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This is Info file elisp, produced by Makeinfo-1.55 from the input file elisp.texi. This is edition 2.0 of the GNU Emacs Lisp Reference Manual, for Emacs Version 19. Published by the Free Software Foundation, 675 Massachusetts Avenue, Cambridge, MA 02139 USA Copyright (C) 1990, 1991, 1992, 1993 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: Abbrev Tables, Next: Defining Abbrevs, Prev: Abbrev Mode, Up: Abbrevs Abbrev Tables ============= This section describes how to create and manipulate abbrev tables. - Function: make-abbrev-table This function creates and returns a new, empty abbrev table--an obarray containing no symbols. It is a vector filled with `nil's. - Function: clear-abbrev-table TABLE This function undefines all the abbrevs in abbrev table TABLE, leaving it empty. The function returns `nil'. - Function: define-abbrev-table TABNAME DEFINITIONS This function defines TABNAME (a symbol) as an abbrev table name, i.e., as a variable whose value is an abbrev table. It defines abbrevs in the table according to DEFINITIONS, a list of elements of the form `(ABBREVNAME EXPANSION HOOK USECOUNT)'. The value is always `nil'. - Variable: abbrev-table-name-list This is a list of symbols whose values are abbrev tables. `define-abbrev-table' adds the new abbrev table name to this list. - Function: insert-abbrev-table-description NAME &optional HUMAN This function inserts before point a description of the abbrev table named NAME. The argument NAME is a symbol whose value is an abbrev table. The value is always `nil'. If HUMAN is non-`nil', a human-oriented description is inserted. Otherwise the description is a Lisp expression--a call to `define-abbrev-table' which would define NAME exactly as it is currently defined. File: elisp, Node: Defining Abbrevs, Next: Abbrev Files, Prev: Abbrev Tables, Up: Abbrevs Defining Abbrevs ================ These functions define an abbrev in a specified abbrev table. `define-abbrev' is the low-level basic function, while `add-abbrev' is used by commands that ask for information from the user. - Function: add-abbrev TABLE TYPE ARG This function adds an abbreviation to abbrev table TABLE. The argument TYPE is a string describing in English the kind of abbrev this will be (typically, `"global"' or `"mode-specific"'); this is used in prompting the user. The argument ARG is the number of words in the expansion. The return value is the symbol which internally represents the new abbrev, or `nil' if the user declines to redefine an existing abbrev. - Function: define-abbrev TABLE NAME EXPANSION HOOK This function defines an abbrev in TABLE named NAME, to expand to EXPANSION, and call HOOK. The return value is an uninterned symbol which represents the abbrev inside Emacs; its name is NAME. The argument NAME should be a string. The argument EXPANSION should be a string, or `nil', to undefine the abbrev. The argument HOOK is a function or `nil'. If HOOK is non-`nil', then it is called with no arguments after the abbrev is replaced with EXPANSION; point is located at the end of EXPANSION. The use count of the abbrev is initialized to zero. - User Option: only-global-abbrevs If this variable is non-`nil', it means that the user plans to use global abbrevs only. This tells the commands that define mode-specific abbrevs to define global ones instead. This variable does not alter the functioning of the functions in this section; it is examined by their callers. File: elisp, Node: Abbrev Files, Next: Abbrev Expansion, Prev: Defining Abbrevs, Up: Abbrevs Saving Abbrevs in Files ======================= A file of saved abbrev definitions is actually a file of Lisp code. The abbrevs are saved in the form of a Lisp program to define the same abbrev tables with the same contents. Therefore, you can load the file with `load' (*note How Programs Do Loading::.). However, the function `quietly-read-abbrev-file' is provided as a more convenient interface. User-level facilities such as `save-some-buffers' can save abbrevs in a file automatically, under the control of variables described here. - User Option: abbrev-file-name This is the default file name for reading and saving abbrevs. - Function: quietly-read-abbrev-file FILENAME This function reads abbrev definitions from a file named FILENAME, previously written with `write-abbrev-file'. If FILENAME is `nil', the file specified in `abbrev-file-name' is used. `save-abbrevs' is set to `t' so that changes will be saved. This function does not display any messages. It returns `nil'. - User Option: save-abbrevs A non-`nil' value for `save-abbrev' means that Emacs should save abbrevs when files are saved. `abbrev-file-name' specifies the file to save the abbrevs in. - Variable: abbrevs-changed This variable is set non-`nil' by defining or altering any abbrevs. This serves as a flag for various Emacs commands to offer to save your abbrevs. - Command: write-abbrev-file FILENAME Save all abbrev definitions, in all abbrev tables, in the file FILENAME, in the form of a Lisp program which when loaded will define the same abbrevs. This function returns `nil'. File: elisp, Node: Abbrev Expansion, Next: Standard Abbrev Tables, Prev: Abbrev Files, Up: Abbrevs Looking Up and Expanding Abbreviations ====================================== Abbrevs are usually expanded by commands for interactive use, including `self-insert-command'. This section describes the subroutines used in writing such functions, as well as the variables they use for communication. - Function: abbrev-symbol ABBREV &optional TABLE This function returns the symbol representing the abbrev named ABBREV. The value returned is `nil' if that abbrev is not defined. The optional second argument TABLE is the abbrev table to look it up in. By default, this function tries first the current buffer's local abbrev table, and second the global abbrev table. - User Option: abbrev-all-caps When this is set non-`nil', an abbrev entered entirely in upper case is expanded using all upper case. Otherwise, an abbrev entered entirely in upper case is expanded by capitalizing each word of the expansion. - Function: abbrev-expansion ABBREV &optional TABLE This function returns the string that ABBREV would expand into (as defined by the abbrev tables used for the current buffer). The optional argument TABLE specifies the abbrev table to use; if it is specified, the abbrev is looked up in that table only. - Variable: abbrev-start-location This is the buffer position for `expand-abbrev' to use as the start of the next abbrev to be expanded. (`nil' means use the word before point instead.) `abbrev-start-location' is set to `nil' each time `expand-abbrev' is called. This variable is also set by `abbrev-prefix-mark'. - Variable: abbrev-start-location-buffer The value of this variable is the buffer for which `abbrev-start-location' has been set. Trying to expand an abbrev in any other buffer clears `abbrev-start-location'. This variable is set by `abbrev-prefix-mark'. - Variable: last-abbrev This is the `abbrev-symbol' of the last abbrev expanded. This information is left by `expand-abbrev' for the sake of the `unexpand-abbrev' command. - Variable: last-abbrev-location This is the location of the last abbrev expanded. This contains information left by `expand-abbrev' for the sake of the `unexpand-abbrev' command. - Variable: last-abbrev-text This is the exact expansion text of the last abbrev expanded, as results from case conversion. Its value is `nil' if the abbrev has already been unexpanded. This contains information left by `expand-abbrev' for the sake of the `unexpand-abbrev' command. - Variable: pre-abbrev-expand-hook This is a normal hook whose functions are executed, in sequence, just before any expansion of an abbrev. *Note Hooks::. Since it is a normal hook, the hook functions receive no arguments. However, they can find the abbrev to be expanded by looking in the buffer before point. The following sample code shows a simple use of `pre-abbrev-expand-hook'. If the user terminates an abbrev with a punctuation character, the function issues a prompt. Thus, this hook allows the user to decide whether the abbrev should be expanded, and to abort expansion if it is not desired. (add-hook 'pre-abbrev-expand-hook 'query-if-not-space) ;; This is the function invoked by `pre-abbrev-expand-hook'. ;; If the user terminated the abbrev with a space, the function does ;; nothing (that is, it returns so that the abbrev can expand). If the ;; user entered some other character, this function asks whether ;; expansion should continue. ;; If the user enters the prompt with `y', the function returns ;; `nil' (because of the `not' function), but that is ;; acceptable; the return value has no effect on expansion. (defun query-if-not-space () (if (/= ?\ (preceding-char)) (if (not (y-or-n-p "Do you want to expand this abbrev? ")) (error "Not expanding this abbrev")))) File: elisp, Node: Standard Abbrev Tables, Prev: Abbrev Expansion, Up: Abbrevs Standard Abbrev Tables ====================== Here we list the variables that hold the abbrev tables for the preloaded major modes of Emacs. - Variable: global-abbrev-table This is the abbrev table for mode-independent abbrevs. The abbrevs defined in it apply to all buffers. Each buffer may also have a local abbrev table, whose abbrev definitions take precedence over those in the global table. - Variable: local-abbrev-table The value of this buffer-local variable is the (mode-specific) abbreviation table of the current buffer. - Variable: fundamental-mode-abbrev-table This is the local abbrev table used in Fundamental mode. It is the local abbrev table in all buffers in Fundamental mode. - Variable: text-mode-abbrev-table This is the local abbrev table used in Text mode. - Variable: c-mode-abbrev-table This is the local abbrev table used in C mode. - Variable: lisp-mode-abbrev-table This is the local abbrev table used in Lisp mode and Emacs Lisp mode. File: elisp, Node: Processes, Next: System Interface, Prev: Abbrevs, Up: Top Processes ********* In the terminology of operating systems, a "process" is a space in which a program can execute. Emacs runs in a process. Emacs Lisp programs can invoke other programs in processes of their own. These are called "subprocesses" or "child processes" of the Emacs process, which is their "parent process". A subprocess of Emacs may be "synchronous" or "asynchronous", depending on how it is created. When you create a synchronous subprocess, the Lisp program waits for the subprocess to terminate before continuing execution. When you create an asynchronous subprocess, it can run in parallel with the Lisp program. This kind of subprocess is represented within Emacs by a Lisp object which is also called a "process". Lisp programs can use this object to communicate with the subprocess or to control it. For example, you can send signals, obtain status information, receive output from the process, or send input to it. - Function: processp OBJECT This function returns `t' if OBJECT is a process, `nil' otherwise. * Menu: * Subprocess Creation:: Functions that start subprocesses. * Synchronous Processes:: Details of using synchronous subprocesses. * Asynchronous Processes:: Starting up an asynchronous subprocess. * Deleting Processes:: Eliminating an asynchronous subprocess. * Process Information:: Accessing run-status and other attributes. * Input to Processes:: Sending input to an asynchronous subprocess. * Signals to Processes:: Stopping, continuing or interrupting an asynchronous subprocess. * Output from Processes:: Collecting output from an asynchronous subprocess. * Sentinels:: Sentinels run when process run-status changes. * Transaction Queues:: Transaction-based communication with subprocesses. * TCP:: Opening network connections. File: elisp, Node: Subprocess Creation, Next: Synchronous Processes, Up: Processes Functions that Create Subprocesses ================================== There are three functions that create a new subprocess in which to run a program. One of them, `start-process', creates an asynchronous process and returns a process object (*note Asynchronous Processes::.). The other two, `call-process' and `call-process-region', create a synchronous process and do not return a process object (*note Synchronous Processes::.). Synchronous and asynchronous processes are explained in following sections. Since the three functions are all called in a similar fashion, their common arguments are described here. In all cases, the function's PROGRAM argument specifies the program to be run. An error is signaled if the file is not found or cannot be executed. The actual file containing the program is found by following normal system rules: if the file name is absolute, then the program must be found in the specified file; if the name is relative, then the directories in `exec-path' are searched sequentially for a suitable file. The variable `exec-path' is initialized when Emacs is started, based on the value of the environment variable `PATH'. The standard file name constructs, `~', `.', and `..', are interpreted as usual in `exec-path', but environment variable substitutions (`$HOME', etc.) are not recognized; use `substitute-in-file-name' to perform them (*note File Name Expansion::.). Each of the subprocess-creating functions has a BUFFER-OR-NAME argument which specifies where the standard output from the program will go. If BUFFER-OR-NAME is `nil', that says to discard the output unless a filter function handles it. (*Note Filter Functions::, and *Note Streams::.) Normally, you should avoid having multiple processes send output to the same buffer because their output would be intermixed randomly. All three of the subprocess-creating functions have a `&rest' argument, ARGS. The ARGS must all be strings, and they are supplied to PROGRAM as separate command line arguments. Wildcard characters and other shell constructs are not allowed in these strings, since they are passed directly to the specified program. *Please note:* the argument PROGRAM contains only the name of the program; it may not contain any command-line arguments. Such arguments must be provided via ARGS. The subprocess gets its current directory from the value of `default-directory' (*note File Name Expansion::.). The subprocess inherits its environment from Emacs; but you can specify overrides for it with `process-environment'. *Note System Environment::. - Variable: exec-directory The value of this variable is the name of a directory (a string) that contains programs that come with GNU Emacs, that are intended for Emacs to invoke. The program `wakeup' is an example of such a program; the `display-time' command uses it to get a reminder once per minute. The default value is the name of a directory whose name ends in `arch-lib'. We call the directory `emacs/arch-lib', since its name usually ends that way. We sometimes refer to "the directory `emacs/arch-lib'," when strictly speaking we ought to say, "the directory named by the variable `exec-directory'." Most of the time, there is no difference. (In earlier Emacs versions, prior to version 19, these files lived in the directory `emacs/etc' instead of in `emacs/arch-lib'.) - User Option: exec-path The value of this variable is a list of directories to search for programs to run in subprocesses. Each element is either the name of a directory (i.e., a string), or `nil', which stands for the default directory (which is the value of `default-directory'). The value of `exec-path' is used by `call-process' and `start-process' when the PROGRAM argument is not an absolute file name. File: elisp, Node: Synchronous Processes, Next: Asynchronous Processes, Prev: Subprocess Creation, Up: Processes Creating a Synchronous Process ============================== After a "synchronous process" is created, Emacs waits for the process to terminate before continuing. Starting Dired is an example of this: it runs `ls' in a synchronous process, then modifies the output slightly. Because the process is synchronous, the entire directory listing arrives in the buffer before Emacs tries to do anything with it. While Emacs waits for the synchronous subprocess to terminate, the user can quit by typing `C-g', and the process is killed by sending it a `SIGKILL' signal. *Note Quitting::. The synchronous subprocess functions return `nil' in version 18. In version 19, they will return an indication of how the process terminated. - Function: call-process PROGRAM &optional INFILE BUFFER-OR-NAME DISPLAY &rest ARGS This function calls PROGRAM in a separate process and waits for it to finish. The standard input for the process comes from file INFILE if INFILE is not `nil' and from `/dev/null' otherwise. The process output gets inserted in buffer BUFFER-OR-NAME before point, if that argument names a buffer. If BUFFER-OR-NAME is `t', output is sent to the current buffer; if BUFFER-OR-NAME is `nil', output is discarded. If BUFFER-OR-NAME is the integer 0, `call-process' returns `nil' immediately and discards any output. In this case, the process is not truly synchronous, since it can run in parallel with Emacs; but you can think of it as synchronous in that Emacs is essentially finished with the subprocess as soon as this function returns. If DISPLAY is non-`nil', then `call-process' redisplays the buffer as output is inserted. Otherwise the function does no redisplay, and the results become visible on the screen only when Emacs redisplays that buffer in the normal course of events. The remaining arguments, ARGS, are strings that are supplied as the command line arguments for the program. The value returned by `call-process' (unless you told it not to wait) indicates the reason for process termination. A number gives the exit status of the subprocess; 0 means success, and any other value means failure. If the process terminated with a signal, `call-process' returns a string describing the signal. The examples below are both run with the buffer `foo' current. (call-process "pwd" nil t) => nil ---------- Buffer: foo ---------- /usr/user/lewis/manual ---------- Buffer: foo ---------- (call-process "grep" nil "bar" nil "lewis" "/etc/passwd") => nil ---------- Buffer: bar ---------- lewis:5LTsHm66CSWKg:398:21:Bil Lewis:/user/lewis:/bin/csh ---------- Buffer: bar ---------- The `dired-readin' function contains a good example of the use of `call-process': (call-process "ls" nil buffer nil dired-listing-switches dirname) - Function: call-process-region START END PROGRAM &optional DELETE BUFFER-OR-NAME DISPLAY &rest ARGS This function sends the text between START to END as standard input to a process running PROGRAM. It deletes the text sent if DELETE is non-`nil', which may be useful when the output is going to be inserted back in the current buffer. If BUFFER-OR-NAME names a buffer, the output is inserted in that buffer at point. If BUFFER-OR-NAME is `t', the output is sent to the current buffer. If BUFFER-OR-NAME is `nil', the output is discarded. If BUFFER-OR-NAME is the integer 0, the output is discarded and `call-process' returns `nil' immediately, just as `call-process' would. If DISPLAY is non-`nil', then `call-process-region' redisplays the buffer as output is inserted. Otherwise the function does no redisplay, and the results become visible on the screen only when Emacs redisplays that buffer in the normal course of events. The remaining arguments, ARGS, are strings that are supplied as the command line arguments for the program. The return value of `call-process-region' is just like that of `call-process': `nil' if you told it to return without waiting; otherwise, a number or string which indicates how the subprocess terminated. In the following example, we use `call-process-region' to run the `cat' utility, with standard input being the first five characters in buffer `foo' (the word `input'). `cat' copies its standard input into its standard output. Since the argument BUFFER-OR-NAME is `t', this output is inserted in the current buffer. ---------- Buffer: foo ---------- input-!- ---------- Buffer: foo ---------- (call-process-region 1 6 "cat" nil t) => nil ---------- Buffer: foo ---------- inputinput-!- ---------- Buffer: foo ---------- The `shell-command-on-region' command uses `call-process-region' like this: (call-process-region start end shell-file-name ; Name of program. nil ; Do not delete region. buffer ; Send output to `buffer'. nil ; No redisplay during output. "-c" command) ; Arguments for the shell. File: elisp, Node: Asynchronous Processes, Next: Deleting Processes, Prev: Synchronous Processes, Up: Processes Creating an Asynchronous Process ================================ After an "asynchronous process" is created, Emacs and the Lisp program can continue running immediately. The process may thereafter run in parallel with Emacs, and the two may communicate with each other using the functions described in following sections. Here we describe how to create an asynchronous process, with `start-process'. - Function: start-process NAME BUFFER-OR-NAME PROGRAM &rest ARGS This function creates a new asynchronous subprocess and starts the program PROGRAM running in it. It returns a process object that stands for the new subprocess for Emacs Lisp programs. The argument NAME specifies the name for the process object; if a process with this name already exists, then NAME is modified (by adding `<1>', etc.) to be unique. The buffer BUFFER-OR-NAME is the buffer to associate with the process. The remaining arguments, ARGS, are strings that are supplied as the command line arguments for the program. In the example below, the first process is started and runs (rather, sleeps) for 100 seconds. Meanwhile, the second process is started, given the name `my-process<1>' for the sake of uniqueness. It inserts the directory listing at the end of the buffer `foo', before the first process finishes. Then it finishes, and a message to that effect is inserted in the buffer. Much later, the first process finishes, and another message is inserted in the buffer for it. (start-process "my-process" "foo" "sleep" "100") => #<process my-process> (start-process "my-process" "foo" "ls" "-l" "/user/lewis/bin") => #<process my-process<1>> ---------- Buffer: foo ---------- total 2 lrwxrwxrwx 1 lewis 14 Jul 22 10:12 gnuemacs --> /emacs -rwxrwxrwx 1 lewis 19 Jul 30 21:02 lemon Process my-process<1> finished Process my-process finished ---------- Buffer: foo ---------- - Function: start-process-shell-command NAME BUFFER-OR-NAME COMMAND &rest COMMAND-ARGS This function is like `start-process' except that it uses a shell to execute the specified command. The argument COMMAND is a shell command name, and COMMAND-ARGS are the arguments for the shell command. - Variable: process-connection-type This variable controls the type of device used to communicate with asynchronous subprocesses. If it is `nil', then pipes are used. If it is `t', then PTYs are used (or pipes if PTYs are not supported). PTYs are usually preferable for processes visible to the user, as in Shell mode, because they allow job control (`C-c', `C-z', etc.) to work between the process and its children whereas pipes do not. For subprocesses used for internal purposes by programs, it is often better to use a pipe, because they are more efficient. In addition, the total number of PTYs is limited on many systems and it is good not to waste them. The value `process-connection-type' is used when `start-process' is called, so in order to change it for just one call of `start-process', temporarily rebind it with `let'. (let ((process-connection-type nil)) ; Use a pipe. (start-process ...)) 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. (Use the result of `process-status' to determine which of those it is.) 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. `open' for a network connection that is open. `closed' for a network connection that is closed. Once a connection is closed, you cannot reopen it, though you might be able to open a new connection to the same place. `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 connection, `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'. In earlier Emacs versions (prior to version 19), the status of a network connection was `run' if open, and `exit' if closed. 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 functions 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 signal `SIGINT'. Outside of Emacs, typing the "interrupt character" (normally `C-c' on some systems, and `DEL' on others) 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 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 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 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 signal `SIGCONT'. This presumes that PROCESS-NAME was stopped previously. - Function: signal-process PID SIGNAL This function sends a signal to process PID, which need not be a child of Emacs. The argument SIGNAL specifies which signal to send; it should be an integer. 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, 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. 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* output from that process, that would otherwise have been in a buffer, is passed to the filter. 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 SECONDS MILLISEC 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. 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. Not all operating systems support waiting periods other than multiples of a second; on those that do not, you get an error if you specify nonzero MILLISEC. The function `accept-process-output' returns non-`nil' if it did get some output, or `nil' if the timeout expired before output arrived.