X-Git-Url: http://git.chise.org/gitweb/?a=blobdiff_plain;f=man%2Flispref%2Fos.texi;fp=man%2Flispref%2Fos.texi;h=67d1ff381274bf2c67252e8db2e09a6d03c8ac3b;hb=9a9fedfd2473568f4827f6295de7b03259b160e5;hp=0000000000000000000000000000000000000000;hpb=97badae7fa41c4bd3e92511ff7b16389e646e022;p=chise%2Fxemacs-chise.git- diff --git a/man/lispref/os.texi b/man/lispref/os.texi new file mode 100644 index 0000000..67d1ff3 --- /dev/null +++ b/man/lispref/os.texi @@ -0,0 +1,1701 @@ +@c -*-texinfo-*- +@c This is part of the XEmacs Lisp Reference Manual. +@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc. +@c See the file lispref.texi for copying conditions. +@setfilename ../../info/os.info +@node System Interface, X-Windows, Processes, Top +@chapter Operating System Interface + + This chapter is about starting and getting out of Emacs, access to +values in the operating system environment, and terminal input, output, +and flow control. + + @xref{Building XEmacs}, for related information. See also +@ref{Display}, for additional operating system status information +pertaining to the terminal and the screen. + +@menu +* Starting Up:: Customizing XEmacs start-up processing. +* Getting Out:: How exiting works (permanent or temporary). +* System Environment:: Distinguish the name and kind of system. +* User Identification:: Finding the name and user id of the user. +* Time of Day:: Getting the current time. +* Time Conversion:: Converting a time from numeric form to a string, or + to calendrical data (or vice versa). +* 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. +* Flow Control:: How to turn output flow control on or off. +* Batch Mode:: Running XEmacs without terminal interaction. +@end menu +@ignore +* Special Keysyms:: Defining system-specific key symbols for X windows. +@end ignore + +@node Starting Up +@section Starting Up XEmacs + + This section describes what XEmacs does when it is started, and how you +can customize these actions. + +@menu +* Start-up Summary:: Sequence of actions XEmacs performs at start-up. +* Init File:: Details on reading the init file (@file{.emacs}). +* Terminal-Specific:: How the terminal-specific Lisp file is read. +* Command Line Arguments:: How command line arguments are processed, + and how you can customize them. +@end menu + +@node Start-up Summary +@subsection Summary: Sequence of Actions at Start Up +@cindex initialization +@cindex start up of XEmacs +@cindex @file{startup.el} + + The order of operations performed (in @file{startup.el}) by XEmacs when +it is started up is as follows: + +@enumerate +@item +It loads the initialization library for the window system, if you are +using a window system. This library's name is +@file{term/@var{windowsystem}-win.el}. + +@item +It processes the initial options. (Some of them are handled +even earlier than this.) + +@item +It initializes the X window frame and faces, if appropriate. + +@item +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}. +@cindex @file{site-start.el} + +@item +It loads the file @file{~/.emacs} unless @samp{-q} was specified on +the command line. (This is not done in @samp{-batch} mode.) The @samp{-u} +option can specify the user name 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}. +@cindex @file{default.el} + +@item +It runs the normal hook @code{after-init-hook}. + +@item +It sets the major mode according to @code{initial-major-mode}, provided +the buffer @samp{*scratch*} is still current and still in Fundamental +mode. + +@item +It loads the terminal-specific Lisp file, if any, except when in batch +mode or using a window system. + +@item +It displays the initial echo area message, unless you have suppressed +that with @code{inhibit-startup-echo-area-message}. + +@item +It processes the action arguments from the command line. + +@item +It runs @code{term-setup-hook}. + +@item +It calls @code{frame-notice-user-settings}, which modifies the +parameters of the selected frame according to whatever the init files +specify. + +@item +It runs @code{window-setup-hook}. @xref{Terminal-Specific}. + +@item +It displays copyleft, nonwarranty, and basic use information, provided +there were no remaining command line arguments (a few steps above) and +the value of @code{inhibit-startup-message} is @code{nil}. +@end enumerate + +@defopt inhibit-startup-message +This variable inhibits the initial startup messages (the nonwarranty, +etc.). If it is non-@code{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. +@end defopt + +@defopt inhibit-startup-echo-area-message +This variable controls the display of the startup echo area message. +You can suppress the startup echo area message by adding text with this +form to your @file{.emacs} file: + +@example +(setq inhibit-startup-echo-area-message + "@var{your-login-name}") +@end example + +Simply setting @code{inhibit-startup-echo-area-message} to your login +name is not sufficient to inhibit the message; Emacs explicitly checks +whether @file{.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 @file{.emacs} file will not inhibit the +message for someone else. +@end defopt + +@node Init File +@subsection The Init File: @file{.emacs} +@cindex init file +@cindex @file{.emacs} + + When you start XEmacs, it normally attempts to load the file +@file{.emacs} from your home directory. This file, if it exists, must +contain Lisp code. It is called your @dfn{init file}. The command line +switches @samp{-q} and @samp{-u} affect the use of the init file; +@samp{-q} says not to load an init file, and @samp{-u} says to load a +specified user's init file instead of yours. @xref{Entering XEmacs,,, +xemacs, The XEmacs User's Manual}. + +@cindex default init file + A site may have a @dfn{default init file}, which is the library named +@file{default.el}. XEmacs finds the @file{default.el} file through the +standard search path for libraries (@pxref{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 @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 +XEmacs 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}. + +@defvar site-run-file +This variable specifies the site-customization file to load +before the user's init file. Its normal value is @code{"site-start"}. +@end defvar + + If there is a great deal of code in your @file{.emacs} file, you +should move it into another file named @file{@var{something}.el}, +byte-compile it (@pxref{Byte Compilation}), and make your @file{.emacs} +file load the other file using @code{load} (@pxref{Loading}). + + @xref{Init File Examples,,, xemacs, The XEmacs User's Manual}, for +examples of how to make various commonly desired customizations in your +@file{.emacs} file. + +@defopt inhibit-default-init +This variable prevents XEmacs from loading the default initialization +library file for your session of XEmacs. If its value is non-@code{nil}, +then the default library is not loaded. The default value is +@code{nil}. +@end defopt + +@defvar before-init-hook +@defvarx after-init-hook +These two normal hooks are run just before, and just after, loading of +the user's init file, @file{default.el}, and/or @file{site-start.el}. +@end defvar + +@node Terminal-Specific +@subsection Terminal-Specific Initialization +@cindex terminal-specific initialization + + Each terminal type can have its own Lisp library that XEmacs loads when +run on that type of terminal. For a terminal type named @var{termtype}, +the library is called @file{term/@var{termtype}}. XEmacs finds the file +by searching the @code{load-path} directories as it does for other +files, and trying the @samp{.elc} and @samp{.el} suffixes. Normally, +terminal-specific Lisp library is located in @file{emacs/lisp/term}, a +subdirectory of the @file{emacs/lisp} directory in which most XEmacs Lisp +libraries are kept.@refill + + The library's name is constructed by concatenating the value of the +variable @code{term-file-prefix} and the terminal type. Normally, +@code{term-file-prefix} has the value @code{"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 @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 + + Your @file{.emacs} file can prevent the loading of the +terminal-specific library by setting the variable +@code{term-file-prefix} to @code{nil}. This feature is useful when +experimenting with your own peculiar customizations. + + You can also arrange to override some of the actions of the +terminal-specific library by setting the variable +@code{term-setup-hook}. This is a normal hook which XEmacs runs using +@code{run-hooks} at the end of XEmacs initialization, after loading both +your @file{.emacs} file and any terminal-specific libraries. You can +use this variable to define initializations for terminals that do not +have their own libraries. @xref{Hooks}. + +@defvar term-file-prefix +@cindex @code{TERM} environment variable +If the @code{term-file-prefix} variable is non-@code{nil}, XEmacs loads +a terminal-specific initialization file as follows: + +@example +(load (concat term-file-prefix (getenv "TERM"))) +@end example + +@noindent +You may set the @code{term-file-prefix} variable to @code{nil} in your +@file{.emacs} file if you do not wish to load the +terminal-initialization file. To do this, put the following in +your @file{.emacs} file: @code{(setq term-file-prefix nil)}. +@end defvar + +@defvar term-setup-hook +This variable is a normal hook that XEmacs runs after loading your +@file{.emacs} file, the default initialization file (if any) and the +terminal-specific Lisp file. + +You can use @code{term-setup-hook} to override the definitions made by a +terminal-specific file. +@end defvar + +@defvar window-setup-hook +This variable is a normal hook which XEmacs runs after loading your +@file{.emacs} file and the default initialization file (if any), after +loading terminal-specific Lisp code, and after running the hook +@code{term-setup-hook}. +@end defvar + +@node Command Line Arguments +@subsection Command Line Arguments +@cindex command line arguments + + 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. + +@ignore + (Note that some other editors require you to start afresh each time +you want to edit a file. With this kind of editor, you will probably +specify the file as a command line argument. The recommended way to +use XEmacs is to start it only once, just after you log in, and do +all your editing in the same XEmacs process. Each time you want to edit +a different file, you visit it with the existing XEmacs, which eventually +comes to have many files in it ready for editing. Usually you do not +kill the XEmacs until you are about to log out.) +@end ignore + +@defun command-line +This function parses the command line that XEmacs was called with, +processes it, loads the user's @file{.emacs} file and displays the +startup messages. +@end defun + +@defvar command-line-processed +The value of this variable is @code{t} once the command line has been +processed. + +If you redump XEmacs by calling @code{dump-emacs}, you may wish to set +this variable to @code{nil} first in order to cause the new dumped XEmacs +to process its new command line arguments. +@end defvar + +@defvar command-switch-alist +@cindex switches on command line +@cindex options on command line +@cindex command line options +The value of this variable is an alist of user-defined command-line +options and associated handler functions. This variable exists so you +can add elements to it. + +A @dfn{command line option} is an argument on the command line of the +form: + +@example +-@var{option} +@end example + +The elements of the @code{command-switch-alist} look like this: + +@example +(@var{option} . @var{handler-function}) +@end example + +The @var{handler-function} is called to handle @var{option} and receives +the option name as its sole argument. + +In some cases, the option is followed in the command line by an +argument. In these cases, the @var{handler-function} can find all the +remaining command-line arguments in the variable +@code{command-line-args-left}. (The entire list of command-line +arguments is in @code{command-line-args}.) + +The command line arguments are parsed by the @code{command-line-1} +function in the @file{startup.el} file. See also @ref{Command +Switches, , Command Line Switches and Arguments, xemacs, The XEmacs +User's Manual}. +@end defvar + +@defvar command-line-args +The value of this variable is the list of command line arguments passed +to XEmacs. +@end defvar + +@defvar command-line-functions +This variable's value is a list of functions for handling an +unrecognized command-line argument. Each time the next argument to be +processed has no special meaning, the functions in this list are called, +in order of appearance, until one of them returns a non-@code{nil} +value. + +These functions are called with no arguments. They can access the +command-line argument under consideration through the variable +@code{argi}. The remaining arguments (not including the current one) +are in the variable @code{command-line-args-left}. + +When a function recognizes and processes the argument in @code{argi}, it +should return a non-@code{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 @code{command-line-args-left}. + +If all of these functions return @code{nil}, then the argument is used +as a file name to visit. +@end defvar + +@node Getting Out +@section Getting out of XEmacs +@cindex exiting XEmacs + + 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. + +@menu +* Killing XEmacs:: Exiting XEmacs irreversibly. +* Suspending XEmacs:: Exiting XEmacs reversibly. +@end menu + +@node Killing XEmacs +@subsection Killing XEmacs +@cindex killing XEmacs + + Killing XEmacs means ending the execution of the XEmacs process. The +parent process normally resumes control. The low-level primitive for +killing XEmacs is @code{kill-emacs}. + +@deffn Command kill-emacs &optional exit-data +This function exits the XEmacs process and kills it. + +If @var{exit-data} is an integer, then it is used as the exit status +of the XEmacs process. (This is useful primarily in batch operation; see +@ref{Batch Mode}.) + +If @var{exit-data} is a string, its contents are stuffed into the +terminal input buffer so that the shell (or whatever program next reads +input) can read them. +@end deffn + + 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 +@code{save-buffers-kill-emacs}. + +@defvar kill-emacs-query-functions +After asking the standard questions, @code{save-buffers-kill-emacs} +calls the functions in the list @code{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-@code{nil}, XEmacs is not killed. +@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. +@end defvar + +@node Suspending XEmacs +@subsection Suspending XEmacs +@cindex suspending XEmacs + + @dfn{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 @code{fg}. + + Some operating systems do not support suspension of jobs; on these +systems, ``suspension'' actually creates a new shell temporarily as a +subprocess of 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. + +@deffn Command suspend-emacs &optional stuffstring +This function stops XEmacs and returns control to the superior process. +If and when the superior process resumes XEmacs, @code{suspend-emacs} +returns @code{nil} to its caller in Lisp. + +If optional arg @var{stuffstring} is non-@code{nil}, its characters are +sent to be read as terminal input by XEmacs's superior shell. The +characters in @var{stuffstring} are not echoed by the superior shell; +only the results appear. + +Before suspending, @code{suspend-emacs} runs the normal hook +@code{suspend-hook}. In Emacs version 18, @code{suspend-hook} was not a +normal hook; its value was a single function, and if its value was +non-@code{nil}, then @code{suspend-emacs} returned immediately without +actually suspending anything. + +After the user resumes XEmacs, @code{suspend-emacs} runs the normal hook +@code{suspend-resume-hook}. @xref{Hooks}. + +The next redisplay after resumption will redraw the entire screen, +unless the variable @code{no-redraw-on-reenter} is non-@code{nil} +(@pxref{Refresh Screen}). + +In the following example, note that @samp{pwd} is not echoed after +XEmacs is suspended. But it is read and executed by the shell. + +@smallexample +@group +(suspend-emacs) + @result{} nil +@end group + +@group +(add-hook 'suspend-hook + (function (lambda () + (or (y-or-n-p + "Really suspend? ") + (error "Suspend cancelled"))))) + @result{} (lambda nil + (or (y-or-n-p "Really suspend? ") + (error "Suspend cancelled"))) +@end group +@group +(add-hook 'suspend-resume-hook + (function (lambda () (message "Resumed!")))) + @result{} (lambda nil (message "Resumed!")) +@end group +@group +(suspend-emacs "pwd") + @result{} nil +@end group +@group +---------- Buffer: Minibuffer ---------- +Really suspend? @kbd{y} +---------- Buffer: Minibuffer ---------- +@end group + +@group +---------- Parent Shell ---------- +lewis@@slug[23] % /user/lewis/manual +lewis@@slug[24] % fg +@end group + +@group +---------- Echo Area ---------- +Resumed! +@end group +@end smallexample +@end deffn + +@defvar suspend-hook +This variable is a normal hook run before suspending. +@end defvar + +@defvar suspend-resume-hook +This variable is a normal hook run after suspending. +@end defvar + +@node System Environment +@section Operating System Environment +@cindex operating system environment + + XEmacs provides access to variables in the operating system environment +through various functions. These variables include the name of the +system, the user's @sc{uid}, and so on. + +@defvar system-type +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: + +@table @code +@item aix-v3 +AIX. + +@item berkeley-unix +Berkeley BSD. + +@item dgux +Data General DGUX operating system. + +@item gnu +A GNU system using the GNU HURD and Mach. + +@item hpux +Hewlett-Packard HPUX operating system. + +@item irix +Silicon Graphics Irix system. + +@item linux +A GNU system using the Linux kernel. + +@item ms-dos +Microsoft MS-DOS ``operating system.'' + +@item next-mach +NeXT Mach-based system. + +@item rtu +Masscomp RTU, UCB universe. + +@item unisoft-unix +UniSoft UniPlus. + +@item usg-unix-v +AT&T System V. + +@item windows-nt +Microsoft windows NT. + +@item xenix +SCO Xenix 386. +@end table + +We do not wish to add new symbols to make finer distinctions unless it +is absolutely necessary! In fact, we hope to eliminate some of these +alternatives in the future. We recommend using +@code{system-configuration} to distinguish between different operating +systems. +@end defvar + +@defvar system-configuration +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 @code{string-match}. +@end defvar + +@defun system-name +This function returns the name of the machine you are running on. +@example +(system-name) + @result{} "prep.ai.mit.edu" +@end example +@end defun + +@vindex system-name + The symbol @code{system-name} is a variable as well as a function. In +fact, the function returns whatever value the variable +@code{system-name} currently holds. Thus, you can set the variable +@code{system-name} in case Emacs is confused about the name of your +system. The variable is also useful for constructing frame titles +(@pxref{Frame Titles}). + +@defvar mail-host-address +If this variable is non-@code{nil}, it is used instead of +@code{system-name} for purposes of generating email addresses. For +example, it is used when constructing the default value of +@code{user-mail-address}. @xref{User Identification}. (Since this is +done when XEmacs starts up, the value actually used is the one saved when +XEmacs was dumped. @xref{Building XEmacs}.) +@end defvar + +@deffn Command getenv var &optional interactivep +@cindex environment variable access +This function returns the value of the environment variable @var{var}, +as a string. Within XEmacs, the environment variable values are kept in +the Lisp variable @code{process-environment}. + +When invoked interactively, @code{getenv} prints the value in the echo area. + +@example +@group +(getenv "USER") + @result{} "lewis" +@end group + +@group +lewis@@slug[10] % printenv +PATH=.:/user/lewis/bin:/usr/bin:/usr/local/bin +USER=lewis +@end group +@group +TERM=ibmapa16 +SHELL=/bin/csh +HOME=/user/lewis +@end group +@end example +@end deffn + +@deffn Command setenv variable &optional value unset +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. +@end deffn + +@defvar process-environment +This variable is a list of strings, each describing one environment +variable. The functions @code{getenv} and @code{setenv} work by +manipulating this variable. + +@smallexample +@group +process-environment +@result{} ("l=/usr/stanford/lib/gnuemacs/lisp" + "PATH=.:/user/lewis/bin:/usr/class:/nfsusr/local/bin" + "USER=lewis" +@end group +@group + "TERM=ibmapa16" + "SHELL=/bin/csh" + "HOME=/user/lewis") +@end group +@end smallexample +@end defvar + +@defvar path-separator +This variable holds a string which says which character separates +directories in a search path (as found in an environment variable). Its +value is @code{":"} for Unix and GNU systems, and @code{";"} for MS-DOS +and Windows NT. +@end defvar + +@defvar invocation-name +This variable holds the program name under which Emacs was invoked. The +value is a string, and does not include a directory name. +@end defvar + +@defvar invocation-directory +This variable holds the directory from which the Emacs executable was +invoked, or perhaps @code{nil} if that directory cannot be determined. +@end defvar + +@defvar installation-directory +If non-@code{nil}, this is a directory within which to look for the +@file{lib-src} and @file{etc} subdirectories. This is non-@code{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. +@end defvar + +@defun load-average &optional use-floats +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 @var{use-floats} is non-@code{nil}, floats will be returned instead +of integers. These floats are not multiplied by 100. + +@example +@group +(load-average) + @result{} (169 158 164) +(load-average t) + @result{} (1.69921875 1.58984375 1.640625) +@end group + +@group +lewis@@rocky[5] % uptime + 8:06pm up 16 day(s), 21:57, 40 users, + load average: 1.68, 1.59, 1.64 +@end group +@end example + +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. +@end defun + +@defun emacs-pid +This function returns the process @sc{id} of the Emacs process. +@end defun + +@node User Identification +@section User Identification + +@defvar user-mail-address +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. +@end defvar + +@defun user-login-name &optional uid +If you don't specify @var{uid}, this function returns the name under +which the user is logged in. If the environment variable @code{LOGNAME} +is set, that value is used. Otherwise, if the environment variable +@code{USER} is set, that value is used. Otherwise, the value is based +on the effective @sc{uid}, not the real @sc{uid}. + +If you specify @var{uid}, the value is the user name that corresponds +to @var{uid} (which should be an integer). + +@example +@group +(user-login-name) + @result{} "lewis" +@end group +@end example +@end defun + +@defun user-real-login-name +This function returns the user name corresponding to Emacs's real +@sc{uid}. This ignores the effective @sc{uid} and ignores the +environment variables @code{LOGNAME} and @code{USER}. +@end defun + +@defvar user-full-name +This variable holds the name of the user running this Emacs. It is +initialized at startup time from the value of @code{NAME} environment +variable. You can change the value of this variable to alter the result +of the @code{user-full-name} function. +@end defvar + +@defun user-full-name &optional user +This function returns the full name of @var{user}. If @var{user} is +@code{nil}, it defaults to the user running this Emacs. In that case, +the value of @code{user-full-name} variable, if non-@code{nil}, will be +used. + +If @var{user} is specified explicitly, @code{user-full-name} variable is +ignored. + +@example +@group +(user-full-name) + @result{} "Hrvoje Niksic" +(setq user-full-name "Hrvoje \"Niksa\" Niksic") +(user-full-name) + @result{} "Hrvoje \"Niksa\" Niksic" +(user-full-name "hniksic") + @result{} "Hrvoje Niksic" +@end group +@end example +@end defun + +@vindex user-full-name +@vindex user-real-login-name +@vindex user-login-name + The symbols @code{user-login-name}, @code{user-real-login-name} and +@code{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 (@pxref{Frame +Titles}). + +@defun user-real-uid +This function returns the real @sc{uid} of the user. + +@example +@group +(user-real-uid) + @result{} 19 +@end group +@end example +@end defun + +@defun user-uid +This function returns the effective @sc{uid} of the user. +@end defun + +@defun user-home-directory +This function returns the ``@code{HOME}'' directory of the user, and is +intended to replace occurrences of ``@code{(getenv "HOME")}''. Under +Unix systems, the following is done: + +@enumerate +@item +Return the value of ``@code{(getenv "HOME")}'', if set. + +@item +Return ``/'', as a fallback, but issue a warning. (Future versions of +XEmacs will also attempt to lookup the @code{HOME} directory via +@code{getpwent()}, but this has not yet been implemented.) +@end enumerate + +Under MS Windows, this is done: + +@enumerate +@item +Return the value of ``@code{(getenv "HOME")}'', if set. + +@item +If the environment variables @code{HOMEDRIVE} and @code{HOMEDIR} are +both set, return the concatenation (the following description uses MS +Windows environment variable substitution syntax): +@code{%HOMEDRIVE%%HOMEDIR%}. + +@item +Return ``C:\'', as a fallback, but issue a warning. +@end enumerate +@end defun + +@node Time of Day +@section Time of Day + + This section explains how to determine the current time and the time +zone. + +@defun current-time-string &optional time-value +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 +@code{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. + +@c Emacs 19 feature +The argument @var{time-value}, if given, specifies a time to format +instead of the current time. The argument should be a list whose first +two elements are integers. Thus, you can use times obtained from +@code{current-time} (see below) and from @code{file-attributes} +(@pxref{File Attributes}). + +@example +@group +(current-time-string) + @result{} "Wed Oct 14 22:21:05 1987" +@end group +@end example +@end defun + +@c Emacs 19 feature +@defun current-time +This function returns the system's time value as a list of three +integers: @code{(@var{high} @var{low} @var{microsec})}. The integers +@var{high} and @var{low} combine to give the number of seconds since +0:00 January 1, 1970, which is +@ifinfo +@var{high} * 2**16 + @var{low}. +@end ifinfo +@tex +$high*2^{16}+low$. +@end tex + +The third element, @var{microsec}, gives the microseconds since the +start of the current second (or 0 for systems that return time only on +the resolution of a second). + +The first two elements can be compared with file time values such as you +get with the function @code{file-attributes}. @xref{File Attributes}. +@end defun + +@c Emacs 19 feature +@defun current-time-zone &optional time-value +This function returns a list describing the time zone that the user is +in. + +The value has the form @code{(@var{offset} @var{name})}. Here +@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; +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}. + +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}). +@end defun + +@node Time Conversion +@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}). + +@defun format-time-string format-string &optional time +This function converts @var{time} to a string according to +@var{format-string}. If @var{time} is omitted, it defaults to the +current time. The argument @var{format-string} may contain +@samp{%}-sequences which say to substitute parts of the time. Here is a +table of what the @samp{%}-sequences mean: + +@table @samp +@item %a +This stands for the abbreviated name of the day of week. +@item %A +This stands for the full name of the day of week. +@item %b +This stands for the abbreviated name of the month. +@item %B +This stands for the full name of the month. +@item %c +This is a synonym for @samp{%x %X}. +@item %C +This has a locale-specific meaning. In the default locale (named C), it +is equivalent to @samp{%A, %B %e, %Y}. +@item %d +This stands for the day of month, zero-padded. +@item %D +This is a synonym for @samp{%m/%d/%y}. +@item %e +This stands for the day of month, blank-padded. +@item %h +This is a synonym for @samp{%b}. +@item %H +This stands for the hour (00-23). +@item %I +This stands for the hour (00-12). +@item %j +This stands for the day of the year (001-366). +@item %k +This stands for the hour (0-23), blank padded. +@item %l +This stands for the hour (1-12), blank padded. +@item %m +This stands for the month (01-12). +@item %M +This stands for the minute (00-59). +@item %n +This stands for a newline. +@item %p +This stands for @samp{AM} or @samp{PM}, as appropriate. +@item %r +This is a synonym for @samp{%I:%M:%S %p}. +@item %R +This is a synonym for @samp{%H:%M}. +@item %S +This stands for the seconds (00-60). +@item %t +This stands for a tab character. +@item %T +This is a synonym for @samp{%H:%M:%S}. +@item %U +This stands for the week of the year (01-52), assuming that weeks +start on Sunday. +@item %w +This stands for the numeric day of week (0-6). Sunday is day 0. +@item %W +This stands for the week of the year (01-52), assuming that weeks +start on Monday. +@item %x +This has a locale-specific meaning. In the default locale (named C), it +is equivalent to @samp{%D}. +@item %X +This has a locale-specific meaning. In the default locale (named C), it +is equivalent to @samp{%T}. +@item %y +This stands for the year without century (00-99). +@item %Y +This stands for the year with century. +@item %Z +This stands for the time zone abbreviation. +@end table +@end defun + +@defun decode-time &optional specified-time +This function converts a time value into calendrical information. The +optional @var{specified-time} should be a list of +(@var{high} @var{low} . @var{ignored}) or (@var{high} . @var{low}), as from +@code{current-time} and @code{file-attributes}, or @code{nil} to use 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 sec +The number of seconds past the minute, as an integer between 0 and 59. +@item minute +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 + +Note that 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 treated just like other year numbers. If +you want them to stand for years above 1900, you must alter them yourself +before you call @code{encode-time}. + +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}) or an integer (as you +would get from @code{decode-time}). The specified zone is used without +any further alteration for daylight savings time. +@end defun + +@node Timers +@section Timers for Delayed Execution + +You can set up a timer to call a function at a specified future time. + +@c All different in FSF 19 +@defun add-timeout secs function object &optional resignal +This function adds a timeout, to be signaled after the timeout period +has elapsed. @var{secs} is a number of seconds, expressed as an integer +or a float. @var{function} will be called after that many seconds have +elapsed, with one argument, the given @var{object}. If the optional +@var{resignal} argument is provided, then after this timeout expires, +@code{add-timeout} will automatically be called again with +@var{resignal} as the first argument. + +This function returns an object which is the @dfn{id} of this particular +timeout. You can pass that object to @code{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 +@code{next-event}, and the function will be invoked by +@code{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 @var{resignal} argument exists. + +(NOTE: In FSF Emacs, this function is called @code{run-at-time} and +has different semantics.) +@end defun + +@defun disable-timeout id +Cancel the requested action for @var{id}, which should be a value +previously returned by @code{add-timeout}. This cancels the effect of +that call to @code{add-timeout}; the arrival of the specified time will +not cause anything special to happen. +(NOTE: In FSF Emacs, this function is called @code{cancel-timer}.) +@end defun + +@node Terminal Input +@section Terminal Input +@cindex terminal input + + This section describes functions and variables for recording or +manipulating terminal input. See @ref{Display}, for related +functions. + +@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 + +@node Input Modes +@subsection Input Modes +@cindex input modes +@cindex terminal input modes + +@defun set-input-mode interrupt flow meta &optional quit-char console +This function sets the mode for reading keyboard input. If +@var{interrupt} is non-null, then XEmacs uses input interrupts. If it is +@code{nil}, then it uses @sc{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 @var{flow} is non-@code{nil}, then XEmacs 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}. + +The default setting is system dependent. Some systems always use +@sc{cbreak} mode regardless of what is specified. + +@c Emacs 19 feature +The argument @var{meta} controls support for input character codes +above 127. If @var{meta} is @code{t}, XEmacs converts characters with +the 8th bit set into Meta characters. If @var{meta} is @code{nil}, +XEmacs disregards the 8th bit; this is necessary when the terminal uses +it as a parity bit. If @var{meta} is neither @code{t} nor @code{nil}, +XEmacs uses all 8 bits of input unchanged. This is good for terminals +using European 8-bit character sets. + +@c Emacs 19 feature +If @var{quit-char} is non-@code{nil}, it specifies the character to +use for quitting. Normally this character is @kbd{C-g}. +@xref{Quitting}. +@end defun + +The @code{current-input-mode} function returns the input mode settings +XEmacs is currently using. + +@c Emacs 19 feature +@defun current-input-mode &optional console +This function returns current mode for reading keyboard input. It +returns a list, corresponding to the arguments of @code{set-input-mode}, +of the form @code{(@var{interrupt} @var{flow} @var{meta} @var{quit})} in +which: +@table @var +@item interrupt +is non-@code{nil} when XEmacs is using interrupt-driven input. If +@code{nil}, Emacs is using @sc{cbreak} mode. +@item flow +is non-@code{nil} if XEmacs uses @sc{xon/xoff} (@kbd{C-q}, @kbd{C-s}) +flow control for output to the terminal. This value has no effect +unless @var{interrupt} is non-@code{nil}. +@item meta +is @code{t} if XEmacs treats the eighth bit of input characters as +the meta bit; @code{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. +@item quit +is the character XEmacs currently uses for quitting, usually @kbd{C-g}. +@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. + +@ignore Not in XEmacs yet. +@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 X windows, 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 must be a string or @code{nil}. + +If @code{keyboard-translate-table} is a string, then each character read +from the keyboard is looked up in this string and the character in the +string is used instead. If the string is of length @var{n}, character codes +@var{n} and up are untranslated. + +In the example below, we set @code{keyboard-translate-table} to a +string of 128 characters. 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 + (let ((the-table (make-string 128 0))) + (let ((i 0)) + (while (< i 128) + (aset the-table i i) + (setq i (1+ i)))) +@end group + ;; @r{Swap @kbd{C-s} and @kbd{C-\}.} + (aset the-table ?\034 ?\^s) + (aset the-table ?\^s ?\034) +@group + ;; @r{Swap @kbd{C-q} and @kbd{C-^}.} + (aset the-table ?\036 ?\^q) + (aset the-table ?\^q ?\036) + (setq keyboard-translate-table the-table))) +@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 &rest pairs +This function modifies @code{keyboard-translate-table} to translate +character code @var{from} into character code @var{to}. It creates +or enlarges the translate table if necessary. Multiple +@var{from}-@var{to} pairs may be specified. +@end defun +@end ignore + +@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 +uses the same data structure as other keymaps, but is used differently: it +specifies translations to make while reading events. + +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 PF1 key is pressed. Therefore, we want XEmacs 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. + +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. XEmacs 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}. + +Emacs versions 18 and earlier used totally different means of detecting +the character sequences that represent function keys. +@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. +@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 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)))) +@end group +@group + (if (symbolp e) + symbol + (cons symbol (cdr e))))) + +(define-key function-key-map "\C-ch" 'hyperify) +@end group +@end example + +@pindex iso-transl +@cindex Latin-1 character set (input) +@cindex ISO Latin-1 characters (input) +The @file{iso-transl} library uses this feature to provide a way of +inputting non-ASCII Latin-1 characters. + +@node Recording Input +@subsection Recording Input + +@defun recent-keys &optional number +This function returns a vector containing recent input events from the +keyboard or mouse. By default, 100 events are recorded, which is how +many @code{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 @var{number} is specified, not more than @var{number} events will be +returned. You may change the number of stored events using +@code{set-recent-keys-ring-size}. +@end defun + +@defun recent-keys-ring-size +This function returns the number of recent events stored internally. +This is also the maximum number of events @code{recent-keys} can +return. By default, 100 events are stored. +@end defun + +@defun set-recent-keys-ring-size size +This function changes the number of events stored by XEmacs and returned +by @code{recent-keys}. + +For example, @code{(set-recent-keys-ring-size 250)} will make XEmacs +remember last 250 events and will make @code{recent-keys} return last +250 events by default. +@end defun + +@deffn Command open-dribble-file filename +@cindex dribble file +This function opens a @dfn{dribble file} named @var{filename}. When a +dribble file is open, each input event from the keyboard or mouse (but +not those from keyboard macros) is written in that file. A +non-character event is expressed using its printed representation +surrounded by @samp{<@dots{}>}. + +You close the dribble file by calling this function with an argument +of @code{nil}. + +This function is normally used to record the input necessary to +trigger an XEmacs bug, for the sake of a bug report. + +@example +@group +(open-dribble-file "~/dribble") + @result{} nil +@end group +@end example +@end deffn + + See also the @code{open-termscript} function (@pxref{Terminal Output}). + +@node Terminal Output +@section Terminal Output +@cindex terminal output + + The terminal output functions send output to the terminal or keep +track of output sent to the terminal. The function +@code{device-baud-rate} tells you what XEmacs thinks is the output speed +of the terminal. + +@defun device-baud-rate &optional device +This function's value is the output speed of the terminal associated +with @var{device}, as far as XEmacs knows. @var{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. +@end defun + +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 +@code{set-device-baud-rate}. + +@defun set-device-baud-rate device baud-rate +This function sets the output speed of @var{device}. See +@code{device-baud-rate}. @var{device} defaults to the selected device +(usually the only device) if @code{nil}. +@end defun + +@defun send-string-to-terminal char-or-string &optional stdout-p device +This function sends @var{char-or-string} to the terminal without +alteration. Control characters in @var{char-or-string} have +terminal-dependent effects. + +If @var{device} is @code{nil}, this function writes to XEmacs's +stderr, or to stdout if @var{stdout-p} is non-@code{nil}. Otherwise, +@var{device} should be a tty or stream device, and the function writes +to the device's normal or error output, according to @var{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 @kbd{C-u C-f} to the +computer): + +@example +@group +(send-string-to-terminal "\eF4\^U\^F") + @result{} nil +@end group +@end example +@end defun + +@deffn Command open-termscript filename +@cindex termscript file +This function is used to open a @dfn{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 @code{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 @code{nil} value for @var{filename} stops recording terminal output. + +See also @code{open-dribble-file} in @ref{Terminal Input}. + +@example +@group +(open-termscript "../junk/termscript") + @result{} nil +@end group +@end example +@end deffn + +@ignore Not in XEmacs +@node Special Keysyms +@section System-Specific X11 Keysyms + +To define system-specific X11 keysyms, set the variable +@code{system-key-alist}. + +@defvar system-key-alist +This variable's value should be an alist with one element for each +system-specific keysym. An element has this form: @code{(@var{code} +. @var{symbol})}, where @var{code} is the numeric keysym code (not +including the ``vendor specific'' bit, 1 << 28), and @var{symbol} is the +name for the function key. + +For example @code{(168 . mute-acute)} defines a system-specific key used +by HP X servers whose numeric code is (1 << 28) + 168. + +It is not a problem if the alist defines keysyms for other X servers, as +long as they don't conflict with the ones used by the X server actually +in use. + +The variable is always local to the current X terminal and cannot be +buffer-local. @xref{Multiple Displays}. +@end defvar +@end ignore + +@node Flow Control +@section Flow Control +@cindex flow control characters + + 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 +@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 was uncontroversial. +XEmacs, for economy of keystrokes and portability, used nearly all the +@sc{ascii} control characters, with mnemonic meanings when possible; +thus, @kbd{C-s} for search and @kbd{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 @kbd{C-s} and @kbd{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 +@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 (which is very old), @kbd{C-s} +and @kbd{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 @code{enable-flow-control}. + +@deffn Command enable-flow-control &optional argument +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}). + +With optional argument @var{argument} (interactively the prefix +argument), enable flow control mode if @var{argument} is positive; else +disable it. +@end deffn + +You can use the function @code{enable-flow-control-on} in your +@file{.emacs} 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, XEmacs 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 XEmacs 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 XEmacs to run +noninteractively. In this mode, XEmacs does not read commands from the +terminal, it does not alter the terminal modes, and it does not expect +to be outputting to an erasable screen. The idea is that you specify +Lisp programs to run; when they are finished, XEmacs 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. + + Any Lisp program output that would normally go to the echo area, +either using @code{message} or using @code{prin1}, etc., with @code{t} +as the stream, goes instead to XEmacs's standard error descriptor when +in batch mode. Thus, XEmacs behaves much like a noninteractive +application program. (The echo area output that XEmacs itself normally +generates, such as command echoing, is suppressed entirely.) + +@defun noninteractive +This function returns non-@code{nil} when XEmacs is running in batch mode. +@end defun + +@defvar noninteractive +This variable is non-@code{nil} when XEmacs is running in batch mode. +Setting this variable to @code{nil}, however, will not change whether +XEmacs is running in batch mode, and will not change the return value +of the @code{noninteractive} function. +@end defvar