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Info file elisp, produced by Makeinfo, -*- Text -*- from input file elisp.texi. This file documents GNU Emacs Lisp. This is edition 1.03 of the GNU Emacs Lisp Reference Manual, for Emacs Version 18. Published by the Free Software Foundation, 675 Massachusetts Avenue, Cambridge, MA 02139 USA Copyright (C) 1990 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. File: elisp, Node: Deleting Processes, Next: Process Information, Prev: Asynchronous Processes, Up: Processes Deleting Processes ================== "Deleting a process" disconnects Emacs immediately from the subprocess, and removes it from the list of active processes. It sends a signal to the subprocess to make the subprocess terminate, but this is not guaranteed to happen immediately. (The process object itself continues to exist as long as other Lisp objects point to it.) You can delete a process explicitly at any time. Processes are deleted automatically after they terminate, but not necessarily right away. If you delete a terminated process explicitly before it is deleted automatically, no harm results. * Variable: delete-exited-processes This variable controls automatic deletion of processes that have terminated (due to calling `exit' or to a signal). If it is `nil', then they continue to exist until the user runs `list-processes'. Otherwise, they are deleted immediately after they exit. * Function: delete-process NAME This function deletes the process associated with NAME. The argument NAME may be a process, the name of a process, a buffer, or the name of a buffer. The subprocess is killed with a `SIGHUP' signal. (delete-process "*shell*") => nil * Function: process-kill-without-query PROCESS This function declares that Emacs need not query the user if PROCESS is still running when Emacs is exited. The process will be deleted silently. The value is `t'. (process-kill-without-query (get-process "shell")) => t File: elisp, Node: Process Information, Next: Input to Processes, Prev: Deleting Processes, Up: Processes Process Information =================== Several functions return information about processes. `list-processes' is provided for interactive use. * Command: list-processes This command displays a listing of all living processes. (Any processes listed as `Exited' or `Signaled' are actually eliminated after the listing is made.) This function returns `nil'. * Function: process-list This function returns a list of all processes that have not been deleted. (process-list) => (#<process display-time> #<process shell>) * Function: get-process NAME This function returns the process named NAME, or `nil' if there is none. An error is signaled if NAME is not a string. (get-process "shell") => #<process shell> * Function: process-command PROCESS This function returns the command that was executed to start PROCESS. This is a list of strings, the first string being the program executed and the rest of the strings being the arguments that were given to the program. (process-command (get-process "shell")) => ("/bin/csh" "-i") * Function: process-exit-status PROCESS This function returns the exit status of PROCESS or the signal number that killed it. If PROCESS has not yet terminated, the value is 0. * Function: process-id PROCESS This function returns the PID of PROCESS. This is an integer which distinguishes the process PROCESS from all other processes running on the same computer at the current time. The PID of a process is chosen by the operating system kernel when the process is started and remains constant as long as the process exists. * Function: process-name PROCESS This function returns the name of PROCESS. * Function: process-status PROCESS-NAME This function returns the status of PROCESS-NAME as a symbol. The argument PROCESS-NAME must be either a process or a string. If it is a string, it need not name an actual process. The possible values for an actual subprocess are: `run' for a process that is running. `stop' for a process that is stopped but continuable. `exit' for a process that has exited. `signal' for a process that has received a fatal signal. `nil' if PROCESS-NAME is not the name of an existing process. (process-status "shell") => run (process-status "never-existed") => nil x => #<process xx<1>> (process-status x) => exit For a network stream, `process-status' returns one of the symbols `open' or `closed'. The latter means that the other side closed the connection, or Emacs did `delete-process'. File: elisp, Node: Input to Processes, Next: Signals to Processes, Prev: Process Information, Up: Processes Sending Input to Processes ========================== Asynchronous subprocesses receive input when it is sent to them by Emacs, which is done with the functions in this section. You must specify the process to send input to, and the input data to send. The data appears on the "standard input" of the subprocess. Some operating systems have limited space for buffered input in a PTY. On these systems, the subprocess will cease to read input correctly if you send an input line longer than the system can handle. You cannot avoid the problem by breaking the input into pieces and sending them separately, for the operating system will still have to put all the pieces together in the input buffer before it lets the subprocess read the line. The only solution is to put the input in a temporary file, and send the process a brief command to read that file. * Function: process-send-string PROCESS-NAME STRING This function sends PROCESS-NAME the contents of STRING as standard input. The argument PROCESS-NAME must be a process or the name of a process. The function returns `nil'. (process-send-string "shell<1>" "ls\n") => nil ---------- Buffer: *shell* ---------- ... introduction.texi syntax-tables.texi~ introduction.texi~ text.texi introduction.txt text.texi~ ... ---------- Buffer: *shell* ---------- * Command: process-send-region PROCESS-NAME START END This function sends the text in the region defined by START and END as standard input to PROCESS-NAME, which is a process or a process name. An error is signaled unless both START and END are integers or markers that indicate positions in the current buffer. (It is unimportant which number is larger.) * Function: process-send-eof &optional PROCESS-NAME This function makes PROCESS-NAME see an end-of-file in its input. The EOF comes after any text already sent to it. If PROCESS-NAME is not supplied, or if it is `nil', then this function sends the EOF to the current buffer's process. An error is signaled if the current buffer has no process. The function returns PROCESS-NAME. (process-send-eof "shell") => "shell" File: elisp, Node: Signals to Processes, Next: Output from Processes, Prev: Input to Processes, Up: Processes Sending Signals to Processes ============================ "Sending a signal" to a subprocess is a way of interrupting its activities. There are several different signals, each with its own meaning. For example, the signal `SIGINT' means that the user has typed `C-c', or that some analogous thing has happened. Each signal has a standard effect on the subprocess. Most signals kill the subprocess, but some stop or resume execution instead. Most signals can optionally be handled by programs; if the program handles the signal, then we can say nothing in general about its effects. The set of signals and their names is defined by the operating system; Emacs has facilities for sending only a few of the signals that are defined. Emacs can send signals only to its own subprocesses. You can send signals explicitly by calling the function in this section. Emacs also sends signals automatically at certain times: killing a buffer sends a `SIGHUP' signal to all its associated processes; killing Emacs sends a `SIGHUP' signal to all remaining processes. (`SIGHUP' is a signal that usually indicates that the user hung up the phone.) Each of the signal-sending functions takes two optional arguments: PROCESS-NAME and CURRENT-GROUP. The argument PROCESS-NAME must be either a process, the name of one, or `nil'. If it is `nil', the process defaults to the process associated with the current buffer. An error is signaled if PROCESS-NAME does not identify a process. The argument CURRENT-GROUP is a flag that makes a difference when you are running a job-control shell as an Emacs subprocess. If it is non-`nil', then the signal is sent to the current process-group of the terminal which Emacs uses to communicate with the subprocess. If the process is a job-control shell, this means the shell's current subjob. If it is `nil', the signal is sent to the process group of the immediate subprocess of Emacs. If the subprocess is a job-control shell, this is the shell itself. The flag CURRENT-GROUP has no effect when a pipe is used to communicate with the subprocess, because the operating system does not support the distinction in the case of pipes. For the same reason, job-control shells won't work when a pipe is used. See `process-connection-type' in *Note Asynchronous Processes::. * Function: interrupt-process &optional PROCESS-NAME CURRENT-GROUP This function interrupts the process PROCESS-NAME by sending the Unix signal `SIGINT'. Outside of Emacs, typing the "interrupt character" (usually `C-c' on Berkeley Unix) sends this signal. When the argument CURRENT-GROUP is non-`nil', you can think of this function as "typing `C-c'" on the terminal by which Emacs talks to the subprocess. * Function: kill-process &optional PROCESS-NAME CURRENT-GROUP This function kills the process PROCESS-NAME by sending the Unix signal `SIGKILL'. This signal kills the subprocess immediately, and cannot be handled by the subprocess. * Function: quit-process &optional PROCESS-NAME CURRENT-GROUP This function sends the Unix signal `SIGQUIT' to the process PROCESS-NAME. This signal is the one sent by the "quit character" (usually `C-b' or `C-\') when you are not inside Emacs. * Function: stop-process &optional PROCESS-NAME CURRENT-GROUP This function stops the process PROCESS-NAME by sending the Unix signal `SIGTSTP'. Use `continue-process' to resume its execution. On systems with job control, the "stop character" (usually `C-z') sends this signal (outside of Emacs). When CURRENT-GROUP is non-`nil', you can think of this function as "typing `C-z'" on the terminal Emacs uses to communicate with the subprocess. * Function: continue-process &optional PROCESS-NAME CURRENT-GROUP This function resumes execution of the process PROCESS by sending it the Unix signal `SIGCONT'. This presumes that PROCESS-NAME was stopped previously. File: elisp, Node: Output from Processes, Next: Sentinels, Prev: Signals to Processes, Up: Processes Receiving Output from Processes =============================== There are two ways to receive the output that a subprocess writes to its standard output stream. The output can be inserted in a buffer, which is called the associated buffer of the process, or a function called the "filter function" can be called to act on the output. * Menu: * Process Buffers:: If no filter, output is put in a buffer. * Filter Functions:: Filter functions accept output from the process. * Accepting Output:: Explicitly permitting subprocess output. Waiting for subprocess output. File: elisp, Node: Process Buffers, Next: Filter Functions, Prev: Output from Processes, Up: Output from Processes Process Buffers --------------- A process can (and usually does) have an "associated buffer", which is an ordinary Emacs buffer that is used for two purposes: storing the output from the process, and deciding when to kill the process. You can also use the buffer to identify a process to operate on, since in normal practice only one process is associated with any given buffer. Many applications of processes also use the buffer for editing input to be sent to the process, but this is not built into Emacs Lisp. Unless the process has a filter function (*note Filter Functions::.), its output is inserted in the associated buffer. The position to insert the output is determined by the `process-mark' (*note Process Information::.), which is then updated to point to the end of the text just inserted. Usually, but not always, the `process-mark' is at the end of the buffer. If the process has no buffer and no filter function, its output is discarded. * Function: process-buffer PROCESS This function returns the associated buffer of the process PROCESS. (process-buffer (get-process "shell")) => #<buffer *shell*> * Function: process-mark PROCESS This function returns the marker which controls where additional output from the process will be inserted in the process buffer (*note Process Buffers::.). When output is inserted, the marker is updated to point at the end of the output. This causes successive batches of output to be inserted consecutively. If PROCESS does not insert its output into a buffer, then `process-mark' returns a marker that points nowhere. Filter functions normally should use this marker in the same fashion as is done by direct insertion of output in the buffer. A good example of a filter function that uses `process-mark' is found at the end of the following section. When the user is expected to enter input in the process buffer for transmission to the process, the process marker is useful for distinguishing the new input from previous output. * Function: set-process-buffer PROCESS BUFFER This function sets the buffer associated with PROCESS to BUFFER. If BUFFER is `nil', the process will not be associated with any buffer. * Function: get-buffer-process BUFFER-OR-NAME This function returns the process associated with BUFFER-OR-NAME. If there are several processes associated with it, then one is chosen. (Presently, the one chosen is the one most recently created.) It is usually a bad idea to have more than one process associated with the same buffer. (get-buffer-process "*shell*") => #<process shell> If the process's buffer is killed, the actual child process is killed with a `SIGHUP' signal (*note Signals to Processes::.). File: elisp, 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* standard output from that process is passed to the filter rather than be inserted into a buffer or discarded. The process buffer is used 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 Emacs 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', `sleep-for' 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::. Many filter functions sometimes or always insert the text in the process's buffer, mimicking the actions of Emacs 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. All filter functions that do regexp searching or matching should save and restore the match data. Otherwise, a filter function that runs during a call to `sit-for' might clobber the match data of the program that called `sit-for'. *Note Match Data::. 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. * Function: process-filter PROCESS This function returns the filter function of PROCESS, or `nil' if it has none. 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 ") Here is another, more realistic example, which demonstrates how to use the process mark to do insertion in the same fashion as is done when there is no filter function: ;; Insert input in the buffer specified by `my-shell-buffer' ;; and make sure that buffer is shown in some window. (defun my-process-filter (proc str) (let ((cur (selected-window)) (pop-up-windows t)) (pop-to-buffer my-shell-buffer) (goto-char (point-max)) (insert str) (set-marker (process-mark proc) (point-max)) (select-window cur))) File: elisp, Node: Accepting Output, Prev: Filter Functions, Up: Output from Processes Accepting Output from Processes ------------------------------- Output from asynchronous subprocesses normally arrives only while Emacs 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 This function allows Emacs 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. File: elisp, Node: Sentinels, Next: VMS Subprocesses, 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 Emacs 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 Emacs 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. You may explicitly cause Emacs to wait, so that sentinels will run, by calling `sit-for', `sleep-for' 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::. All sentinels that do regexp searching or matching should save and restore the match data. Otherwise, a sentinel that runs during a call to `sit-for' might clobber the match data of the program that called `sit-for'. *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 Emacs was waiting for keyboard input from the user at the time the sentinel or filter function was called, `nil' if it was not. File: elisp, Node: VMS Subprocesses, Next: TCP, Prev: Sentinels, Up: Processes Subprocess Functions for VMS ============================ The ordinary subprocess functions do not work on VMS in version 18. Instead, these functions are available. * Function: default-subprocess-input-handler This function is the default input handler for input from spawned subprocesses. * Function: spawn-subprocess INTEGER &optional FILTER SENTINEL This function spawns an asynchronous VMS subprocess for command processing. The arguments are INTEGER, an integer to identify the subprocess in future operations; FILTER, a function to be called when output arrives from the subprocess; and SENTINEL, a function to be called when the subprocess terminates. If FILTER is `nil', output is inserted in the current buffer. If SENTINEL is `nil', nothing special is done when the subprocess terminates. When the filter is called, it receives two arguments; INTEGER to identify the process, and a string containing the output. When the sentinel is called, it receives just one argument, INTEGER. * Function: send-command-to-subprocess INTEGER COMMAND This function sends the string COMMAND to a VMS subprocess numbered INTEGER. * Function: stop-subprocess INTEGER This function terminates the VMS subprocess numbered INTEGER. In version 19, these functions have been eliminated, and the ordinary subprocess functions are implemented on VMS. File: elisp, Node: TCP, Prev: VMS Subprocesses, 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 of it. You can distinguish process objects representing network connections from those representing subprocesses with the `process-status' function. * 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 the service desired (a string) or an integer specifying a port number to connect to. File: elisp, Node: System Interface, Next: Emacs 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 Emacs Display::, for additional operating system status information which pertain 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. * 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 Emacs without terminal interaction. File: elisp, Node: Starting Up, Next: Getting Out, Prev: System Interface, 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, Prev: Starting Up, 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 `.emacs' unless `-q' was specified on command line. (This is not done in `-batch' mode.) `.emacs' is found in the user's home directory; the `-u' option can specify the user name whose home directory should be used. 2. It loads `default.el' unless `inhibit-default-init' is non-`nil'. (This is not done in `-batch' mode or if `-q' was specified on command line.) 3. It loads the terminal-specific Lisp file, if any, except when in batch mode. 4. It runs `term-setup-hook'. 5. It runs `window-setup-hook'. 6. It displays copyleft and nonwarranty, plus basic use information, unless the value of `inhibit-startup-message' is non-`nil'. This display is also inhibited in batch mode, and if the current buffer is not `*scratch*'. 7. It processes any remaining command line arguments. * 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. 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' can be used to control 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 : (emacs)Entering Emacs. Emacs may also 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 have any such file; you may create one at your site 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 will not load the `default.el' 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 : (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'. 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 will load 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 purpose of a terminal-specific library is to define the escape sequences used by a terminal's function keys. See the file `term/vt100.el' for an example of a terminal-specific library. Function keys are handled by a two-level procedure. The first level is dependent on the specific type of terminal and maps Emacs's input sequences to the function keys that they represent. The second level is independent of terminal type and is customized by users; function keys are mapped into meanings at this level. The terminal-specific library handles the first level of the process and the library `keypad.el' handles the second level of mapping. 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 `term-file-prefix' to `nil'. This feature is very 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'. If it is not `nil', Emacs calls the value of the variable `term-setup-hook' as a function of no arguments at the end of Emacs initialization, after Emacs has already loaded 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. * 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 The value of this variable is either `nil' or a function to be called by Emacs after loading your `.emacs' file, the default initialization file (if any) and after loading terminal-specific Lisp code. The function is called with no arguments. You can use `term-setup-hook' to override the definitions made by a terminal-specific file. See also `window-setup-hook' in *Note Window Systems::. 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. * 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 must 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) For each element, the HANDLER-FUNCTION receives the switch 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 : (emacs)Command Switches. * Variable: command-line-args The value of this variable is the arguments passed by the shell to Emacs, as a list of strings. 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, Prev: Getting Out, Up: Getting Out Killing Emacs ------------- Killing Emacs means ending the execution of the Emacs process. It will return to its superior process. 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 will query for confirmation before actually terminating if you have buffers that need saving or subprocesses that are running. * Function: kill-emacs &optional NO-QUERY This function exits the Emacs process and kills it. Normally, if there are modified files or if there are running processes, `kill-emacs' asks the user for confirmation before exiting. However, if NO-QUERY is supplied and non-`nil', then Emacs exits without confirmation. If NO-QUERY 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 NO-QUERY 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. * Variable: kill-emacs-hook The value of the `kill-emacs-hook' variable is either `nil' or is that of a function to be called by `kill-emacs'. The hook is called before anything else is done by `kill-emacs'. 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 Windows, 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 under X Windows. * Function: suspend-emacs STRING This function stops Emacs and returns to the superior process. It returns `nil'. If STRING is non-`nil', its characters are sent to be read as terminal input by Emacs's superior shell. The characters in STRING will not be echoed by the superior shell; just the results will appear. Before suspending, Emacs examines the symbol `suspend-hook'. If it is bound, and its value is non-`nil', then the value is called as a function of no arguments. If the function returns non-`nil', then `suspend-emacs' returns immediately and suspension does not occur. After Emacs resumes, the symbol `suspend-resume-hook' is examined. If it is bound and non-`nil', then the value is called as a function of no arguments. The next redisplay after resumption will redraw the entire screen, unless `no-redraw-on-reenter' is set (*note Screen Attributes::.). 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 (setq suspend-hook (function (lambda () (not (y-or-n-p "Really suspend? "))))) => (lambda nil (not (y-or-n-p "Really suspend? "))) (setq suspend-resume-hook (function (lambda () (message "Resumed!")))) => (lambda nil (message "Resumed!")) (suspend-emacs "pwd") => nil ---------- Buffer: Minibuffer ---------- Really suspend? `y' ---------- Parent Shell ---------- lewis@slug[23] % /user/lewis/manual lewis@slug[24] % fg ---------- Echo Area ---------- Resumed! * Variable: suspend-hook The value of the `suspend-hook' variable, if not `nil', is called as a function with no arguments by `suspend-emacs' before Emacs is actually suspended. If the function returns non-`nil', then suspension does not take place. * Variable: suspend-resume-hook The value of the `suspend-resume-hook' variable, if not `nil', is called as a function with no arguments after resumption of an Emacs session that was suspended with `suspend-emacs'. File: elisp, Node: System Environment, Next: Terminal Input, 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 18.51. `berkeley-unix' Berkeley BSD 4.1, 4.2, or 4.3. `hpux' Hewlett-Packard operating system, version 5, 6, or 7. `silicon-graphics-unix' Silicon Graphics Iris 3.5 or 3.6. `rtu' RTU 3.0, UCB universe. `unisoft-unix' UniSoft's UniPlus 5.0 or 5.2. `usg-unix-v' AT&T's System V.0, System V Release 2.0, 2.2, or 3. `vax-vms' VMS VMS version 4 or 5. `xenix' SCO Xenix 386 Release 2.2. We do not wish to add new symbols to make finer distinctions unless it is absolutely necessary! In fact, it would be nice to eliminate a couple of possibilities in the future. * Function: getenv VAR This function returns the value of the environment variable VAR, as a string. (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 * Function: user-login-name This function returns the name under which the user is logged in. This is based on the effective UID, not the real UID. (user-login-name) => "lewis" * Function: user-real-login-name This function returns the name under which the user logged in. This is based on the real UID, not the effective UID. This differs from `user-login-name' only when running with the setuid bit. * 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. * Function: system-name This function returns the name of the machine you are running on. (system-name) => "prep.ai.mit.edu" * Function: current-time-string 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 describing the time zone may be added in version 19. (current-time-string) => "Wed Oct 14 22:21:05 1987" * 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: 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 success, `nil' if not. 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.