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This is Info file ../../info/lispref.info, produced by Makeinfo version 1.68 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 XEmacs Lisp Reference Manual (for 19.14 and 20.0) v3.1, March 1996 XEmacs Lisp Reference Manual (for 19.15 and 20.1, 20.2) v3.2, April, May 1997 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc. Copyright (C) 1995, 1996 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: Beeping, Prev: Display Tables, Up: Display Beeping ======= You can make XEmacs ring a bell, play a sound, or blink the screen to attract the user's attention. Be conservative about how often you do this; frequent bells can become irritating. Also be careful not to use beeping alone when signaling an error is appropriate. (*Note Errors::.) - Function: ding &optional DONT-TERMINATE SOUND DEVICE This function beeps, or flashes the screen (see `visible-bell' below). It also terminates any keyboard macro currently executing unless DONT-TERMINATE is non-`nil'. If SOUND is specified, it should be a symbol specifying which sound to make. This sound will be played if `visible-bell' is `nil'. (This only works if sound support was compiled into the executable and you are running on the console of a Sun SparcStation, SGI, or HP9000s700. Otherwise you just get a beep.) The optional third argument specifies what device to make the sound on, and defaults to the selected device. - Function: beep &optional DONT-TERMINATE SOUND DEVICE This is a synonym for `ding'. - User Option: visible-bell This variable determines whether XEmacs should flash the screen to represent a bell. Non-`nil' means yes, `nil' means no. On TTY devices, this is effective only if the Termcap entry for the terminal type has the visible bell flag (`vb') set. - Variable: sound-alist This variable holds an alist associating names with sounds. When `beep' or `ding' is called with one of the name symbols, the associated sound will be generated instead of the standard beep. Each element of `sound-alist' is a list describing a sound. The first element of the list is the name of the sound being defined. Subsequent elements of the list are alternating keyword/value pairs: `sound' A string of raw sound data, or the name of another sound to play. The symbol `t' here means use the default X beep. `volume' An integer from 0-100, defaulting to `bell-volume'. `pitch' If using the default X beep, the pitch (Hz) to generate. `duration' If using the default X beep, the duration (milliseconds). For compatibility, elements of `sound-alist' may also be: * `( sound-name . <sound> )' * `( sound-name <volume> <sound> )' You should probably add things to this list by calling the function `load-sound-file'. Caveats: - You can only play audio data if running on the console screen of a Sun SparcStation, SGI, or HP9000s700. - The pitch, duration, and volume options are available everywhere, but many X servers ignore the `pitch' option. The following beep-types are used by XEmacs itself: `auto-save-error' when an auto-save does not succeed `command-error' when the XEmacs command loop catches an error `undefined-key' when you type a key that is undefined `undefined-click' when you use an undefined mouse-click combination `no-completion' during completing-read `y-or-n-p' when you type something other than 'y' or 'n' `yes-or-no-p' when you type something other than 'yes' or 'no' `default' used when nothing else is appropriate. Other lisp packages may use other beep types, but these are the ones that the C kernel of XEmacs uses. - User Option: bell-volume This variable specifies the default volume for sounds, from 0 to 100. - Command: load-default-sounds This function loads and installs some sound files as beep-types. - Command: load-sound-file FILENAME SOUND-NAME &optional VOLUME This function reads in an audio file and adds it to `sound-alist'. The sound file must be in the Sun/NeXT U-LAW format. SOUND-NAME should be a symbol, specifying the name of the sound. If VOLUME is specified, the sound will be played at that volume; otherwise, the value of BELL-VOLUME will be used. - Function: play-sound SOUND &optional VOLUME DEVICE This function plays sound SOUND, which should be a symbol mentioned in `sound-alist'. If VOLUME is specified, it overrides the value (if any) specified in `sound-alist'. DEVICE specifies the device to play the sound on, and defaults to the selected device. - Command: play-sound-file FILE &optional VOLUME DEVICE This function plays the named sound file at volume VOLUME, which defaults to `bell-volume'. DEVICE specifies the device to play the sound on, and defaults to the selected device. File: lispref.info, Node: Hash Tables, Next: Range Tables, Prev: Display, Up: Top Hash Tables *********** - Function: hashtablep OBJECT This function returns non-`nil' if OBJECT is a hash table. * Menu: * Introduction to Hash Tables:: Hash tables are fast data structures for implementing simple tables (i.e. finite mappings from keys to values). * Working With Hash Tables:: Hash table functions. * Weak Hash Tables:: Hash tables with special garbage-collection behavior. File: lispref.info, Node: Introduction to Hash Tables, Next: Working With Hash Tables, Up: Hash Tables Introduction to Hash Tables =========================== A hash table is a data structure that provides mappings from arbitrary Lisp objects (called "keys") to other arbitrary Lisp objects (called "values"). There are many ways other than hash tables of implementing the same sort of mapping, e.g. association lists (*note Association Lists::.) and property lists (*note Property Lists::.), but hash tables provide much faster lookup. When you create a hash table, you specify a size, which indicates the expected number of elements that the table will hold. You are not bound by this size, however; hash tables automatically resize themselves if the number of elements becomes too large. (Internally, hash tables are hashed using a modification of the "linear probing" hash table method. This method hashes each key to a particular spot in the hash table, and then scans forward sequentially until a blank entry is found. To look up a key, hash to the appropriate spot, then search forward for the key until either a key is found or a blank entry stops the search. The modification actually used is called "double hashing" and involves moving forward by a fixed increment, whose value is computed from the original hash value, rather than always moving forward by one. This eliminates problems with clustering that can arise from the simple linear probing method. For more information, see `Algorithms' (second edition) by Robert Sedgewick, pp. 236-241.) - Function: make-hashtable SIZE &optional TEST-FUN This function makes a hash table of initial size SIZE. Comparison between keys is normally done with `eql'; i.e. two keys must be the same object to be considered equivalent. However, you can explicitly specify the comparison function using TEST-FUN, which must be one of `eq', `eql', or `equal'. Note that currently, `eq' and `eql' are the same. This will change when bignums are implemented. - Function: copy-hashtable OLD-TABLE This function makes a new hash table which contains the same keys and values as the given table. The keys and values will not themselves be copied. - Function: hashtable-fullness TABLE This function returns number of entries in TABLE. File: lispref.info, Node: Working With Hash Tables, Next: Weak Hash Tables, Prev: Introduction to Hash Tables, Up: Hash Tables Working With Hash Tables ======================== - Function: puthash KEY VAL TABLE This function hashes KEY to VAL in TABLE. - Function: gethash KEY TABLE &optional DEFAULT This function finds the hash value for KEY in TABLE. If there is no corresponding value, DEFAULT is returned (defaults to `nil'). - Function: remhash KEY TABLE This function removes the hash value for KEY in TABLE. - Function: clrhash TABLE This function flushes TABLE. Afterwards, the hash table will contain no entries. - Function: maphash FUNCTION TABLE This function maps FUNCTION over entries in TABLE, calling it with two args, each key and value in the table. File: lispref.info, Node: Weak Hash Tables, Prev: Working With Hash Tables, Up: Hash Tables Weak Hash Tables ================ A "weak hash table" is a special variety of hash table whose elements do not count as GC referents. For any key-value pair in such a hash table, if either the key or value (or in some cases, if one particular one of the two) has no references to it outside of weak hash tables (and similar structures such as weak lists), the pair will be removed from the table, and the key and value collected. A non-weak hash table (or any other pointer) would prevent the objects from being collected. Weak hash tables are useful for keeping track of information in a non-obtrusive way, for example to implement caching. If the cache contains objects such as buffers, markers, image instances, etc. that will eventually disappear and get garbage-collected, using a weak hash table ensures that these objects are collected normally rather than remaining around forever, long past their actual period of use. (Otherwise, you'd have to explicitly map over the hash table every so often and remove unnecessary elements.) There are three types of weak hash tables: fully weak hash tables In these hash tables, a pair disappears if either the key or the value is unreferenced outside of the table. key-weak hash tables In these hash tables, a pair disappears if the key is unreferenced outside of the table, regardless of how the value is referenced. value-weak hash tables In these hash tables, a pair disappears if the value is unreferenced outside of the table, regardless of how the key is referenced. Also see *Note Weak Lists::. - Function: make-weak-hashtable SIZE &optional TEST-FUN This function makes a fully weak hash table of initial size SIZE. TEST-FUN is as in `make-hashtable'. - Function: make-key-weak-hashtable SIZE &optional TEST-FUN This function makes a key-weak hash table of initial size SIZE. TEST-FUN is as in `make-hashtable'. - Function: make-value-weak-hashtable SIZE &optional TEST-FUN This function makes a value-weak hash table of initial size SIZE. TEST-FUN is as in `make-hashtable'. File: lispref.info, Node: Range Tables, Next: Databases, Prev: Hash Tables, Up: Top Range Tables ************ A range table is a table that efficiently associated values with ranges of integers. Note that range tables have a read syntax, like this: #s(range-table data ((-3 2) foo (5 20) bar)) This maps integers in the range (-3, 2) to `foo' and integers in the range (5, 20) to `bar'. - Function: range-table-p OBJECT Return non-`nil' if OBJECT is a range table. * Menu: * Introduction to Range Tables:: Range tables efficiently map ranges of integers to values. * Working With Range Tables:: Range table functions. File: lispref.info, Node: Introduction to Range Tables, Next: Working With Range Tables, Up: Range Tables Introduction to Range Tables ============================ - Function: make-range-table Make a new, empty range table. - Function: copy-range-table OLD-TABLE Make a new range table which contains the same values for the same ranges as the given table. The values will not themselves be copied. File: lispref.info, Node: Working With Range Tables, Prev: Introduction to Range Tables, Up: Range Tables Working With Range Tables ========================= - Function: get-range-table POS TABLE &optional DEFAULT This function finds value for position POS in TABLE. If there is no corresponding value, return DEFAULT (defaults to `nil'). - Function: put-range-table START END VAL TABLE This function sets the value for range (START, END) to be VAL in TABLE. - Function: remove-range-table START END TABLE This function removes the value for range (START, END) in TABLE. - Function: clear-range-table TABLE This function flushes TABLE. - Function: map-range-table FUNCTION TABLE This function maps FUNCTION over entries in TABLE, calling it with three args, the beginning and end of the range and the corresponding value. File: lispref.info, Node: Databases, Next: Processes, Prev: Range Tables, Up: Top Databases ********* - Function: databasep OBJECT This function returns non-`nil' if OBJECT is a database. * Menu: * Connecting to a Database:: * Working With a Database:: * Other Database Functions:: File: lispref.info, Node: Connecting to a Database, Next: Working With a Database, Up: Databases Connecting to a Database ======================== - Function: open-database FILE &optional TYPE SUBTYPE ACCESS MODE This function opens database FILE, using database method TYPE and SUBTYPE, with access rights ACCESS and permissions MODE. ACCESS can be any combination of `r' `w' and `+', for read, write, and creation flags. TYPE can have the value `'dbm' or `'berkeley_db' to select the type of database file to use. (Note: XEmacs may not support both of these types.) For a TYPE of `'dbm', there are no subtypes, so SUBTYPE should by `nil'. For a TYPE of `'berkeley_db', the following subtypes are available: `'hash', `'btree', and `'recno'. See the manpages for the Berkeley DB functions to more information about these types. - Function: close-database OBJ This function closes database OBJ. - Function: database-live-p OBJ This function returns `t' iff OBJ is an active database, else `nil'. File: lispref.info, Node: Working With a Database, Next: Other Database Functions, Prev: Connecting to a Database, Up: Databases Working With a Database ======================= - Function: get-database KEY DBASE &optional DEFAULT This function finds the value for KEY in DATABASE. If there is no corresponding value, DEFAULT is returned (`nil' if DEFAULT is omitted). - Function: map-database FUNCTION DBASE This function maps FUNCTION over entries in DATABASE, calling it with two args, each key and value in the database. - Function: put-database KEY VAL DBASE &optional REPLACE This function stores KEY and VAL in DATABASE. If optional fourth arg REPLACE is non-`nil', replace any existing entry in the database. - Function: remove-database KEY DBASE This function removes KEY from DATABASE. File: lispref.info, Node: Other Database Functions, Prev: Working With a Database, Up: Databases Other Database Functions ======================== - Function: database-file-name OBJ This function returns the filename associated with the database OBJ. - Function: database-last-error &optional OBJ This function returns the last error associated with database OBJ. - Function: database-subtype OBJ This function returns the subtype of database OBJ, if any. - Function: database-type OBJ This function returns the type of database OBJ. File: lispref.info, Node: Processes, Next: System Interface, Prev: Databases, Up: Top Processes ********* In the terminology of operating systems, a "process" is a space in which a program can execute. XEmacs runs in a process. XEmacs Lisp programs can invoke other programs in processes of their own. These are called "subprocesses" or "child processes" of the XEmacs process, which is their "parent process". A subprocess of XEmacs 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 XEmacs 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. * MS-DOS Subprocesses:: On MS-DOS, you must indicate text vs binary for data sent to and from a subprocess. * 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. * Process Window Size:: Changing the logical window size of a process. * Transaction Queues:: Transaction-based communication with subprocesses. * Network:: Opening network connections. File: lispref.info, 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. If the file name is relative, the variable `exec-path' contains a list of directories to search. Emacs initializes `exec-path' when it starts up, 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 Read and Print::.) 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. You must use ARGS to provide those. The subprocess gets its current directory from the value of `default-directory' (*note File Name Expansion::.). The subprocess inherits its environment from XEmacs; 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 XEmacs, that are intended for XEmacs 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. - 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: lispref.info, Node: Synchronous Processes, Next: MS-DOS Subprocesses, Prev: Subprocess Creation, Up: Processes Creating a Synchronous Process ============================== After a "synchronous process" is created, XEmacs 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 XEmacs tries to do anything with it. While Emacs waits for the synchronous subprocess to terminate, the user can quit by typing `C-g'. The first `C-g' tries to kill the subprocess with a `SIGINT' signal; but it waits until the subprocess actually terminates before quitting. If during that time the user types another `C-g', that kills the subprocess instantly with `SIGKILL' and quits immediately. *Note Quitting::. The synchronous subprocess functions returned `nil' in version 18. In version 19, they return an indication of how the process terminated. - Function: call-process PROGRAM &optional INFILE DESTINATION 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 argument DESTINATION says where to put the process output. Here are the possibilities: a buffer Insert the output in that buffer, before point. This includes both the standard output stream and the standard error stream of the process. a string Find or create a buffer with that name, then insert the output in that buffer, before point. `t' Insert the output in the current buffer, before point. `nil' Discard the output. 0 Discard the output, and return immediately without waiting for the subprocess to finish. 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. (REAL-DESTINATION ERROR-DESTINATION) Keep the standard output stream separate from the standard error stream; deal with the ordinary output as specified by REAL-DESTINATION, and dispose of the error output according to ERROR-DESTINATION. The value `nil' means discard it, `t' means mix it with the ordinary output, and a string specifies a file name to redirect error output into. You can't directly specify a buffer to put the error output in; that is too difficult to implement. But you can achieve this result by sending the error output to a temporary file and then inserting the file into a buffer. 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 XEmacs redisplays that buffer in the normal course of events. The remaining arguments, ARGS, are strings that specify 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. In the examples below, the buffer `foo' is 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 `insert-directory' function contains a good example of the use of `call-process': (call-process insert-directory-program nil t nil switches (if full-directory-p (concat (file-name-as-directory file) ".") file)) - Function: call-process-region START END PROGRAM &optional DELETE DESTINATION 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'; this is useful when BUFFER is `t', to insert the output in the current buffer. The arguments DESTINATION and DISPLAY control what to do with the output from the subprocess, and whether to update the display as it comes in. For details, see the description of `call-process', above. If DESTINATION is the integer 0, `call-process-region' discards the output and returns `nil' immediately, without waiting for the subprocess to finish. The remaining arguments, ARGS, are strings that specify 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 DESTINATION 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: lispref.info, Node: MS-DOS Subprocesses, Next: Asynchronous Processes, Prev: Synchronous Processes, Up: Processes MS-DOS Subprocesses =================== On MS-DOS, you must indicate whether the data going to and from a synchronous subprocess are text or binary. Text data requires translation between the end-of-line convention used within Emacs (a single newline character) and the convention used outside Emacs (the two-character sequence, CRLF). The variable `binary-process-input' applies to input sent to the subprocess, and `binary-process-output' applies to output received from it. A non-`nil' value means the data is non-text; `nil' means the data is text, and calls for conversion. - Variable: binary-process-input If this variable is `nil', convert newlines to CRLF sequences in the input to a synchronous subprocess. - Variable: binary-process-output If this variable is `nil', convert CRLF sequences to newlines in the output from a synchronous subprocess. *Note Files and MS-DOS::, for related information. File: lispref.info, Node: Asynchronous Processes, Next: Deleting Processes, Prev: MS-DOS Subprocesses, Up: Processes Creating an Asynchronous Process ================================ After an "asynchronous process" is created, Emacs and the Lisp program both 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 in Lisp. 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 specify 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, and 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 non-`nil', then PTYs are used, when available. Otherwise, pipes are used. 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 you can specify how to communicate with one subprocess by binding the variable around the call to `start-process'. (let ((process-connection-type nil)) ; Use a pipe. (start-process ...)) To determine whether a given subprocess actually got a pipe or a PTY, use the function `process-tty-name' (*note Process Information::.). File: lispref.info, Node: Deleting Processes, Next: Process Information, Prev: Asynchronous Processes, Up: Processes Deleting Processes ================== "Deleting a process" disconnects XEmacs 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, killing it with a `SIGHUP' signal. The argument NAME may be a process, the name of a process, a buffer, or the name of a buffer. (delete-process "*shell*") => nil - Function: process-kill-without-query PROCESS &optional REQUIRE-QUERY-P This function declares that XEmacs need not query the user if PROCESS is still running when XEmacs is exited. The process will be deleted silently. If REQUIRE-QUERY-P is non-`nil', then XEmacs *will* query the user (this is the default). The return value is `t' if a query was formerly required, and `nil' otherwise. (process-kill-without-query (get-process "shell")) => t File: lispref.info, 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. In addition, it finally deletes any process whose status was `Exited' or `Signaled'. It 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-id PROCESS This function returns the PID of PROCESS. This is an integer that 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 a process, a buffer, a process name (string) or a buffer name (string). 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 (get-buffer "*shell*")) => run 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 XEmacs 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. - Function: process-kill-without-query-p PROCESS This function returns whether PROCESS will be killed without querying the user, if it is running when XEmacs is exited. The default value is `nil'. - 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-tty-name PROCESS This function returns the terminal name that PROCESS is using for its communication with Emacs--or `nil' if it is using pipes instead of a terminal (see `process-connection-type' in *Note Asynchronous Processes::). File: lispref.info, 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 XEmacs, 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, Emacs sends an EOF periodically amidst the other characters, to force them through. For most programs, these EOFs do no harm. - 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. If it is `nil', the current buffer's process is used. 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. (If it is `nil', the current buffer's process is used.) 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: lispref.info, 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. The set of signals and their names is defined by the operating system. 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; XEmacs has facilities for sending only a few of the signals that are defined. XEmacs can send signals only to its own subprocesses. You can send signals explicitly by calling the functions in this section. XEmacs also sends signals automatically at certain times: killing a buffer sends a `SIGHUP' signal to all its associated processes; killing XEmacs 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 XEmacs subprocess. If it is non-`nil', then the signal is sent to the current process-group of the terminal that XEmacs 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 XEmacs. 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 XEmacs, 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 XEmacs 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 XEmacs. - 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 XEmacs). When CURRENT-GROUP is non-`nil', you can think of this function as "typing `C-z'" on the terminal XEmacs 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 XEmacs. The argument SIGNAL specifies which signal to send; it should be an integer. File: lispref.info, 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. If the process has no buffer and no filter function, its output is discarded. * 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: lispref.info, 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 XEmacs 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', 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. - 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 process marker for PROCESS, which is the marker that says where to insert output from the process. If PROCESS does not have a buffer, `process-mark' returns a marker that points nowhere. Insertion of process output in a buffer uses this marker to decide where to insert, and updates it to point after the inserted text. That is why successive batches of output are inserted consecutively. 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 becomes associated with no 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> Killing the process's buffer deletes the process, which kills the subprocess with a `SIGHUP' signal (*note Signals to Processes::.).