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This is Info file ../../info/lispref.info, produced by Makeinfo-1.63 from the input file lispref.texi. Edition History: GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994 XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995 GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp Programmer's Manual (for 19.13) Third Edition, July 1995 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc. Copyright (C) 1995 Amdahl Corporation. Copyright (C) 1995 Ben Wing. 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: lispref.info, Node: Filter Functions, Next: Accepting Output, Prev: Process Buffers, Up: Output from Processes Process Filter Functions ------------------------ A process "filter function" is a function that receives the standard output from the associated process. If a process has a filter, then *all* output from that process is passed to the filter. The process buffer is used directly for output from the process only when there is no filter. A filter function must accept two arguments: the associated process and a string, which is the output. The function is then free to do whatever it chooses with the output. A filter function runs only while XEmacs is waiting (e.g., for terminal input, or for time to elapse, or for process output). This avoids the timing errors that could result from running filters at random places in the middle of other Lisp programs. You may explicitly cause Emacs to wait, so that filter functions will run, by calling `sit-for' or `sleep-for' (*note Waiting::.), or `accept-process-output' (*note Accepting Output::.). Emacs is also waiting when the command loop is reading input. Quitting is normally inhibited within a filter function--otherwise, the effect of typing `C-g' at command level or to quit a user command would be unpredictable. If you want to permit quitting inside a filter function, bind `inhibit-quit' to `nil'. *Note Quitting::. If an error happens during execution of a filter function, it is caught automatically, so that it doesn't stop the execution of whatever program was running when the filter function was started. However, if `debug-on-error' is non-`nil', the error-catching is turned off. This makes it possible to use the Lisp debugger to debug the filter function. *Note Debugger::. Many filter functions sometimes or always insert the text in the process's buffer, mimicking the actions of XEmacs when there is no filter. Such filter functions need to use `set-buffer' in order to be sure to insert in that buffer. To avoid setting the current buffer semipermanently, these filter functions must use `unwind-protect' to make sure to restore the previous current buffer. They should also update the process marker, and in some cases update the value of point. Here is how to do these things: (defun ordinary-insertion-filter (proc string) (let ((old-buffer (current-buffer))) (unwind-protect (let (moving) (set-buffer (process-buffer proc)) (setq moving (= (point) (process-mark proc))) (save-excursion ;; Insert the text, moving the process-marker. (goto-char (process-mark proc)) (insert string) (set-marker (process-mark proc) (point))) (if moving (goto-char (process-mark proc)))) (set-buffer old-buffer)))) The reason to use an explicit `unwind-protect' rather than letting `save-excursion' restore the current buffer is so as to preserve the change in point made by `goto-char'. To make the filter force the process buffer to be visible whenever new text arrives, insert the following line just before the `unwind-protect': (display-buffer (process-buffer proc)) To force point to move to the end of the new output no matter where it was previously, eliminate the variable `moving' and call `goto-char' unconditionally. In earlier Emacs versions, every filter function that did regexp searching or matching had to explicitly save and restore the match data. Now Emacs does this automatically; filter functions never need to do it explicitly. *Note Match Data::. A filter function that writes the output into the buffer of the process should check whether the buffer is still alive. If it tries to insert into a dead buffer, it will get an error. If the buffer is dead, `(buffer-name (process-buffer PROCESS))' returns `nil'. The output to the function may come in chunks of any size. A program that produces the same output twice in a row may send it as one batch of 200 characters one time, and five batches of 40 characters the next. - Function: set-process-filter PROCESS FILTER This function gives PROCESS the filter function FILTER. If FILTER is `nil', then the process will have no filter. If FILTER is `t', then no output from the process will be accepted until the filter is changed. (Output received during this time is not discarded, but is queued, and will be processed as soon as the filter is changed.) - Function: process-filter PROCESS This function returns the filter function of PROCESS, or `nil' if it has none. `t' means that output processing has been stopped. Here is an example of use of a filter function: (defun keep-output (process output) (setq kept (cons output kept))) => keep-output (setq kept nil) => nil (set-process-filter (get-process "shell") 'keep-output) => keep-output (process-send-string "shell" "ls ~/other\n") => nil kept => ("lewis@slug[8] % " "FINAL-W87-SHORT.MSS backup.otl kolstad.mss~ address.txt backup.psf kolstad.psf backup.bib~ david.mss resume-Dec-86.mss~ backup.err david.psf resume-Dec.psf backup.mss dland syllabus.mss " "#backups.mss# backup.mss~ kolstad.mss ") File: lispref.info, Node: Accepting Output, Prev: Filter Functions, Up: Output from Processes Accepting Output from Processes ------------------------------- Output from asynchronous subprocesses normally arrives only while XEmacs is waiting for some sort of external event, such as elapsed time or terminal input. Occasionally it is useful in a Lisp program to explicitly permit output to arrive at a specific point, or even to wait until output arrives from a process. - Function: accept-process-output &optional PROCESS SECONDS MILLISEC This function allows XEmacs to read pending output from processes. The output is inserted in the associated buffers or given to their filter functions. If PROCESS is non-`nil' then this function does not return until some output has been received from PROCESS. The arguments SECONDS and MILLISEC let you specify timeout periods. The former specifies a period measured in seconds and the latter specifies one measured in milliseconds. The two time periods thus specified are added together, and `accept-process-output' returns after that much time whether or not there has been any subprocess output. Note that SECONDS is allowed to be a floating-point number; thus, there is no need to ever use MILLISEC. (It is retained for compatibility purposes.) The function `accept-process-output' returns non-`nil' if it did get some output, or `nil' if the timeout expired before output arrived. File: lispref.info, Node: Sentinels, Next: Process Window Size, Prev: Output from Processes, Up: Processes Sentinels: Detecting Process Status Changes =========================================== A "process sentinel" is a function that is called whenever the associated process changes status for any reason, including signals (whether sent by XEmacs or caused by the process's own actions) that terminate, stop, or continue the process. The process sentinel is also called if the process exits. The sentinel receives two arguments: the process for which the event occurred, and a string describing the type of event. The string describing the event looks like one of the following: * `"finished\n"'. * `"exited abnormally with code EXITCODE\n"'. * `"NAME-OF-SIGNAL\n"'. * `"NAME-OF-SIGNAL (core dumped)\n"'. A sentinel runs only while XEmacs is waiting (e.g., for terminal input, or for time to elapse, or for process output). This avoids the timing errors that could result from running them at random places in the middle of other Lisp programs. A program can wait, so that sentinels will run, by calling `sit-for' or `sleep-for' (*note Waiting::.), or `accept-process-output' (*note Accepting Output::.). Emacs is also waiting when the command loop is reading input. Quitting is normally inhibited within a sentinel--otherwise, the effect of typing `C-g' at command level or to quit a user command would be unpredictable. If you want to permit quitting inside a sentinel, bind `inhibit-quit' to `nil'. *Note Quitting::. A sentinel that writes the output into the buffer of the process should check whether the buffer is still alive. If it tries to insert into a dead buffer, it will get an error. If the buffer is dead, `(buffer-name (process-buffer PROCESS))' returns `nil'. If an error happens during execution of a sentinel, it is caught automatically, so that it doesn't stop the execution of whatever programs was running when the sentinel was started. However, if `debug-on-error' is non-`nil', the error-catching is turned off. This makes it possible to use the Lisp debugger to debug the sentinel. *Note Debugger::. In earlier Emacs versions, every sentinel that did regexp searching or matching had to explicitly save and restore the match data. Now Emacs does this automatically; sentinels never need to do it explicitly. *Note Match Data::. - Function: set-process-sentinel PROCESS SENTINEL This function associates SENTINEL with PROCESS. If SENTINEL is `nil', then the process will have no sentinel. The default behavior when there is no sentinel is to insert a message in the process's buffer when the process status changes. (defun msg-me (process event) (princ (format "Process: %s had the event `%s'" process event))) (set-process-sentinel (get-process "shell") 'msg-me) => msg-me (kill-process (get-process "shell")) -| Process: #<process shell> had the event `killed' => #<process shell> - Function: process-sentinel PROCESS This function returns the sentinel of PROCESS, or `nil' if it has none. - Function: waiting-for-user-input-p While a sentinel or filter function is running, this function returns non-`nil' if XEmacs was waiting for keyboard input from the user at the time the sentinel or filter function was called, `nil' if it was not. File: lispref.info, Node: Process Window Size, Next: Transaction Queues, Prev: Sentinels, Up: Processes Process Window Size =================== - Function: set-process-window-size PROCESS HEIGHT WIDTH This function tells PROCESS that its logical window size is HEIGHT by WIDTH characters. This is principally useful with pty's. File: lispref.info, Node: Transaction Queues, Next: Network, Prev: Process Window Size, Up: Processes Transaction Queues ================== You can use a "transaction queue" for more convenient communication with subprocesses using transactions. First use `tq-create' to create a transaction queue communicating with a specified process. Then you can call `tq-enqueue' to send a transaction. - Function: tq-create PROCESS This function creates and returns a transaction queue communicating with PROCESS. The argument PROCESS should be a subprocess capable of sending and receiving streams of bytes. It may be a child process, or it may be a TCP connection to a server, possibly on another machine. - Function: tq-enqueue QUEUE QUESTION REGEXP CLOSURE FN This function sends a transaction to queue QUEUE. Specifying the queue has the effect of specifying the subprocess to talk to. The argument QUESTION is the outgoing message that starts the transaction. The argument FN is the function to call when the corresponding answer comes back; it is called with two arguments: CLOSURE, and the answer received. The argument REGEXP is a regular expression that should match the entire answer, but nothing less; that's how `tq-enqueue' determines where the answer ends. The return value of `tq-enqueue' itself is not meaningful. - Function: tq-close QUEUE Shut down transaction queue QUEUE, waiting for all pending transactions to complete, and then terminate the connection or child process. Transaction queues are implemented by means of a filter function. *Note Filter Functions::. File: lispref.info, Node: Network, Prev: Transaction Queues, Up: Processes Network Connections =================== Emacs Lisp programs can open TCP network 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 XEmacs 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. It always returns either `open' or `closed' for a network connection, and it never returns either of those values for a real subprocess. *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 or IP address (a string), and SERVICE is the name of a defined network service (a string) or a port number (an integer). File: lispref.info, Node: System Interface, Next: X-Windows, 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 XEmacs::, for related information. See also *Note 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. File: lispref.info, Node: Starting Up, Next: Getting Out, Up: System Interface 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 (`.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: lispref.info, 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 XEmacs 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 processes the initial options. (Some of them are handled even earlier than this.) 3. It initializes the X window frame and faces, if appropriate. 4. It runs the normal hook `before-init-hook'. 5. It loads the library `site-start', unless the option `-no-site-file' was specified. The library's file name is usually `site-start.el'. 6. It loads the file `~/.emacs' unless `-q' was specified on the 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 `~'. 7. 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 the command line.) The library's file name is usually `default.el'. 8. It runs the normal hook `after-init-hook'. 9. It sets the major mode according to `initial-major-mode', provided the buffer `*scratch*' is still current and still in Fundamental mode. 10. It loads the terminal-specific Lisp file, if any, except when in batch mode or using a window system. 11. It displays the initial echo area message, unless you have suppressed that with `inhibit-startup-echo-area-message'. 12. It processes the action arguments from the command line. 13. It runs `term-setup-hook'. 14. It calls `frame-notice-user-settings', which modifies the parameters of the selected frame according to whatever the init files specify. 15. It runs `window-setup-hook'. *Note Terminal-Specific::. 16. 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: lispref.info, Node: Init File, Next: Terminal-Specific, Prev: Start-up Summary, Up: Starting Up The Init File: `.emacs' ----------------------- When you start XEmacs, it normally attempts to load the file `.emacs' from your home directory. This file, if it exists, must contain Lisp code. It is called your "init file". The command line switches `-q' and `-u' affect the use of the init file; `-q' says not to load an init file, and `-u' says to load a specified user's init file instead of yours. *Note Entering XEmacs: (emacs)Entering XEmacs. A site may have a "default init file", which is the library named `default.el'. XEmacs finds the `default.el' file through the standard search path for libraries (*note How Programs Do Loading::.). The XEmacs distribution does not come with this file; sites may provide one for local customizations. If the default init file exists, it is loaded whenever you start Emacs, except in batch mode or if `-q' is specified. But your own personal init file, if any, is loaded first; if it sets `inhibit-default-init' to a non-`nil' value, then XEmacs does not subsequently load the `default.el' file. Another file for site-customization is `site-start.el'. Emacs loads this *before* the user's init file. You can inhibit the loading of this file with the option `-no-site-file'. - Variable: site-run-file This variable specifies the site-customization file to load before the user's init file. Its normal value is `"site-start"'. If there is a great deal of code in your `.emacs' file, you should move it into another file named `SOMETHING.el', byte-compile it (*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 XEmacs from loading the default initialization library file for your session of XEmacs. If its value is non-`nil', then the default library is not loaded. The default value is `nil'. - 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: lispref.info, 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 XEmacs loads when run on that type of terminal. For a terminal type named TERMTYPE, the library is called `term/TERMTYPE'. XEmacs finds the file by searching the `load-path' directories as it does for other files, and trying the `.elc' and `.el' suffixes. Normally, terminal-specific Lisp library is located in `emacs/lisp/term', a subdirectory of the `emacs/lisp' directory in which most 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 XEmacs can recognize. It may also need to set or add to `function-key-map' if the Termcap entry does not specify all the terminal's function keys. *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 XEmacs runs using `run-hooks' at the end of XEmacs initialization, after loading both your `.emacs' file and any terminal-specific libraries. You can use this variable to define initializations for terminals that do not have their own libraries. *Note Hooks::. - Variable: term-file-prefix If the `term-file-prefix' variable is non-`nil', XEmacs loads a terminal-specific initialization file as follows: (load (concat term-file-prefix (getenv "TERM"))) You may set the `term-file-prefix' variable to `nil' in your `.emacs' file if you do not wish to load the terminal-initialization file. To do this, put the following in your `.emacs' file: `(setq term-file-prefix nil)'. - Variable: term-setup-hook This variable is a normal hook that XEmacs runs after loading your `.emacs' file, the default initialization file (if any) and the terminal-specific Lisp file. You can use `term-setup-hook' to override the definitions made by a terminal-specific file. - Variable: window-setup-hook This variable is a normal hook which XEmacs runs after loading your `.emacs' file and the default initialization file (if any), after loading terminal-specific Lisp code, and after running the hook `term-setup-hook'. File: lispref.info, 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 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. - Function: command-line This function parses the command line that XEmacs was called with, processes it, loads the user's `.emacs' file and displays the startup messages. - Variable: command-line-processed The value of this variable is `t' once the command line has been processed. If you redump XEmacs by calling `dump-emacs', you may wish to set this variable to `nil' first in order to cause the new dumped XEmacs to process its new command line arguments. - 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 XEmacs. - 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 order of appearance, until one of them returns a non-`nil' value. These functions are called with no arguments. They can access the command-line argument under consideration through the variable `argi'. The remaining arguments (not including the current one) are in the variable `command-line-args-left'. When a function recognizes and processes the argument in `argi', it should return a non-`nil' value to say it has dealt with that argument. If it has also dealt with some of the following arguments, it can indicate that by deleting them from `command-line-args-left'. If all of these functions return `nil', then the argument is used as a file name to visit. File: lispref.info, Node: Getting Out, Next: System Environment, Prev: Starting Up, Up: System Interface Getting out of 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. File: lispref.info, Node: Killing XEmacs, Next: Suspending XEmacs, Up: Getting Out 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 `kill-emacs'. - Function: kill-emacs &optional EXIT-DATA This function exits the XEmacs process and kills it. If 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 *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 XEmacs process, aside from files that have been saved, is lost when the XEmacs is killed. Because killing XEmacs inadvertently can lose a lot of work, XEmacs queries for confirmation before actually terminating if you have buffers that need saving or subprocesses that are running. This is done in the function `save-buffers-kill-emacs'. - 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', XEmacs 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: lispref.info, Node: Suspending XEmacs, Prev: Killing XEmacs, Up: Getting Out Suspending XEmacs ----------------- "Suspending XEmacs" means stopping XEmacs temporarily and returning control to its superior process, which is usually the shell. This allows you to resume editing later in the same XEmacs process, with the same buffers, the same kill ring, the same undo history, and so on. To resume XEmacs, use the appropriate command in the parent shell--most likely `fg'. Some operating systems do not support suspension of jobs; on these systems, "suspension" actually creates a new shell temporarily as a subprocess of XEmacs. Then you would exit the shell to return to XEmacs. Suspension is not useful with window systems such as X, because the XEmacs job may not have a parent that can resume it again, and in any case you can give input to some other job such as a shell merely by moving to a different window. Therefore, suspending is not allowed when XEmacs is an X client. - Function: suspend-emacs STRING This function stops XEmacs and returns control to the superior process. If and when the superior process resumes XEmacs, `suspend-emacs' returns `nil' to its caller in Lisp. If STRING is non-`nil', its characters are sent to be read as terminal input by XEmacs'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 XEmacs, `suspend-emacs' 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 XEmacs is suspended. But it is read and executed by the shell. (suspend-emacs) => nil (add-hook 'suspend-hook (function (lambda () (or (y-or-n-p "Really suspend? ") (error "Suspend cancelled"))))) => (lambda nil (or (y-or-n-p "Really suspend? ") (error "Suspend cancelled"))) (add-hook 'suspend-resume-hook (function (lambda () (message "Resumed!")))) => (lambda nil (message "Resumed!")) (suspend-emacs "pwd") => nil ---------- Buffer: Minibuffer ---------- Really suspend? `y' ---------- Buffer: Minibuffer ---------- ---------- Parent Shell ---------- lewis@slug[23] % /user/lewis/manual lewis@slug[24] % fg ---------- Echo Area ---------- Resumed! - 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: lispref.info, Node: System Environment, Next: User Identification, Prev: Getting Out, Up: System Interface 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 UID, and so on. - Variable: 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: `aix-v3' AIX. `berkeley-unix' Berkeley BSD. `dgux' Data General DGUX operating system. `gnu' A GNU system using the GNU HURD and Mach. `hpux' Hewlett-Packard HPUX operating system. `irix' Silicon Graphics Irix system. `linux' A GNU system using the Linux kernel. `ms-dos' Microsoft MS-DOS "operating system." `next-mach' NeXT Mach-based system. `rtu' Masscomp RTU, UCB universe. `unisoft-unix' UniSoft UniPlus. `usg-unix-v' AT&T System V. `vax-vms' VAX VMS. `windows-nt' Microsoft windows NT. `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" The symbol `system-name' is a variable as well as a function. In fact, the function returns whatever value the variable `system-name' currently holds. Thus, you can set the variable `system-name' in case Emacs is confused about the name of your system. The variable is also useful for constructing frame titles (*note Frame Titles::.). - Variable: mail-host-address If this variable is non-`nil', it is used instead of `system-name' for purposes of generating email addresses. For example, it is used when constructing the default value of `user-mail-address'. *Note User Identification::. (Since this is done when XEmacs starts up, the value actually used is the one saved when XEmacs was dumped. *Note Building XEmacs::.) - Function: getenv VAR This function returns the value of the environment variable VAR, as a string. Within XEmacs, the environment variable values are kept in the Lisp variable `process-environment'. (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: 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 `":"' for Unix and GNU systems, and `";"' for MS-DOS and Windows NT. - 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 in a directory related somehow to the one containing the Emacs executable. - 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: lispref.info, Node: User Identification, Next: Time of Day, Prev: System Environment, Up: System Interface User Identification =================== - Variable: 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. - Function: user-login-name &optional UID If you don't specify UID, this function returns the name under which the user is logged in. If the environment variable `LOGNAME' is set, that value is used. Otherwise, if the environment variable `USER' is set, that value is used. Otherwise, the value is based on the effective UID, not the real UID. If you specify UID, the value is the user name that corresponds to UID (which should be an integer). (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" The symbols `user-login-name', `user-real-login-name' and `user-full-name' are variables as well as functions. The functions return the same values that the variables hold. These variables allow you to "fake out" Emacs by telling the functions what to return. The variables are also useful for constructing frame titles (*note Frame Titles::.). - 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: lispref.info, Node: Time of Day, Next: Time Conversion, 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. It is wise to count the characters from the beginning of the string rather than from the end, as additional information may be added at the end. The argument TIME-VALUE, if given, specifies a time to format instead of the current time. The argument should be a list whose first two elements are 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 above) and from `file-attributes' (*note File Attributes::.).