This is Info file elisp, produced by Makeinfo-1.55 from the input file elisp.texi. This version is the edition 2.3 of the GNU Emacs Lisp Reference Manual. It corresponds to Emacs Version 19.23. Published by the Free Software Foundation 675 Massachusetts Avenue Cambridge, MA 02139 USA Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled "GNU General Public License" is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled "GNU General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English.  File: elisp, Node: TCP, Prev: Transaction Queues, Up: Processes TCP === Emacs Lisp programs can open TCP connections to other processes on the same machine or other machines. A network connection is handled by Lisp much like a subprocess, and is represented by a process object. However, the process you are communicating with is not a child of the Emacs process, so you can't kill it or send it signals. All you can do is send and receive data. `delete-process' closes the connection, but does not kill the process at the other end; that process must decide what to do about closure of the connection. You can distinguish process objects representing network connections from those representing subprocesses with the `process-status' function. *Note Process Information::. -- Function: open-network-stream NAME BUFFER-OR-NAME HOST SERVICE This function opens a TCP connection for a service to a host. It returns a process object to represent the connection. The NAME argument specifies the name for the process object. It is modified as necessary to make it unique. The BUFFER-OR-NAME argument is the buffer to associate with the connection. Output from the connection is inserted in the buffer, unless you specify a filter function to handle the output. If BUFFER-OR-NAME is `nil', it means that the connection is not associated with any buffer. The arguments HOST and SERVICE specify where to connect to; HOST is the host name (a string), and SERVICE is the name of a defined network service (a string) or a port number (an integer).  File: elisp, Node: System Interface, Next: Display, Prev: Processes, Up: Top 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. *Note Building Emacs::, for related information. See also *Note Display::, for additional operating system status information pertaining to the terminal and the screen. * Menu: * Starting Up:: Customizing Emacs 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. * Timers:: Setting a timer to call a function at a certain time. * Terminal Input:: Recording terminal input for debugging. * Terminal Output:: Recording terminal output for debugging. * Special Keysyms:: Defining system-specific key symbols for X windows. * Flow Control:: How to turn output flow control on or off. * Batch Mode:: Running Emacs without terminal interaction.  File: elisp, Node: Starting Up, Next: Getting Out, Up: System Interface Starting Up Emacs ================= This section describes what Emacs does when it is started, and how you can customize these actions. * Menu: * Start-up Summary:: Sequence of actions Emacs performs at start-up. * Init File:: Details on reading the init 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.  File: elisp, Node: Start-up Summary, Next: Init File, Up: Starting Up Summary: Sequence of Actions at Start Up ---------------------------------------- The order of operations performed (in `startup.el') by Emacs when it is started up is as follows: 1. It loads the initialization library for the window system, if you are using a window system. This library's name is `term/WINDOWSYSTEM-win.el'. 2. It initializes the X window frame and faces, if appropriate. 3. It runs the normal hook `before-init-hook'. 4. It loads the library `site-start', unless the option `-no-site-file' was specified. The library's file name is usually `site-start.el'. 5. It loads the file `~/.emacs' unless `-q' was specified on command line. (This is not done in `-batch' mode.) The `-u' option can specify the user name whose home directory should be used instead of `~'. 6. It loads the library `default' unless `inhibit-default-init' is non-`nil'. (This is not done in `-batch' mode or if `-q' was specified on command line.) The library's file name is usually `default.el'. 7. It runs the normal hook `after-init-hook'. 8. It sets the major mode according to `initial-major-mode', provided the buffer `*scratch*' is still current and still in Fundamental mode. 9. It loads the terminal-specific Lisp file, if any, except when in batch mode or using a window system. 10. It displays the initial echo area message, unless you have suppressed that with `inhibit-startup-echo-area-message'. 11. It processes any remaining command line arguments. 12. It runs `term-setup-hook'. 13. It calls `frame-notice-user-settings', which modifies the parameters of the selected frame according to whatever the init files specify. 14. It runs `window-setup-hook'. *Note Window Systems::. 15. It displays copyleft, nonwarranty and basic use information, provided there were no remaining command line arguments (a few steps above) and the value of `inhibit-startup-message' is `nil'. -- User Option: inhibit-startup-message 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. -- User Option: 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 `.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.  File: elisp, Node: Init File, Next: Terminal-Specific, Prev: Start-up Summary, Up: Starting Up The Init File: `.emacs' ----------------------- When you start Emacs, 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. *Note Entering Emacs: (emacs)Entering Emacs. A site may have a "default init file", which is the library named `default.el'. Emacs finds the `default.el' file through the standard search path for libraries (*note How Programs Do Loading::.). The Emacs distribution does not come with this file; sites may provide one for local customizations. If the default init file exists, it is loaded whenever you start Emacs, except in batch mode or if `-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 Emacs 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'. 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 (*note Byte Compilation::.), and make your `.emacs' file load the other file using `load' (*note Loading::.). *Note Init File Examples: (emacs)Init File Examples, for examples of how to make various commonly desired customizations in your `.emacs' file. -- User Option: inhibit-default-init This variable prevents Emacs from loading the default initialization library file for your session of Emacs. If its value is non-`nil', then the default library is not loaded. The default value is `nil'. -- Variable: before-init-hook -- Variable: after-init-hook 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'.  File: elisp, Node: Terminal-Specific, Next: Command Line Arguments, Prev: Init File, Up: Starting Up Terminal-Specific Initialization -------------------------------- Each terminal type can have its own Lisp library that Emacs loads when run on that type of terminal. For a terminal type named TERMTYPE, the library is called `term/TERMTYPE'. Emacs 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 Emacs 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 Emacs 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. *Note 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 Emacs runs using `run-hooks' at the end of Emacs 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. *Note Hooks::. -- Variable: term-file-prefix If the `term-file-prefix' variable is non-`nil', Emacs 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)'. -- Variable: term-setup-hook This variable is a normal hook which Emacs 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. See `window-setup-hook' in *Note Window Systems::, for a related feature.  File: elisp, Node: Command Line Arguments, Prev: Terminal-Specific, Up: Starting Up Command Line Arguments ---------------------- You can use command line arguments to request various actions when you start Emacs. Since you do not need to start Emacs more than once per day, and will often leave your Emacs session running longer than that, command line arguments are hardly ever used. As a practical matter, it is best to avoid making the habit of using them, since this habit would encourage you to kill and restart Emacs unnecessarily often. These options exist for two reasons: to be compatible with other editors (for invocation by other programs) and to enable shell scripts to run specific Lisp programs. This section describes how Emacs processes command line arguments, and how you can customize them. -- Function: command-line This function parses the command line which Emacs was called with, processes it, loads the user's `.emacs' file and displays the initial nonwarranty information, etc. -- Variable: command-line-processed The value of this variable is `t' once the command line has been processed. If you redump Emacs by calling `dump-emacs', you may wish to set this variable to `nil' first in order to cause the new dumped Emacs to process its new command line arguments. -- Variable: command-switch-alist 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 *Note Command Line Switches and Arguments: (emacs)Command Switches. -- Variable: command-line-args The value of this variable is the list of command line arguments passed to Emacs. -- Variable: 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 the order they appear, 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.  File: elisp, Node: Getting Out, Next: System Environment, Prev: Starting Up, Up: System Interface Getting Out of Emacs ==================== There are two ways to get out of Emacs: you can kill the Emacs job, which exits permanently, or you can suspend it, which permits you to reenter the Emacs process later. As a practical matter, you seldom kill Emacs---only when you are about to log out. Suspending is much more common. * Menu: * Killing Emacs:: Exiting Emacs irreversibly. * Suspending Emacs:: Exiting Emacs reversibly.  File: elisp, Node: Killing Emacs, Next: Suspending Emacs, Up: Getting Out Killing Emacs ------------- Killing Emacs means ending the execution of the Emacs process. The parent process normally resumes control. The low-level primitive for killing Emacs is `kill-emacs'. -- Function: kill-emacs &optional EXIT-DATA This function exits the Emacs process and kills it. If EXIT-DATA is an integer, then it is used as the exit status of the Emacs process. (This is useful primarily in batch operation; see *Note 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 Emacs process, aside from files that have been saved, is lost when the Emacs is killed. Because killing Emacs inadvertently can lose a lot of work, Emacs queries for confirmation before actually terminating if you have buffers that need saving or subprocesses that are running. This is done in the function `save-buffers-kill-emacs'. -- Variable: kill-emacs-query-functions 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', Emacs is not killed. -- Variable: kill-emacs-hook 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.  File: elisp, Node: Suspending Emacs, Prev: Killing Emacs, Up: Getting Out Suspending Emacs ---------------- "Suspending Emacs" means stopping Emacs temporarily and returning control to its superior process, which is usually the shell. This allows you to resume editing later in the same Emacs process, with the same buffers, the same kill ring, the same undo history, and so on. To resume Emacs, 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 Emacs. Then you would exit the shell to return to Emacs. Suspension is not useful with window systems such as X, because the Emacs 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 Emacs is an X client. -- Function: suspend-emacs STRING This function stops Emacs and returns control to the superior process. If and when the superior process resumes Emacs, `suspend-emacs' returns `nil' to its caller in Lisp. If STRING is non-`nil', its characters are sent to be read as terminal input by Emacs's superior shell. The characters in STRING 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 Emacs, it runs the normal hook `suspend-resume-hook'. *Note Hooks::. The next redisplay after resumption will redraw the entire screen, unless the variable `no-redraw-on-reenter' is non-`nil' (*note Refresh Screen::.). In the following example, note that `pwd' is not echoed after Emacs 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! -- Variable: suspend-hook This variable is a normal hook run before suspending. -- Variable: suspend-resume-hook This variable is a normal hook run after suspending.  File: elisp, Node: System Environment, Next: User Identification, Prev: Getting Out, Up: System Interface Operating System Environment ============================ Emacs 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. -- Variable: system-type The value of this variable is a symbol indicating the type of operating system Emacs is operating on. Here is a table of the symbols for the operating systems that Emacs can run on up to version 19.1. `aix-v3' AIX. `berkeley-unix' Berkeley BSD. `hpux' Hewlett-Packard operating system. `irix' Silicon Graphics Irix system. `linux' The free Linux operating system. `rtu' Masscomp RTU, UCB universe. `unisoft-unix' UniSoft UniPlus. `usg-unix-v' AT&T System V. `vax-vms' VAX VMS. `xenix' SCO Xenix 386. 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. -- Variable: 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 `string-match'. -- Function: system-name This function returns the name of the machine you are running on. (system-name) => "prep.ai.mit.edu" -- Function: getenv VAR This function returns the value of the environment variable VAR, as a string. Within Emacs, the environment variable values are kept in the Lisp variable `process-environment'. (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 -- Command: setenv VARIABLE VALUE 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. -- Variable: process-environment This variable is a list of strings, each describing one environment variable. The functions `getenv' and `setenv' work by means of 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") -- Variable: 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. -- Variable: invocation-directory This variable holds the directory from which the Emacs executable was invoked, or perhaps `nil' if that directory cannot be determined. -- Variable: installation-directory 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 near where the Emacs executable was found. -- Function: load-average This function returns the current 1 minute, 5 minute and 15 minute load averages in a list. The values are integers that are 100 times the system load averages. (The load averages indicate the number of processes trying to run.) (load-average) => (169 48 36) lewis@rocky[5] % uptime 11:55am up 1 day, 19:37, 3 users, load average: 1.69, 0.48, 0.36 -- Function: emacs-pid This function returns the process ID of the Emacs process. -- Function: setprv PRIVILEGE-NAME &optional SETP GETPRV This function sets or resets a VMS privilege. (It does not exist on Unix.) The first arg is the privilege name, as a string. The second argument, SETP, is `t' or `nil', indicating whether the privilege is to be turned on or off. Its default is `nil'. The function returns `t' if successful, `nil' otherwise. If the third argument, GETPRV, is non-`nil', `setprv' does not change the privilege, but returns `t' or `nil' indicating whether the privilege is currently enabled.  File: elisp, Node: User Identification, Next: Time of Day, Prev: System Environment, Up: System Interface User Identification =================== -- Function: user-login-name 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. (user-login-name) => "lewis" -- Function: user-real-login-name 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'. -- Function: user-full-name This function returns the full name of the user. (user-full-name) => "Bil Lewis" -- Function: user-real-uid This function returns the real UID of the user. (user-real-uid) => 19 -- Function: user-uid This function returns the effective UID of the user.  File: elisp, Node: Time of Day, Next: Timers, Prev: User Identification, Up: System Interface Time of Day =========== This section explains how to determine the current time and the time zone. -- Function: 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 `substring' to extract pieces of it. However, it would be 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 cons cell containing two integers, or a list whose first two elements are integers. Thus, you can use times obtained from `current-time' (see below) and from `file-attributes' (*note File Attributes::.). (current-time-string) => "Wed Oct 14 22:21:05 1987" -- Function: current-time 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 HIGH * 2**16 + LOW. 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'. *Note File Attributes::. -- Function: 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 `(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 integers, or a list whose first two elements are integers. Thus, you can use times obtained from `current-time' (see below) and from `file-attributes' (*note File Attributes::.).  File: elisp, Node: Timers, Next: Terminal Input, Prev: Time of Day, Up: System Interface Timers ====== You can set up a timer to call a function at a specified future time. -- Function: run-at-time TIME REPEAT FUNCTION &rest ARGS This function arranges to call FUNCTION with arguments ARGS at time TIME. The argument FUNCTION is a function to call later, and ARGS are the arguments to give it when it is called. The time TIME is specified as a string. Absolute times may be specified in a wide variety of formats; The form `HOUR:MIN:SEC TIMEZONE MONTH/DAY/YEAR', where all fields are numbers, works; the format that `current-time-string' returns is also allowed. To specify a relative time, use numbers followed by units. For example: `1 min' denotes 1 minute from now. `1 min 5 sec' denotes 65 seconds from now. `1 min 2 sec 3 hour 4 day 5 week 6 fortnight 7 month 8 year' denotes exactly 103 months, 123 days, and 10862 seconds from now. If TIME is an integer, that specifies a relative time measured in seconds. The argument REPEAT specifies how often to repeat the call. If REPEAT is `nil', there are no repetitions; FUNCTION is called just once, at TIME. If REPEAT is an integer, it specifies a repetition period measured in seconds. -- Function: cancel-timer TIMER Cancel the requested action for TIMER, which should be a value previously returned by `run-at-time'. This cancels the effect of that call to `run-at-time'; the arrival of the specified time will not cause anything special to happen.  File: elisp, Node: Terminal Input, Next: Terminal Output, Prev: Timers, Up: System Interface Terminal Input ============== This section describes functions and variables for recording or manipulating terminal input. See *Note 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.  File: elisp, Node: Input Modes, Next: Translating Input, Up: Terminal Input Input Modes ----------- -- Function: set-input-mode INTERRUPT FLOW META QUIT-CHAR This function sets the mode for reading keyboard input. If INTERRUPT is non-null, then Emacs uses input interrupts. If it is `nil', then it uses CBREAK mode. If FLOW is non-`nil', then Emacs uses XON/XOFF (`C-q', `C-s') flow control for output to terminal. This has no effect except in CBREAK mode. *Note 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', Emacs converts characters with the 8th bit set into Meta characters. If META is `nil', Emacs disregards the 8th bit; this is necessary when the terminal uses it as a parity bit. If META is neither `t' nor `nil', Emacs 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'. *Note Quitting::. The `current-input-mode' function returns the input mode settings Emacs is currently using. -- Function: current-input-mode 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: INTERRUPT is non-`nil' when Emacs is using interrupt-driven input. If `nil', Emacs is using CBREAK mode. FLOW is non-`nil' if Emacs uses XON/XOFF (`C-q', `C-s') flow control for output to the terminal. This value has no effect unless INTERRUPT is non-`nil'. META is non-`t' if Emacs treats the eighth bit of input characters as the meta bit; `nil' means Emacs clears the eighth bit of every input character; any other value means Emacs uses all eight bits as the basic character code. QUIT is the character Emacs currently uses for quitting, usually `C-g'. -- Variable: meta-flag This variable used to control whether to treat the eight bit in keyboard input characters as the Meta bit. `nil' meant no, and anything else meant yes. This variable existed in Emacs versions 18 and earlier but no longer exists in Emacs 19; use `set-input-mode' instead.