sets inhibit-default-init
to a non-nil
value, then
XEmacs does not subsequently load the ‘default.el’ file.
Another file for site-customization is ‘site-start.el’. Emacs loads this before the user’s init file. You can inhibit the loading of this file with the option ‘-no-site-file’.
This variable specifies the site-customization file to load
before the user’s init file. Its normal value is "site-start"
.
If there is a great deal of code in your ‘.emacs’ file, you
should move it into another file named ‘something.el’,
byte-compile it (see section Byte Compilation), and make your ‘.emacs’
file load the other file using load
(see section Loading).
See (xemacs)Init File Examples section ‘Init File Examples’ in The XEmacs User’s Manual, for examples of how to make various commonly desired customizations in your ‘.emacs’ file.
This variable prevents XEmacs from loading the default initialization
library file for your session of XEmacs. If its value is non-nil
,
then the default library is not loaded. The default value is
nil
.
These two normal hooks are run just before, and just after, loading of the user’s init file, ‘default.el’, and/or ‘site-start.el’.
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Each terminal type can have its own Lisp library that XEmacs loads when
run on that type of terminal. For a terminal type named termtype,
the library is called ‘term/termtype’. XEmacs finds the file
by searching the load-path
directories as it does for other
files, and trying the ‘.elc’ and ‘.el’ suffixes. Normally,
terminal-specific Lisp library is located in ‘emacs/lisp/term’, a
subdirectory of the ‘emacs/lisp’ directory in which most XEmacs Lisp
libraries are kept.
The library’s name is constructed by concatenating the value of the
variable term-file-prefix
and the terminal type. Normally,
term-file-prefix
has the value "term/"
; changing this
is not recommended.
The usual function of a terminal-specific library is to enable special
keys to send sequences that XEmacs can recognize. It may also need to
set or add to function-key-map
if the Termcap entry does not
specify all the terminal’s function keys. See section Terminal Input.
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 ‘aaa-48’ and ‘aaa-30-rv’ both use
the ‘term/aaa’ library. If necessary, the library can evaluate
(getenv "TERM")
to find the full name of the terminal
type.
Your ‘.emacs’ file can prevent the loading of the
terminal-specific library by setting the variable
term-file-prefix
to nil
. This feature is useful when
experimenting with your own peculiar customizations.
You can also arrange to override some of the actions of the
terminal-specific library by setting the variable
term-setup-hook
. This is a normal hook which XEmacs runs using
run-hooks
at the end of XEmacs initialization, after loading both
your ‘.emacs’ file and any terminal-specific libraries. You can
use this variable to define initializations for terminals that do not
have their own libraries. See section Hooks.
If the term-file-prefix
variable is non-nil
, XEmacs loads
a terminal-specific initialization file as follows:
(load (concat term-file-prefix (getenv "TERM"))) |
You may set the term-file-prefix
variable to nil
in your
‘.emacs’ file if you do not wish to load the
terminal-initialization file. To do this, put the following in
your ‘.emacs’ file: (setq term-file-prefix nil)
.
This variable is a normal hook that XEmacs runs after loading your ‘.emacs’ file, the default initialization file (if any) and the terminal-specific Lisp file.
You can use term-setup-hook
to override the definitions made by a
terminal-specific file.
This variable is a normal hook which XEmacs runs after loading your
‘.emacs’ file and the default initialization file (if any), after
loading terminal-specific Lisp code, and after running the hook
term-setup-hook
.
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You can use command line arguments to request various actions when you start XEmacs. Since you do not need to start XEmacs more than once per day, and will often leave your XEmacs session running longer than that, command line arguments are hardly ever used. As a practical matter, it is best to avoid making the habit of using them, since this habit would encourage you to kill and restart XEmacs unnecessarily often. These options exist for two reasons: to be compatible with other editors (for invocation by other programs) and to enable shell scripts to run specific Lisp programs.
This section describes how Emacs processes command line arguments, and how you can customize them.
This function parses the command line that XEmacs was called with, processes it, loads the user’s ‘.emacs’ file and displays the startup messages.
The value of this variable is t
once the command line has been
processed.
If you redump XEmacs by calling dump-emacs
, you may wish to set
this variable to nil
first in order to cause the new dumped XEmacs
to process its new command line arguments.
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 command line option is an argument on the command line of the form:
-option |
The elements of the command-switch-alist
look like this:
(option . handler-function) |
The handler-function is called to handle 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 handler-function can find all the
remaining command-line arguments in the variable
command-line-args-left
. (The entire list of command-line
arguments is in command-line-args
.)
The command line arguments are parsed by the command-line-1
function in the ‘startup.el’ file. See also (xemacs)Command Switches section ‘Command Line Switches and Arguments’ in The XEmacs User’s Manual.
The value of this variable is the list of command line arguments passed to XEmacs.
This variable’s value is a list of functions for handling an
unrecognized command-line argument. Each time the next argument to be
processed has no special meaning, the functions in this list are called,
in order of appearance, until one of them returns a non-nil
value.
These functions are called with no arguments. They can access the
command-line argument under consideration through the variable
argi
. The remaining arguments (not including the current one)
are in the variable command-line-args-left
.
When a function recognizes and processes the argument in argi
, it
should return a non-nil
value to say it has dealt with that
argument. If it has also dealt with some of the following arguments, it
can indicate that by deleting them from command-line-args-left
.
If all of these functions return nil
, then the argument is used
as a file name to visit.
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There are two ways to get out of XEmacs: you can kill the XEmacs job, which exits permanently, or you can suspend it, which permits you to reenter the XEmacs process later. As a practical matter, you seldom kill XEmacs—only when you are about to log out. Suspending is much more common.
57.2.1 Killing XEmacs | Exiting XEmacs irreversibly. | |
57.2.2 Suspending XEmacs | Exiting XEmacs reversibly. |
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Killing XEmacs means ending the execution of the XEmacs process. The
parent process normally resumes control. The low-level primitive for
killing XEmacs is kill-emacs
.
This function exits the XEmacs process and kills it.
If exit-data is a fixnum, then it is used as the exit status of the XEmacs process. (This is useful primarily in batch operation; see Batch Mode.)
If exit-data is a string, its contents are stuffed into the terminal input buffer so that the shell (or whatever program next reads input) can read them.
All the information in the XEmacs process, aside from files that have
been saved, is lost when the XEmacs is killed. Because killing XEmacs
inadvertently can lose a lot of work, XEmacs queries for confirmation
before actually terminating if you have buffers that need saving or
subprocesses that are running. This is done in the function
save-buffers-kill-emacs
.
After asking the standard questions, save-buffers-kill-emacs
calls the functions in the list kill-buffer-query-functions
, in
order of appearance, with no arguments. These functions can ask for
additional confirmation from the user. If any of them returns
non-nil
, XEmacs is not killed.
This variable is a normal hook; once save-buffers-kill-emacs
is
finished with all file saving and confirmation, it runs the functions in
this hook.
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Suspending XEmacs means stopping XEmacs temporarily and returning
control to its superior process, which is usually the shell. This
allows you to resume editing later in the same XEmacs process, with the
same buffers, the same kill ring, the same undo history, and so on. To
resume XEmacs, use the appropriate command in the parent shell—most
likely fg
.
Some operating systems do not support suspension of jobs; on these systems, “suspension” actually creates a new shell temporarily as a subprocess of XEmacs. Then you would exit the shell to return to XEmacs.
Suspension is not useful with window systems such as X, because the XEmacs job may not have a parent that can resume it again, and in any case you can give input to some other job such as a shell merely by moving to a different window. Therefore, suspending is not allowed when XEmacs is an X client.
This function stops XEmacs and returns control to the superior process.
If and when the superior process resumes XEmacs, suspend-emacs
returns nil
to its caller in Lisp.
If optional arg stuffstring is non-nil
, its characters are
sent to be read as terminal input by XEmacs’s superior shell. The
characters in stuffstring are not echoed by the superior shell;
only the results appear.
Before suspending, suspend-emacs
runs the normal hook
suspend-hook
. In Emacs version 18, suspend-hook
was not a
normal hook; its value was a single function, and if its value was
non-nil
, then suspend-emacs
returned immediately without
actually suspending anything.
After the user resumes XEmacs, suspend-emacs
runs the normal hook
suspend-resume-hook
. See section Hooks.
The next redisplay after resumption will redraw the entire screen,
unless the variable no-redraw-on-reenter
is non-nil
(see section Refreshing the Screen).
In the following example, note that ‘pwd’ is not echoed after XEmacs is suspended. But it is read and executed by the shell.
(suspend-emacs) ⇒ nil (add-hook 'suspend-hook (function (lambda () (or (y-or-n-p "Really suspend? ") (error "Suspend cancelled"))))) ⇒ (lambda nil (or (y-or-n-p "Really suspend? ") (error "Suspend cancelled"))) (add-hook 'suspend-resume-hook (function (lambda () (message "Resumed!")))) ⇒ (lambda nil (message "Resumed!")) (suspend-emacs "pwd") ⇒ nil ---------- Buffer: Minibuffer ---------- Really suspend? y ---------- Buffer: Minibuffer ---------- ---------- Parent Shell ---------- lewis@slug[23] % /user/lewis/manual lewis@slug[24] % fg ---------- Echo Area ---------- Resumed! |
This variable is a normal hook run before suspending.
This variable is a normal hook run after suspending.
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XEmacs provides access to variables in the operating system environment through various functions. These variables include the name of the system, the user’s UID, and so on.
The value of this variable is a symbol indicating the type of operating system XEmacs is operating on. Here is a table of the possible values:
aix
AIX 4.2 or later.
berkeley-unix
Berkeley BSD.
cygwin32
Cygwin.
darwin
Mac OS X.
gnu
A GNU system using the GNU HURD and Mach.
hpux
Hewlett-Packard HPUX operating system, version 11.0 or later.
irix
Silicon Graphics Irix system, version 6.0 or later.
linux
A GNU system using the Linux kernel.
mach
The Mach kernel with a BSD 4.3 layer.
usg-unix-v
AT&T System V.
windows-nt
Microsoft windows NT or one of its descendants.
We do not wish to add new symbols to make finer distinctions unless it
is absolutely necessary! In fact, we hope to eliminate some of these
alternatives in the future. We recommend using
system-configuration
to distinguish between different operating
systems.
This variable holds the three-part configuration name for the
hardware/software configuration of your system, as a string. The
convenient way to test parts of this string is with string-match
.
This function returns the name of the machine you are running on.
(system-name) ⇒ "prep.ai.mit.edu" |
The symbol system-name
is a variable as well as a function. In
fact, the function returns whatever value the variable
system-name
currently holds. Thus, you can set the variable
system-name
in case Emacs is confused about the name of your
system. The variable is also useful for constructing frame titles
(see section Frame Titles).
If this variable is non-nil
, it is used instead of
system-name
for purposes of generating email addresses. For
example, it is used when constructing the default value of
user-mail-address
. See section User Identification. (Since this is
done when XEmacs starts up, the value actually used is the one saved when
XEmacs was dumped. See section Building XEmacs.)
This function returns the value of the environment variable var,
as a string. Within XEmacs, the environment variable values are kept in
the Lisp variable process-environment
.
When invoked interactively, getenv
prints the value in the echo area.
(getenv "USER") ⇒ "lewis" lewis@slug[10] % printenv PATH=.:/user/lewis/bin:/usr/bin:/usr/local/bin USER=lewis TERM=ibmapa16 SHELL=/bin/csh HOME=/user/lewis |
This command sets the value of the environment variable named
variable to value. Both arguments should be strings. This
function works by modifying process-environment
; binding that
variable with let
is also reasonable practice.
This variable is a list of strings, each describing one environment
variable. The functions getenv
and setenv
work by
manipulating this variable.
process-environment ⇒ ("l=/usr/stanford/lib/gnuemacs/lisp" "PATH=.:/user/lewis/bin:/usr/class:/nfsusr/local/bin" "USER=lewis" "TERM=ibmapa16" "SHELL=/bin/csh" "HOME=/user/lewis") |
This variable holds a string which says which character separates
directories in a search path (as found in an environment variable). Its
value is ":"
for Unix and GNU systems, and ";"
for MS-DOS
and Windows NT.
This variable holds the program name under which Emacs was invoked. The value is a string, and does not include a directory name.
This variable holds the directory from which the Emacs executable was
invoked, or perhaps nil
if that directory cannot be determined.
If non-nil
, this is a directory within which to look for the
‘lib-src’ and ‘etc’ subdirectories. This is non-nil
when Emacs can’t find those directories in their standard installed
locations, but can find them in a directory related somehow to the one
containing the Emacs executable.
This function returns a list of the current 1-minute, 5-minute and 15-minute load averages. The values are integers that are 100 times the system load averages. (The load averages indicate the number of processes trying to run.)
When use-floats is non-nil
, floats will be returned instead
of integers. These floats are not multiplied by 100.
(load-average) ⇒ (169 158 164) (load-average t) ⇒ (1.69921875 1.58984375 1.640625) lewis@rocky[5] % uptime 8:06pm up 16 day(s), 21:57, 40 users, load average: 1.68, 1.59, 1.64 |
If the 5-minute or 15-minute load averages are not available, return a shortened list, containing only those averages which are available.
On some systems, this function may require special privileges to run, or it may be unimplemented for the particular system type. In that case, the function will signal an error.
This function returns the process ID of the Emacs process.
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This holds the nominal email address of the user who is using Emacs. When Emacs starts up, it computes a default value that is usually right, but users often set this themselves when the default value is not right.
If you don’t specify uid, this function returns the name under
which the user is logged in. If the environment variable LOGNAME
is set, that value is used. Otherwise, if the environment variable
USER
is set, that value is used. Otherwise, the value is based
on the effective UID, not the real UID.
If you specify uid, the value is the user name that corresponds to uid (which should be a fixnum).
(user-login-name) ⇒ "lewis" |
This function returns the user name corresponding to Emacs’s real
UID. This ignores the effective UID and ignores the
environment variables LOGNAME
and USER
.
This variable holds the name of the user running this Emacs. It is
initialized at startup time from the value of NAME
environment
variable. You can change the value of this variable to alter the result
of the user-full-name
function.
This function returns the full name of user. If user is
nil
, it defaults to the user running this Emacs. In that case,
the value of user-full-name
variable, if non-nil
, will be
used.
If user is specified explicitly, user-full-name
variable is
ignored.
(user-full-name) ⇒ "Hrvoje Niksic" (setq user-full-name "Hrvoje \"Niksa\" Niksic") (user-full-name) ⇒ "Hrvoje \"Niksa\" Niksic" (user-full-name "hniksic") ⇒ "Hrvoje Niksic" |
The symbols user-login-name
, user-real-login-name
and
user-full-name
are variables as well as functions. The functions
return the same values that the variables hold. These variables allow
you to “fake out” Emacs by telling the functions what to return. The
variables are also useful for constructing frame titles (see section Frame Titles).
This function returns the real UID of the user.
(user-real-uid) ⇒ 19 |
This function returns the effective UID of the user.
This function returns the “HOME
” directory of the user, and is
intended to replace occurrences of “(getenv "HOME")
”. Under
Unix systems, the following is done:
(getenv "HOME")
”, if set.
HOME
directory via
getpwent()
, but this has not yet been implemented.)
Under MS Windows, this is done:
(getenv "HOME")
”, if set.
HOMEDRIVE
and HOMEPATH
are
both set, return the concatenation (the following description uses MS
Windows environment variable substitution syntax):
%HOMEDRIVE%%HOMEPATH%
.
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This section explains how to determine the current time and the time zone.
This function returns the current time and date as a humanly-readable
string. The format of the string is unvarying; the number of characters
used for each part is always the same, so you can reliably use
substring
to extract pieces of it. It is wise to count the
characters from the beginning of the string rather than from the end, as
additional information may be added at the end.
The argument time-value, if given, specifies a time to format
instead of the current time. The argument should be a list whose first
two elements are fixnums. Thus, you can use times obtained from
current-time
(see below) and from file-attributes
(see section Other Information about Files).
(current-time-string) ⇒ "Wed Oct 14 22:21:05 1987" |
This function returns the system’s time value as a list of three
integers: (high low microsec)
. The integers
high and low combine to give the number of seconds since
0:00 January 1, 1970, which is
The third element, 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).
The first two elements can be compared with file time values such as you
get with the function file-attributes
. See section Other Information about Files.
This function returns a list describing the time zone that the user is in.
The value has the form (offset name)
. Here
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, 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.
If the operating system doesn’t supply all the information necessary to
compute the value, both elements of the list are nil
.
The argument time-value, if given, specifies a time to analyze
instead of the current time. The argument should be a cons cell
containing two fixnums, or a list whose first two elements are
fixnums. Thus, you can use times obtained from current-time
(see above) and from file-attributes
(see section Other Information about Files).
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These functions convert time values (lists of two or three fixnums)
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 current-time
(see section Time of Day) and
file-attributes
(see section Other Information about Files).
This function converts time to a string according to format-string. If time is omitted, it defaults to the current time. The argument format-string may contain ‘%’-sequences which say to substitute parts of the time. Here is a table of what the ‘%’-sequences mean:
This stands for the abbreviated name of the day of week.
This stands for the full name of the day of week.
This stands for the abbreviated name of the month.
This stands for the full name of the month.
This is a synonym for ‘%x %X’.
This has a locale-specific meaning. In the default locale (named C), it is equivalent to ‘%A, %B %e, %Y’.
This stands for the day of month, zero-padded.
This is a synonym for ‘%m/%d/%y’.
This stands for the day of month, blank-padded.
This is a synonym for ‘%b’.
This stands for the hour (00-23).
This stands for the hour (00-12).
This stands for the day of the year (001-366).
This stands for the hour (0-23), blank padded.
This stands for the hour (1-12), blank padded.
This stands for the month (01-12).
This stands for the minute (00-59).
This stands for a newline.
This stands for ‘AM’ or ‘PM’, as appropriate.
This is a synonym for ‘%I:%M:%S %p’.
This is a synonym for ‘%H:%M’.
This stands for the seconds (00-60).
This stands for a tab character.
This is a synonym for ‘%H:%M:%S’.
This stands for the week of the year (01-52), assuming that weeks start on Sunday.
This stands for the numeric day of week (0-6). Sunday is day 0.
This stands for the week of the year (01-52), assuming that weeks start on Monday.
This has a locale-specific meaning. In the default locale (named C), it is equivalent to ‘%D’.
This has a locale-specific meaning. In the default locale (named C), it is equivalent to ‘%T’.
This stands for the year without century (00-99).
This stands for the year with century.
This stands for the time zone abbreviation.
This stands for the month as a lowercase Roman number (i-xii)
This stands for the month as an uppercase Roman number (I-XII)
This function converts a time value into calendrical information. The
optional specified-time should be a list of
(high low . ignored) or (high . low), as from
current-time
and file-attributes
, or nil
to use the
current time.
The return value is a list of nine elements, as follows:
(seconds minutes hour day month year dow dst zone) |
Here is what the elements mean:
The number of seconds past the minute, as an integer between 0 and 59.
The number of minutes past the hour, as an integer between 0 and 59.
The hour of the day, as an integer between 0 and 23.
The day of the month, as an integer between 1 and 31.
The month of the year, as an integer between 1 and 12.
The year, an integer typically greater than 1900.
The day of week, as an integer between 0 and 6, where 0 stands for Sunday.
t
if daylight savings time is effect, otherwise nil
.
An integer indicating the time zone, as the number of seconds east of Greenwich.
Note that Common Lisp has different meanings for dow and zone.
This function is the inverse of decode-time
. It converts seven
items of calendrical data into a time value. For the meanings of the
arguments, see the table above under 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 encode-time
.
The optional argument 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 current-time-zone
) or an integer (as you
would get from decode-time
). The specified zone is used without
any further alteration for daylight savings time.
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You can set up a timer to call a function at a specified future time.
This function adds a timeout, to be signaled after the timeout period
has elapsed. secs is a number of seconds, expressed as an integer
or a float. function will be called after that many seconds have
elapsed, with one argument, the given object. If the optional
resignal argument is provided, then after this timeout expires,
add-timeout
will automatically be called again with
resignal as the first argument.
This function returns an object which is the id of this particular
timeout. You can pass that object to disable-timeout
to turn off
the timeout before it has been signalled.
The number of seconds may be expressed as a floating-point number, in which case some fractional part of a second will be used. Caveat: the usable timeout granularity will vary from system to system.
Adding a timeout causes a timeout event to be returned by
next-event
, and the function will be invoked by
dispatch-event
, so if XEmacs is in a tight loop, the function will
not be invoked until the next call to sit-for or until the return to
top-level (the same is true of process filters).
WARNING: if you are thinking of calling add-timeout from inside of a callback function as a way of resignalling a timeout, think again. There is a race condition. That’s why the resignal argument exists.
(NOTE: In FSF Emacs, this function is called run-at-time
and
has different semantics.)
Cancel the requested action for id, which should be a value
previously returned by add-timeout
. This cancels the effect of
that call to add-timeout
; the arrival of the specified time will
not cause anything special to happen.
(NOTE: In FSF Emacs, this function is called cancel-timer
.)
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This section describes functions and variables for recording or manipulating terminal input. See Emacs Display, for related functions.
57.8.1 Input Modes | Options for how input is processed. | |
57.8.2 Translating Input Events | Low level conversion of some characters or events into others. | |
57.8.3 Recording Input | Saving histories of recent or all input events. |
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This function sets the mode for reading keyboard input. If
interrupt is non-null, then XEmacs uses input interrupts. If it is
nil
, then it uses CBREAK mode. When XEmacs communicates
directly with X, it ignores this argument and uses interrupts if that is
the way it knows how to communicate.
If flow is non-nil
, then XEmacs uses XON/XOFF (C-q,
C-s) flow control for output to the terminal. This has no effect except
in CBREAK mode. See section Flow Control.
The default setting is system dependent. Some systems always use CBREAK mode regardless of what is specified.
The argument meta controls support for input character codes
above 127. If meta is t
, XEmacs converts characters with
the 8th bit set into Meta characters. If meta is nil
,
XEmacs disregards the 8th bit; this is necessary when the terminal uses
it as a parity bit. If meta is neither t
nor nil
,
XEmacs uses all 8 bits of input unchanged. This is good for terminals
using European 8-bit character sets.
If quit-char is non-nil
, it specifies the character to
use for quitting. Normally this character is C-g.
See section Quitting.
The current-input-mode
function returns the input mode settings
XEmacs is currently using.
This function returns current mode for reading keyboard input. It
returns a list, corresponding to the arguments of set-input-mode
,
of the form (interrupt flow meta quit)
in
which:
is non-nil
when XEmacs is using interrupt-driven input. If
nil
, Emacs is using CBREAK mode.
is non-nil
if XEmacs uses XON/XOFF (C-q, C-s)
flow control for output to the terminal. This value has no effect
unless interrupt is non-nil
.
is t
if XEmacs treats the eighth bit of input characters as
the meta bit; nil
means XEmacs clears the eighth bit of every
input character; any other value means XEmacs uses all eight bits as the
basic character code.
is the character XEmacs currently uses for quitting, usually C-g.
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This section describes features for translating input events into other input events before they become part of key sequences.
This console-local variable holds a keymap that describes the character sequences sent by function keys on an ordinary character terminal. This keymap uses the same data structure as other keymaps, but is used differently: it specifies translations to make while reading events.
If function-key-map
“binds” a key sequence k to a vector
v, then when k appears as a subsequence anywhere in a
key sequence, it is replaced with the events in v.
For example, VT100 terminals send <ESC> O P when the
keypad PF1 key is pressed. Therefore, we want XEmacs to translate
that sequence of events into the single event pf1
. We accomplish
this by “binding” <ESC> O P to [pf1]
in
function-key-map
, when using a VT100.
Thus, typing C-c <PF1> sends the character sequence C-c
<ESC> O P; later the function read-key-sequence
translates
this back into C-c <PF1>, which it returns as the vector
[?\C-c pf1]
.
Entries in 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.
The value of 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. XEmacs comes with
terminal-specific files for many common terminals; their main purpose is
to make entries in function-key-map
beyond those that can be
deduced from Termcap and Terminfo. See section Terminal-Specific Initialization.
Emacs versions 18 and earlier used totally different means of detecting the character sequences that represent function keys.
The parent keymap of function-key-map
is a non-console-local keymap,
function-key-map-parent
, and any additions to
function-key-map
that are not specific to a given console should
normally go into function-key-map-parent
rather than
function-key-map
.
This variable is another keymap used just like function-key-map
to translate input events into other events. It differs from
function-key-map
in two ways:
key-translation-map
goes to work after function-key-map
is
finished; it receives the results of translation by
function-key-map
.
key-translation-map
overrides actual key bindings.
The intent of key-translation-map
is for users to map one
character set to another, including ordinary characters normally bound
to self-insert-command
.
You can use function-key-map
or 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 read-key-sequence
—or 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 C-c h to turn the character that follows into a Hyper character:
(defun hyperify (prompt) (let ((e (read-event))) (vector (if (numberp e) (logior (lsh 1 20) 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)))) (if (symbolp e) symbol (cons symbol (cdr e))))) (define-key function-key-map "\C-ch" 'hyperify) |
The ‘iso-transl’ library uses this feature to provide a way of inputting non-ASCII Latin-1 characters.
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This function returns a vector containing recent input events from the
keyboard or mouse. By default, 100 events are recorded, which is how
many recent-keys
returns.
All input events are included, whether or not they were used as parts of key sequences. Thus, you always get the last 100 inputs, not counting keyboard macros. (Events from keyboard macros are excluded because they are less interesting for debugging; it should be enough to see the events that invoked the macros.)
If number is specified, not more than number events will be
returned. You may change the number of stored events using
set-recent-keys-ring-size
.
This function returns the number of recent events stored internally.
This is also the maximum number of events recent-keys
can
return. By default, 100 events are stored.
This function changes the number of events stored by XEmacs and returned
by recent-keys
.
For example, (set-recent-keys-ring-size 250)
will make XEmacs
remember last 250 events and will make recent-keys
return last
250 events by default.
This function opens a dribble file named filename. When a dribble file is open, each input event from the keyboard or mouse (but not those from keyboard macros) is written in that file. A non-character event is expressed using its printed representation surrounded by ‘<…>’.
You close the dribble file by calling this function with an argument
of nil
.
This function is normally used to record the input necessary to trigger an XEmacs bug, for the sake of a bug report.
(open-dribble-file "~/dribble") ⇒ nil |
See also the open-termscript
function (see section Terminal Output).
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The terminal output functions send output to the terminal or keep
track of output sent to the terminal. The function
device-baud-rate
tells you what XEmacs thinks is the output speed
of the terminal.
This function’s value is the output speed of the terminal associated with device, as far as XEmacs knows. device defaults to the selected device (usually the only device) if omitted. Changing this value does not change the speed of actual data transmission, but the value is used for calculations such as padding. This value has no effect for window-system devices. (This is different in FSF Emacs, where the baud rate also affects decisions about whether to scroll part of the screen or repaint, even when using a window system.)
The value is measured in bits per second.
XEmacs attempts to automatically initialize the baud rate by querying
the terminal. If you are running across a network, however, and
different parts of the network work are at different baud rates, the
value returned by XEmacs may be different from the value used by your
local terminal. Some network protocols communicate the local terminal
speed to the remote machine, so that XEmacs and other programs can get
the proper value, but others do not. If XEmacs has the wrong value, it
makes decisions that are less than optimal. To fix the problem, use
set-device-baud-rate
.
This function sets the output speed of device. See
device-baud-rate
. device defaults to the selected device
(usually the only device) if nil
.
This function sends char-or-string to the terminal without alteration. Control characters in char-or-string have terminal-dependent effects.
If device is nil
, this function writes to XEmacs’s
stderr, or to stdout if stdout-p is non-nil
. Otherwise,
device should be a tty or stream device, and the function writes
to the device’s normal or error output, according to stdout-p.
One use of this function is to define function keys on terminals that have downloadable function key definitions. For example, this is how on certain terminals to define function key 4 to move forward four characters (by transmitting the characters C-u C-f to the computer):
(send-string-to-terminal "\eF4\^U\^F") ⇒ nil |
This function is used to open a termscript file that will record
all the characters sent by XEmacs to the terminal. (If there are
multiple tty or stream devices, all characters sent to all such devices
are recorded.) The function returns nil
. Termscript files are
useful for investigating problems where XEmacs garbles the screen,
problems that are due to incorrect Termcap entries or to undesirable
settings of terminal options more often than to actual XEmacs bugs.
Once you are certain which characters were actually output, you can
determine reliably whether they correspond to the Termcap specifications
in use.
A nil
value for filename stops recording terminal output.
See also open-dribble-file
in Terminal Input.
(open-termscript "../junk/termscript") ⇒ nil |
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This section attempts to answer the question “Why does XEmacs choose to use flow-control characters in its command character set?” For a second view on this issue, read the comments on flow control in the ‘emacs/INSTALL’ file from the distribution; for help with Termcap entries and DEC terminal concentrators, see ‘emacs/etc/TERMS’.
At one time, most terminals did not need flow control, and none used
C-s
and C-q for flow control. Therefore, the choice of
C-s and C-q as command characters was uncontroversial.
XEmacs, for economy of keystrokes and portability, used nearly all the
ASCII control characters, with mnemonic meanings when possible;
thus, C-s for search and C-q for quote.
Later, some terminals were introduced which required these characters for flow control. They were not very good terminals for full-screen editing, so XEmacs maintainers did not pay attention. In later years, flow control with C-s and C-q became widespread among terminals, but by this time it was usually an option. And the majority of users, who can turn flow control off, were unwilling to switch to less mnemonic key bindings for the sake of flow control.
So which usage is “right”, XEmacs’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 C-s and 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 (which is very old), C-s and C-q were sent by the computer to turn the punch on and off!
As X servers and other window systems replace character-only
terminals, this problem is gradually being cured. For the mean time,
XEmacs provides a convenient way of enabling flow control if you want it:
call the function enable-flow-control
.
This function enables use of C-s and C-q for output flow
control, and provides the characters C-\ and C-^ as aliases
for them using keyboard-translate-table
(see section Translating Input Events).
With optional argument argument (interactively the prefix argument), enable flow control mode if argument is positive; else disable it.
You can use the function enable-flow-control-on
in your
‘.emacs’ file to enable flow control automatically on certain
terminal types.
This function enables flow control, and the aliases C-\ and C-^, if the terminal type is one of termtypes. For example:
(enable-flow-control-on "vt200" "vt300" "vt101" "vt131") |
Here is how enable-flow-control
does its job:
(set-input-mode nil t)
.
keyboard-translate-table
to translate C-\ and
C-^ into C-s and C-q. Except at its very
lowest level, XEmacs never knows that the characters typed were anything
but C-s and C-q, so you can in effect type them as C-\
and C-^ even when they are input for other commands.
See section Translating Input Events.
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 baud-rate
to a smaller value so that XEmacs uses a smaller
speed when calculating the padding needed. See section Terminal Output.
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