1 @c This is part of the Emacs manual.
2 @c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2000, 2001,
3 @c 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
4 @c See file emacs.texi for copying conditions.
5 @node Building, Maintaining, Programs, Top
6 @chapter Compiling and Testing Programs
7 @cindex building programs
8 @cindex program building
9 @cindex running Lisp functions
11 The previous chapter discusses the Emacs commands that are useful for
12 making changes in programs. This chapter deals with commands that assist
13 in the larger process of compiling and testing programs.
16 * Compilation:: Compiling programs in languages other
17 than Lisp (C, Pascal, etc.).
18 * Compilation Mode:: The mode for visiting compiler errors.
19 * Compilation Shell:: Customizing your shell properly
20 for use in the compilation buffer.
21 * Grep Searching:: Searching with grep.
22 * Flymake:: Finding syntax errors on the fly.
23 * Debuggers:: Running symbolic debuggers for non-Lisp programs.
24 * Executing Lisp:: Various modes for editing Lisp programs,
25 with different facilities for running
27 * Libraries: Lisp Libraries. Creating Lisp programs to run in Emacs.
28 * Eval: Lisp Eval. Executing a single Lisp expression in Emacs.
29 * Interaction: Lisp Interaction. Executing Lisp in an Emacs buffer.
30 * External Lisp:: Communicating through Emacs with a separate Lisp.
34 @section Running Compilations under Emacs
35 @cindex inferior process
37 @cindex compilation errors
40 Emacs can run compilers for noninteractive languages such as C and
41 Fortran as inferior processes, feeding the error log into an Emacs buffer.
42 It can also parse the error messages and show you the source lines where
43 compilation errors occurred.
47 Run a compiler asynchronously under Emacs, with error messages going to
48 the @samp{*compilation*} buffer.
50 Invoke a compiler with the same command as in the last invocation of
52 @item M-x kill-compilation
53 Kill the running compilation subprocess.
57 To run @code{make} or another compilation command, do @kbd{M-x
58 compile}. This command reads a shell command line using the minibuffer,
59 and then executes the command in an inferior shell, putting output in
60 the buffer named @samp{*compilation*}. The current buffer's default
61 directory is used as the working directory for the execution of the
62 command; normally, therefore, the compilation happens in this
65 @vindex compile-command
66 The default for the compilation command is normally @samp{make -k},
67 which is correct most of the time for nontrivial programs.
68 (@xref{Top,, Make, make, GNU Make Manual}.) If you have done @kbd{M-x
69 compile} before, the default each time is the command you used the
70 previous time. @code{compile} stores this command in the variable
71 @code{compile-command}, so setting that variable specifies the default
72 for the next use of @kbd{M-x compile}. If a file specifies a file
73 local value for @code{compile-command}, that provides the default when
74 you type @kbd{M-x compile} in that file's buffer. @xref{File
77 Starting a compilation displays the buffer @samp{*compilation*} in
78 another window but does not select it. The buffer's mode line tells
79 you whether compilation is finished, with the word @samp{run},
80 @samp{signal} or @samp{exit} inside the parentheses. You do not have
81 to keep this buffer visible; compilation continues in any case. While
82 a compilation is going on, the string @samp{Compiling} appears in the
83 mode lines of all windows. When this string disappears, the
84 compilation is finished.
86 If you want to watch the compilation transcript as it appears, switch
87 to the @samp{*compilation*} buffer and move point to the end of the
88 buffer. When point is at the end, new compilation output is inserted
89 above point, which remains at the end. If point is not at the end of
90 the buffer, it remains fixed while more compilation output is added at
91 the end of the buffer.
93 @cindex compilation buffer, keeping point at end
94 @vindex compilation-scroll-output
95 If you set the variable @code{compilation-scroll-output} to a
96 non-@code{nil} value, then the compilation buffer always scrolls to
97 follow output as it comes in.
100 To rerun the last compilation with the same command, type @kbd{M-x
101 recompile}. This automatically reuses the compilation command from
102 the last invocation of @kbd{M-x compile}. It also reuses the
103 @samp{*compilation*} buffer and starts the compilation in its default
104 directory, which is the directory in which the previous compilation
107 When the compiler process terminates, for whatever reason, the mode
108 line of the @samp{*compilation*} buffer changes to say @samp{exit}
109 (followed by the exit code, @samp{[0]} for a normal exit), or
110 @samp{signal} (if a signal terminated the process), instead of
113 @findex kill-compilation
114 Starting a new compilation also kills any compilation
115 running in @samp{*compilation*}, as the buffer can only handle one
116 compilation at any time. However, @kbd{M-x compile} asks for
117 confirmation before actually killing a compilation that is running.
118 You can also kill the compilation process with @kbd{M-x
121 If you want to run two compilations at once, you should start the
122 first one, then rename the @samp{*compilation*} buffer (perhaps using
123 @code{rename-uniquely}; @pxref{Misc Buffer}), and start the other
124 compilation. That will create a new @samp{*compilation*} buffer.
126 Emacs does not expect a compiler process to launch asynchronous
127 subprocesses; if it does, and they keep running after the main
128 compiler process has terminated, Emacs may kill them or their output
129 may not arrive in Emacs. To avoid this problem, make the main process
130 wait for its subprocesses to finish. In a shell script, you can do this
131 using @samp{$!} and @samp{wait}, like this:
134 (sleep 10; echo 2nd)& pid=$! # @r{Record pid of subprocess}
136 wait $pid # @r{Wait for subprocess}
139 If the background process does not output to the compilation buffer,
140 so you only need to prevent it from being killed when the main
141 compilation process terminates, this is sufficient:
144 nohup @var{command}; sleep 1
147 @vindex compilation-environment
148 You can control the environment passed to the compilation command
149 with the variable @code{compilation-environment}. Its value is a list
150 of environment variable settings; each element should be a string of
151 the form @code{"@var{envvarname}=@var{value}"}. These environment
152 variable settings override the usual ones.
154 @node Compilation Mode
155 @section Compilation Mode
157 @cindex Compilation mode
158 @cindex mode, Compilation
159 The @samp{*compilation*} buffer uses a special major mode,
160 Compilation mode, whose main feature is to provide a convenient way to
161 visit the source line corresponding to an error message. These
162 commands are also available in other special buffers that list
163 locations in files, including those made by @kbd{M-x grep} and
170 Visit the locus of the next error message or match.
173 Visit the locus of the previous error message or match.
175 Visit the locus of the error message that point is on.
176 This command is used in the compilation buffer.
178 Visit the locus of the error message that you click on.
180 Find and highlight the locus of the next error message, without
181 selecting the source buffer.
183 Find and highlight the locus of the previous error message, without
184 selecting the source buffer.
186 Move point to the next error for a different file than the current
189 Move point to the previous error for a different file than the current
192 Toggle Next Error Follow minor mode, which makes cursor motion in the
193 compilation buffer produce automatic source display.
196 @findex compile-goto-error
197 You can visit the source for any particular error message by moving
198 point in the @samp{*compilation*} buffer to that error message and
199 typing @key{RET} (@code{compile-goto-error}). Alternatively, you can
200 click @kbd{Mouse-2} on the error message; you need not switch to the
201 @samp{*compilation*} buffer first.
207 @vindex next-error-highlight
208 To parse the compiler error messages sequentially, type @kbd{C-x `}
209 (@code{next-error}). The character following the @kbd{C-x} is the
210 backquote or ``grave accent,'' not the single-quote. This command is
211 available in all buffers, not just in @samp{*compilation*}; it
212 displays the next error message at the top of one window and source
213 location of the error in another window. It also momentarily
214 highlights the relevant source line. You can change the behavior of
215 this highlighting with the variable @code{next-error-highlight}.
217 The first time @w{@kbd{C-x `}} is used after the start of a compilation,
218 it moves to the first error's location. Subsequent uses of @kbd{C-x
219 `} advance down to subsequent errors. If you visit a specific error
220 message with @key{RET} or @kbd{Mouse-2}, subsequent @w{@kbd{C-x `}}
221 commands advance from there. When @w{@kbd{C-x `}} gets to the end of the
222 buffer and finds no more error messages to visit, it fails and signals
223 an Emacs error. @w{@kbd{C-u C-x `}} starts scanning from the beginning of
224 the compilation buffer, and goes to the first error's location.
226 @vindex compilation-skip-threshold
227 By default, @w{@kbd{C-x `}} skips less important messages. The variable
228 @code{compilation-skip-threshold} controls this. If its value is 2,
229 @w{@kbd{C-x `}} skips anything less than error, 1 skips anything less
230 than warning, and 0 doesn't skip any messages. The default is 1.
232 When the window has a left fringe, an arrow in the fringe points to
233 the current message in the compilation buffer. The variable
234 @code{compilation-context-lines} controls the number of lines of
235 leading context to display before the current message. Going to an
236 error message location scrolls the @samp{*compilation*} buffer to put
237 the message that far down from the top. The value @code{nil} is
238 special: if there's a left fringe, the window doesn't scroll at all
239 if the message is already visible. If there is no left fringe,
240 @code{nil} means display the message at the top of the window.
242 If you're not in the compilation buffer when you run
243 @code{next-error}, Emacs will look for a buffer that contains error
244 messages. First, it looks for one displayed in the selected frame,
245 then for one that previously had @code{next-error} called on it, and
246 then at the current buffer. Finally, Emacs looks at all the remaining
247 buffers. @code{next-error} signals an error if it can't find any such
250 @vindex compilation-error-regexp-alist
251 @vindex grep-regexp-alist
252 To parse messages from the compiler, Compilation mode uses the
253 variable @code{compilation-error-regexp-alist} which lists various
254 formats of error messages and tells Emacs how to extract the source file
255 and the line number from the text of a message. If your compiler isn't
256 supported, you can tailor Compilation mode to it by adding elements to
257 that list. A similar variable @code{grep-regexp-alist} tells Emacs how
258 to parse output of a @code{grep} command.
260 @findex compilation-next-error
261 @findex compilation-previous-error
262 @findex compilation-next-file
263 @findex compilation-previous-file
264 Compilation mode also redefines the keys @key{SPC} and @key{DEL} to
265 scroll by screenfuls, and @kbd{M-n} (@code{compilation-next-error})
266 and @kbd{M-p} (@code{compilation-previous-error}) to move to the next
267 or previous error message. You can also use @kbd{M-@{}
268 (@code{compilation-next-file} and @kbd{M-@}}
269 (@code{compilation-previous-file}) to move up or down to an error
270 message for a different source file.
272 @cindex Next Error Follow mode
273 @findex next-error-follow-minor-mode
274 You can type @kbd{C-c C-f} to toggle Next Error Follow mode. In
275 this minor mode, ordinary cursor motion in the compilation buffer
276 automatically updates the source buffer. For instance, moving the
277 cursor to the next error message causes the location of that error to
278 be displayed immediately.
280 The features of Compilation mode are also available in a minor mode
281 called Compilation Minor mode. This lets you parse error messages in
282 any buffer, not just a normal compilation output buffer. Type @kbd{M-x
283 compilation-minor-mode} to enable the minor mode. This defines the keys
284 @key{RET} and @kbd{Mouse-2}, as in the Compilation major mode.
286 Compilation minor mode works in any buffer, as long as the contents
287 are in a format that it understands. In an Rlogin buffer (@pxref{Remote
288 Host}), Compilation minor mode automatically accesses remote source
289 files by FTP (@pxref{File Names}).
291 @node Compilation Shell
292 @section Subshells for Compilation
294 Emacs uses a shell to run the compilation command, but specifies the
295 option for a noninteractive shell. This means, in particular, that
296 the shell should start with no prompt. If you find your usual shell
297 prompt making an unsightly appearance in the @samp{*compilation*}
298 buffer, it means you have made a mistake in your shell's init file by
299 setting the prompt unconditionally. (This init file's name may be
300 @file{.bashrc}, @file{.profile}, @file{.cshrc}, @file{.shrc}, or
301 various other things, depending on the shell you use.) The shell init
302 file should set the prompt only if there already is a prompt. Here's
303 how to do it in bash:
306 if [ "$@{PS1+set@}" = set ]
312 And here's how to do it in csh:
315 if ($?prompt) set prompt = @dots{}
318 There may well be other things that your shell's init file
319 ought to do only for an interactive shell. You can use the same
320 method to conditionalize them.
322 The MS-DOS ``operating system'' does not support asynchronous
323 subprocesses; to work around this lack, @kbd{M-x compile} runs the
324 compilation command synchronously on MS-DOS. As a consequence, you must
325 wait until the command finishes before you can do anything else in
326 Emacs. @xref{MS-DOS,,,emacs-xtra,Specialized Emacs Features}.
329 @section Searching with Grep under Emacs
331 Just as you can run a compiler from Emacs and then visit the lines
332 with compilation errors, you can also run @code{grep} and
333 then visit the lines on which matches were found. This works by
334 treating the matches reported by @code{grep} as if they were ``errors.''
338 Run @code{grep} asynchronously under Emacs, with matching lines
339 listed in the buffer named @samp{*grep*}.
342 Run @code{grep} via @code{find}, with user-specified arguments, and
343 collect output in the buffer named @samp{*grep*}.
345 Kill the running @code{grep} subprocess.
349 To run @code{grep}, type @kbd{M-x grep}, then enter a command line
350 that specifies how to run @code{grep}. Use the same arguments you
351 would give @code{grep} when running it normally: a @code{grep}-style
352 regexp (usually in single-quotes to quote the shell's special
353 characters) followed by file names, which may use wildcards. If you
354 specify a prefix argument for @kbd{M-x grep}, it detects the tag
355 (@pxref{Tags}) around point, and puts that into the default
358 The output from @code{grep} goes in the @samp{*grep*} buffer. You
359 can find the corresponding lines in the original files using @w{@kbd{C-x
360 `}}, @key{RET}, and so forth, just like compilation errors.
362 Some grep programs accept a @samp{--color} option to output special
363 markers around matches for the purpose of highlighting. You can make
364 use of this feature by setting @code{grep-highlight-matches} to
365 @code{t}. When displaying a match in the source buffer, the exact
366 match will be highlighted, instead of the entire source line.
370 The command @kbd{M-x grep-find} (also available as @kbd{M-x
371 find-grep}) is similar to @kbd{M-x grep}, but it supplies a different
372 initial default for the command---one that runs both @code{find} and
373 @code{grep}, so as to search every file in a directory tree. See also
374 the @code{find-grep-dired} command, in @ref{Dired and Find}.
377 @section Finding Syntax Errors On The Fly
378 @cindex checking syntax
380 Flymake mode is a minor mode that performs on-the-fly syntax
381 checking for many programming and markup languages, including C, C++,
382 Perl, HTML, and @TeX{}/La@TeX{}. It is somewhat analogous to Flyspell
383 mode, which performs spell checking for ordinary human languages in a
384 similar fashion (@pxref{Spelling}). As you edit a file, Flymake mode
385 runs an appropriate syntax checking tool in the background, using a
386 temporary copy of the buffer. It then parses the error and warning
387 messages, and highlights the erroneous lines in the buffer. The
388 syntax checking tool used depends on the language; for example, for
389 C/C++ files this is usually the C compiler. Flymake can also use
390 build tools such as @code{make} for checking complicated projects.
392 To activate Flymake mode, type @kbd{M-x flymake-mode}. You can move
393 to the errors spotted by Flymake mode with @kbd{M-x
394 flymake-goto-next-error} and @kbd{M-x flymake-goto-prev-error}. To
395 display any error messages associated with the current line, use
396 @kbd{M-x flymake-display-err-menu-for-current-line}.
398 For more details about using Flymake, see @ref{Top, Flymake,
399 Flymake, flymake, The Flymake Manual}.
402 @section Running Debuggers Under Emacs
414 @c Do you believe in GUD?
415 The GUD (Grand Unified Debugger) library provides an interface to
416 various symbolic debuggers from within Emacs. We recommend the
417 debugger GDB, which is free software, but GUD can also run DBX, SDB or
418 XDB. GUD can also serve as an interface to Perl's debugging mode, the
419 Python debugger PDB, the Bash debugger, and to JDB, the Java Debugger.
420 @xref{Debugging,, The Lisp Debugger, elisp, the Emacs Lisp Reference
421 Manual}, for information on debugging Emacs Lisp programs.
424 * Starting GUD:: How to start a debugger subprocess.
425 * Debugger Operation:: Connection between the debugger and source buffers.
426 * Commands of GUD:: Key bindings for common commands.
427 * GUD Customization:: Defining your own commands for GUD.
428 * GDB Graphical Interface:: An enhanced mode that uses GDB features to
429 implement a graphical debugging environment through
434 @subsection Starting GUD
436 There are several commands for starting a debugger, each corresponding
437 to a particular debugger program.
440 @item M-x gdb @key{RET} @var{file} @key{RET}
442 Run GDB as a subprocess of Emacs. By default, this uses an IDE-like
443 graphical interface; see @ref{GDB Graphical Interface}. Only GDB
444 works with the graphical interface.
446 @item M-x dbx @key{RET} @var{file} @key{RET}
448 Run DBX as a subprocess of Emacs. Since Emacs does not implement a
449 graphical interface for DBX, communication with DBX works by typing
450 commands in the GUD interaction buffer. The same is true for all
451 the other supported debuggers.
453 @item M-x xdb @key{RET} @var{file} @key{RET}
455 @vindex gud-xdb-directories
456 Similar, but run XDB. Use the variable
457 @code{gud-xdb-directories} to specify directories to search for source
460 @item M-x sdb @key{RET} @var{file} @key{RET}
462 Similar, but run SDB.
464 Some versions of SDB do not mention source file names in their
465 messages. When you use them, you need to have a valid tags table
466 (@pxref{Tags}) in order for GUD to find functions in the source code.
467 If you have not visited a tags table or the tags table doesn't list one
468 of the functions, you get a message saying @samp{The sdb support
469 requires a valid tags table to work}. If this happens, generate a valid
470 tags table in the working directory and try again.
472 @item M-x bashdb @key{RET} @var{file} @key{RET}
474 Run the bash debugger to debug @var{file}, a shell script.
476 @item M-x perldb @key{RET} @var{file} @key{RET}
478 Run the Perl interpreter in debug mode to debug @var{file}, a Perl program.
480 @item M-x jdb @key{RET} @var{file} @key{RET}
482 Run the Java debugger to debug @var{file}.
484 @item M-x pdb @key{RET} @var{file} @key{RET}
486 Run the Python debugger to debug @var{file}.
489 Each of these commands takes one argument: a command line to invoke
490 the debugger. In the simplest case, specify just the name of the
491 executable file you want to debug. You may also use options that the
492 debugger supports. However, shell wildcards and variables are not
493 allowed. GUD assumes that the first argument not starting with a
494 @samp{-} is the executable file name.
496 @node Debugger Operation
497 @subsection Debugger Operation
499 @cindex fringes, and current execution line in GUD
500 When you run a debugger with GUD using the textual interface, the
501 debugger uses an Emacs buffer for its ordinary input and output. This
502 is called the GUD buffer. Input and output from the program you are
503 debugging also use this buffer.
505 The debugger displays the source files of the program by visiting
506 them in Emacs buffers. An arrow in the left fringe indicates the
507 current execution line.@footnote{On a text-only terminal, the arrow
508 appears as @samp{=>} and overlays the first two text columns.} Moving
509 point in this buffer does not move the arrow. The arrow is not part
510 of the file's text; it appears only on the screen.
512 You can start editing these source files at any time in the buffers
513 that display them. If you do modify a source file, keep in mind that
514 inserting or deleting lines will throw off the arrow's positioning;
515 GUD has no way of figuring out which line corresponded before your
516 changes to the line number in a debugger message. Also, you'll
517 typically have to recompile and restart the program for your changes
518 to be reflected in the debugger's tables.
520 @cindex tooltips with GUD
521 @vindex tooltip-gud-modes
522 @vindex gud-tooltip-mode
523 @vindex gud-tooltip-echo-area
524 The Tooltip facility (@pxref{Tooltips}) provides support for GUD@.
525 You activate this feature by turning on the minor mode
526 @code{gud-tooltip-mode}. Then you can display a variable's value in a
527 tooltip simply by pointing at it with the mouse. In graphical mode,
528 with a C program, you can also display the @code{#define} directive
529 associated with an identifier when the program is not executing. This
530 operates in the GUD buffer and in source buffers with major modes in
531 the list @code{gud-tooltip-modes}. If the variable
532 @code{gud-tooltip-echo-area} is non-@code{nil} then the variable's
533 value is displayed in the echo area.
535 GUD tooltips are disabled when you use GDB in text command mode
536 (@pxref{GDB Graphical Interface}), because displaying an expression's
537 value in GDB can sometimes expand a macro and result in a side effect
538 that interferes with the program's operation. The GDB graphical
539 interface supports GUD tooltips and assures they will not cause side
542 @node Commands of GUD
543 @subsection Commands of GUD
545 The GUD interaction buffer uses a variant of Shell mode, so the
546 Emacs commands of Shell mode are available (@pxref{Shell Mode}). All
547 the usual commands for your debugger are available, and you can use
548 the Shell mode history commands to repeat them. If you wish, you can
549 control your debugger process entirely through this buffer.
551 GUD mode also provides commands for setting and clearing
552 breakpoints, for selecting stack frames, and for stepping through the
553 program. These commands are available both in the GUD buffer and
554 globally, but with different key bindings. It also has its own tool
555 bar from which you can invoke the more common commands by clicking on
556 the appropriate icon. This is particularly useful for repetitive
557 commands like @code{gud-next} and @code{gud-step}, and allows you to
558 keep the GUD buffer hidden.
560 The breakpoint commands are normally used in source file buffers,
561 because that is the easiest way to specify where to set or clear the
562 breakpoint. Here's the global command to set a breakpoint:
567 Set a breakpoint on the source line that point is on.
570 @kindex C-x C-a @r{(GUD)}
571 Here are the other special commands provided by GUD@. The keys
572 starting with @kbd{C-c} are available only in the GUD interaction
573 buffer. The key bindings that start with @kbd{C-x C-a} are available in
574 the GUD interaction buffer and also in source files.
578 @kindex C-c C-l @r{(GUD)}
581 Display in another window the last line referred to in the GUD
582 buffer (that is, the line indicated in the last location message).
583 This runs the command @code{gud-refresh}.
586 @kindex C-c C-s @r{(GUD)}
589 Execute a single line of code (@code{gud-step}). If the line contains
590 a function call, execution stops after entering the called function.
593 @kindex C-c C-n @r{(GUD)}
596 Execute a single line of code, stepping across entire function calls
597 at full speed (@code{gud-next}).
600 @kindex C-c C-i @r{(GUD)}
603 Execute a single machine instruction (@code{gud-stepi}).
607 @kindex C-c C-r @r{(GUD)}
610 Continue execution without specifying any stopping point. The program
611 will run until it hits a breakpoint, terminates, or gets a signal that
612 the debugger is checking for (@code{gud-cont}).
616 @kindex C-c C-d @r{(GUD)}
619 Delete the breakpoint(s) on the current source line, if any
620 (@code{gud-remove}). If you use this command in the GUD interaction
621 buffer, it applies to the line where the program last stopped.
624 @kindex C-c C-t @r{(GUD)}
627 Set a temporary breakpoint on the current source line, if any
628 (@code{gud-tbreak}). If you use this command in the GUD interaction
629 buffer, it applies to the line where the program last stopped.
632 The above commands are common to all supported debuggers. If you are
633 using GDB or (some versions of) DBX, these additional commands are available:
637 @kindex C-c < @r{(GUD)}
640 Select the next enclosing stack frame (@code{gud-up}). This is
641 equivalent to the GDB command @samp{up}.
644 @kindex C-c > @r{(GUD)}
647 Select the next inner stack frame (@code{gud-down}). This is
648 equivalent to the GDB command @samp{down}.
651 If you are using GDB, these additional key bindings are available:
655 @kindex C-c C-r @r{(GUD)}
658 Start execution of the program (@code{gud-run}).
661 @kindex C-c C-u @r{(GUD)}
664 Continue execution to the current line (@code{gud-until}). The
665 program will run until it hits a breakpoint, terminates, gets a signal
666 that the debugger is checking for, or reaches the line on which the
667 cursor currently sits.
670 @kindex TAB @r{(GUD)}
671 @findex gud-gdb-complete-command
672 With GDB, complete a symbol name (@code{gud-gdb-complete-command}).
673 This key is available only in the GUD interaction buffer.
676 @kindex C-c C-f @r{(GUD)}
679 Run the program until the selected stack frame returns or
680 stops for some other reason (@code{gud-finish}).
683 @kindex C-x C-a C-j @r{(GUD)}
685 Only useful in a source buffer, @code{gud-jump} transfers the
686 program's execution point to the current line. In other words, the
687 next line that the program executes will be the one where you gave the
688 command. If the new execution line is in a different function from
689 the previously one, GDB prompts for confirmation since the results may
690 be bizarre. See the GDB manual entry regarding @code{jump} for
694 These commands interpret a numeric argument as a repeat count, when
697 Because @key{TAB} serves as a completion command, you can't use it to
698 enter a tab as input to the program you are debugging with GDB.
699 Instead, type @kbd{C-q @key{TAB}} to enter a tab.
701 @node GUD Customization
702 @subsection GUD Customization
704 @vindex gdb-mode-hook
705 @vindex dbx-mode-hook
706 @vindex sdb-mode-hook
707 @vindex xdb-mode-hook
708 @vindex perldb-mode-hook
709 @vindex pdb-mode-hook
710 @vindex jdb-mode-hook
711 @vindex bashdb-mode-hook
712 On startup, GUD runs one of the following hooks: @code{gdb-mode-hook},
713 if you are using GDB; @code{dbx-mode-hook}, if you are using DBX;
714 @code{sdb-mode-hook}, if you are using SDB; @code{xdb-mode-hook}, if you
715 are using XDB; @code{perldb-mode-hook}, for Perl debugging mode;
716 @code{pdb-mode-hook}, for PDB; @code{jdb-mode-hook}, for JDB;
717 @code{bashdb-mode-hook}, for the Bash debugger. You can
718 use these hooks to define custom key bindings for the debugger
719 interaction buffer. @xref{Hooks}.
721 Here is a convenient way to define a command that sends a particular
722 command string to the debugger, and set up a key binding for it in the
723 debugger interaction buffer:
727 (gud-def @var{function} @var{cmdstring} @var{binding} @var{docstring})
730 This defines a command named @var{function} which sends
731 @var{cmdstring} to the debugger process, and gives it the documentation
732 string @var{docstring}. You can then use the command @var{function} in any
733 buffer. If @var{binding} is non-@code{nil}, @code{gud-def} also binds
734 the command to @kbd{C-c @var{binding}} in the GUD buffer's mode and to
735 @kbd{C-x C-a @var{binding}} generally.
737 The command string @var{cmdstring} may contain certain
738 @samp{%}-sequences that stand for data to be filled in at the time
739 @var{function} is called:
743 The name of the current source file. If the current buffer is the GUD
744 buffer, then the ``current source file'' is the file that the program
746 @c This said, ``the name of the file the program counter was in at the last breakpoint.''
747 @c But I suspect it is really the last stop file.
750 The number of the current source line. If the current buffer is the GUD
751 buffer, then the ``current source line'' is the line that the program
755 The text of the C lvalue or function-call expression at or adjacent to point.
758 The text of the hexadecimal address at or adjacent to point.
761 The numeric argument of the called function, as a decimal number. If
762 the command is used without a numeric argument, @samp{%p} stands for the
765 If you don't use @samp{%p} in the command string, the command you define
766 ignores any numeric argument.
769 @node GDB Graphical Interface
770 @subsection GDB Graphical Interface
772 By default, the command @code{gdb} starts GDB using a graphical
773 interface, using Emacs windows for display program state information.
774 In effect, this makes Emacs into an IDE (interactive development
775 environment). With it, you do not need to use textual GDB commands;
776 you can control the debugging session with the mouse.
778 @c @findex gdb-mouse-set-clear-breakpoint
779 @c @findex gdb-mouse-toggle-breakpoint
780 For example, you can click @kbd{Mouse-1} in the fringe or display
781 margin of a source buffer to set a breakpoint there and, on a
782 graphical display, a red bullet will appear on that line. If a
783 breakpoint already exists on that line, the same click will remove it.
784 You can also enable or disable a breakpoint by clicking @kbd{Mouse-3}
785 on the bullet. If you drag the debugger arrow in the fringe with
786 @kbd{Mouse-1} (@code{gdb-mouse-until}), execution will continue to the
787 line where you release the button, provided it is still in the same
788 frame. Alternatively, you can click @kbd{Mouse-2} at some point in
789 the fringe of this buffer and execution will advance to there.
791 This mode requires telling GDB that its ``screen size'' is
792 unlimited, so it sets the height and width accordingly. For correct
793 operation you must not change these values during the GDB session.
795 @vindex gud-gdb-command-name
797 You can also run GDB in text command mode, like other debuggers. To
798 do this, set @code{gud-gdb-command-name} to @code{"gdb --fullname"} or
799 edit the startup command in the minibuffer to say that. You need to
800 do use text command mode to run multiple debugging sessions within one
801 Emacs session. If you have customized @code{gud-gdb-command-name} in
802 that way, you can use @kbd{M-x gdba} to invoke GDB in graphical mode.
805 * GDB User Interface Layout:: Control the number of displayed buffers.
806 * Breakpoints Buffer:: A breakpoint control panel.
807 * Stack Buffer:: Select a frame from the call stack.
808 * Watch Expressions:: Monitor variable values in the speedbar.
809 * Other GDB User Interface Buffers:: Input/output, locals, registers,
810 assembler, threads and memory buffers.
813 @node GDB User Interface Layout
814 @subsubsection GDB User Interface Layout
815 @cindex GDB User Interface layout
817 @vindex gdb-many-windows
818 If the variable @code{gdb-many-windows} is @code{nil} (the default
819 value) then @kbd{M-x gdb} normally displays only the GUD buffer.
820 However, if the variable @code{gdb-show-main} is also non-@code{nil},
821 it starts with two windows: one displaying the GUD buffer, and the
822 other showing the source for the @code{main} function of the program
825 If @code{gdb-many-windows} is non-@code{nil}, then @kbd{M-x gdb}
826 displays the following frame layout:
829 +--------------------------------+--------------------------------+
831 | GUD buffer (I/O of GDB) | Locals buffer |
833 |--------------------------------+--------------------------------+
835 | Source buffer | I/O buffer for debugged pgm |
837 |--------------------------------+--------------------------------+
839 | Stack buffer | Breakpoints buffer |
841 +--------------------------------+--------------------------------+
844 However, if @code{gdb-use-separate-io-buffer} is @code{nil}, the I/O
845 buffer does not appear and the source buffer occupies the full width
848 @findex gdb-restore-windows
849 If you change the window layout, for example, while editing and
850 re-compiling your program, then you can restore this standard window
851 layout with the command @code{gdb-restore-windows}.
853 @findex gdb-many-windows
854 To switch between this standard layout and a simple layout
855 containing just the GUD buffer and a source file, type @kbd{M-x
858 You may also specify additional GUD-related buffers to display,
859 either in the same frame or a different one. Select the buffers you
860 want with the @samp{GUD->GDB-windows} and @samp{GUD->GDB-Frames}
861 sub-menus. If the menu-bar is unavailable, type @code{M-x
862 gdb-display-@var{buffertype}-buffer} or @code{M-x
863 gdb-frame-@var{buffertype}-buffer} respectively, where
864 @var{buffertype} is the relevant buffer type, such as
865 @samp{breakpoints}. Most of these buffers are read-only, and typing
866 @kbd{q} in them kills them.
868 When you finish debugging, kill the GUD buffer with @kbd{C-x k},
869 which will also kill all the buffers associated with the session.
870 However you need not do this if, after editing and re-compiling your
871 source code within Emacs, you wish continue debugging. When you
872 restart execution, GDB will automatically find your new executable.
873 Keeping the GUD buffer has the advantage of keeping the shell history
874 as well as GDB's breakpoints. You do need to check that the
875 breakpoints in recently edited source files are still in the right
878 @node Breakpoints Buffer
879 @subsubsection Breakpoints Buffer
881 The breakpoints buffer shows the existing breakpoints and
882 watchpoints (@pxref{Breakpoints,,, gdb, The GNU debugger}). It has
883 these special commands, which mostly apply to the @dfn{current
884 breakpoint}, the breakpoint which point is on.
888 @kindex SPC @r{(GDB breakpoints buffer)}
889 @findex gdb-toggle-breakpoint
890 Enable/disable the current breakpoint (@code{gdb-toggle-breakpoint}).
891 On a graphical display, this changes the color of a bullet in the
892 margin of the source buffer at the relevant line. This is red when
893 the breakpoint is enabled and grey when it is disabled. Text-only
894 terminals correspondingly display a @samp{B} or @samp{b}.
897 @kindex D @r{(GDB breakpoints buffer)}
898 @findex gdb-delete-breakpoint
899 Delete the current breakpoint (@code{gdb-delete-breakpoint}).
902 @kindex RET @r{(GDB breakpoints buffer)}
903 @findex gdb-goto-breakpoint
904 Visit the source line for the current breakpoint
905 (@code{gdb-goto-breakpoint}).
908 @kindex Mouse-2 @r{(GDB breakpoints buffer)}
909 Visit the source line for the breakpoint you click on.
913 @subsubsection Stack Buffer
915 The stack buffer displays a @dfn{call stack}, with one line for each
916 of the nested subroutine calls (@dfn{stack frames}) now active in the
917 program. @xref{Backtrace,, Backtraces, gdb, The GNU debugger}.
919 @findex gdb-frames-select
920 The selected frame number is displayed in reverse contrast. To
921 select a frame in GDB, move point in the stack buffer to that stack
922 frame and type @key{RET} (@code{gdb-frames-select}), or click
923 @kbd{Mouse-2} on a stack frame. If the locals buffer is visible,
924 selecting a stack frame updates it to display the local variables of
927 @node Watch Expressions
928 @subsubsection Watch Expressions
929 @cindex Watching expressions in GDB
932 If you want to see how a variable changes each time your program
933 stops, move point into the variable name and click on the watch icon
934 in the tool bar (@code{gud-watch}).
936 Each watch expression is displayed in the speedbar. Complex data
937 types, such as arrays, structures and unions are represented in a tree
938 format. Leaves and simple data types show the name of the expression
939 and its value and, when the speedbar frame is selected, display the
940 type as a tooltip. Higher levels show the name, type and address
941 value for pointers and just the name and type otherwise.
943 To expand or contract a complex data type, click @kbd{Mouse-2}
944 on the tag to the left of the expression.
946 @findex gdb-var-delete
947 To delete a complex watch expression, move point to the root
948 expression in the speedbar and type @kbd{D} (@code{gdb-var-delete}).
950 @kindex RET @r{(GDB speedbar)}
951 @findex gdb-edit-value
952 To edit a variable with a simple data type, or a simple element of a
953 complex data type, move point there in the speedbar and type @key{RET}
954 (@code{gdb-edit-value}). Or you can click @kbd{Mouse-2} on a value to
955 edit it. Either way, this reads the new value using the minibuffer.
957 @vindex gdb-show-changed-values
958 If you set the variable @code{gdb-show-changed-values} to
959 non-@code{nil} (the default value), Emacs uses
960 @code{font-lock-warning-face} to highlight values that have recently
961 changed and @code{shadow} face to make variables which have gone out of
962 scope less noticeable. When a variable goes out of scope you can't
965 @vindex gdb-use-colon-colon-notation
966 If the variable @code{gdb-use-colon-colon-notation} is
967 non-@code{nil}, Emacs uses the @samp{@var{function}::@var{variable}}
968 format to display variables in the speedbar. Since this does not work
969 for variables defined in compound statements, the default value is
972 @vindex gdb-speedbar-auto-raise
973 To automatically raise the speedbar every time the display of watch
974 expressions updates, set @code{gdb-speedbar-auto-raise} to
975 non-@code{nil}. This can be useful if you are debugging with a full
978 @node Other GDB User Interface Buffers
979 @subsubsection Other Buffers
982 @item Input/Output Buffer
983 @vindex gdb-use-separate-io-buffer
984 If the variable @code{gdb-use-separate-io-buffer} is non-@code{nil},
985 the executable program that is being debugged takes its input and
986 displays its output here. Otherwise it uses the GUD buffer for that.
987 To toggle whether GUD mode uses this buffer, do @kbd{M-x
988 gdb-use-separate-io-buffer}. That takes effect when you next
989 restart the program you are debugging.
991 The history and replay commands from Shell mode are available here,
992 as are the commands to send signals to the program you are debugging.
996 The locals buffer displays the values of local variables of the
997 current frame for simple data types (@pxref{Frame Info, Frame Info,
998 Information on a frame, gdb, The GNU debugger}).
1000 Arrays and structures display their type only. With GDB 6.4 or later,
1001 move point to their name and press @key{RET}, or alternatively click
1002 @kbd{Mouse-2} there, to examine their values. With earlier versions
1003 of GDB, use @kbd{Mouse-2} or @key{RET} on the type description
1004 (@samp{[struct/union]} or @samp{[array]}). @xref{Watch Expressions}.
1006 @item Registers Buffer
1007 @findex toggle-gdb-all-registers
1008 The registers buffer displays the values held by the registers
1009 (@pxref{Registers,,, gdb, The GNU debugger}). Press @key{RET} or
1010 click @kbd{Mouse-2} on a register if you want to change its value.
1011 With GDB 6.4 or later, recently changed register values display with
1012 @code{font-lock-warning-face}. With earlier versions of GDB, you can
1013 press @key{SPC} to toggle the display of floating point registers
1014 (@code{toggle-gdb-all-registers}).
1016 @item Assembler Buffer
1017 The assembler buffer displays the current frame as machine code. An
1018 arrow points to the current instruction, and you can set and remove
1019 breakpoints as in a source buffer. Breakpoint icons also appear in
1020 the fringe or margin.
1022 @item Threads Buffer
1023 @findex gdb-threads-select
1024 The threads buffer displays a summary of all threads currently in your
1025 program (@pxref{Threads, Threads, Debugging programs with multiple
1026 threads, gdb, The GNU debugger}). Move point to any thread in the
1027 list and press @key{RET} to select it (@code{gdb-threads-select}) and
1028 display the associated source in the source buffer. Alternatively,
1029 click @kbd{Mouse-2} on a thread to select it. If the locals buffer is
1030 visible, its contents update to display the variables that are local
1034 The memory buffer lets you examine sections of program memory
1035 (@pxref{Memory, Memory, Examining memory, gdb, The GNU debugger}).
1036 Click @kbd{Mouse-1} on the appropriate part of the header line to
1037 change the starting address or number of data items that the buffer
1038 displays. Click @kbd{Mouse-3} on the header line to select the
1039 display format or unit size for these data items.
1043 @node Executing Lisp
1044 @section Executing Lisp Expressions
1046 Emacs has several different major modes for Lisp and Scheme. They are
1047 the same in terms of editing commands, but differ in the commands for
1048 executing Lisp expressions. Each mode has its own purpose.
1051 @item Emacs-Lisp mode
1052 The mode for editing source files of programs to run in Emacs Lisp.
1053 This mode defines @kbd{C-M-x} to evaluate the current defun.
1054 @xref{Lisp Libraries}.
1055 @item Lisp Interaction mode
1056 The mode for an interactive session with Emacs Lisp. It defines
1057 @kbd{C-j} to evaluate the sexp before point and insert its value in the
1058 buffer. @xref{Lisp Interaction}.
1060 The mode for editing source files of programs that run in Lisps other
1061 than Emacs Lisp. This mode defines @kbd{C-M-x} to send the current defun
1062 to an inferior Lisp process. @xref{External Lisp}.
1063 @item Inferior Lisp mode
1064 The mode for an interactive session with an inferior Lisp process.
1065 This mode combines the special features of Lisp mode and Shell mode
1066 (@pxref{Shell Mode}).
1068 Like Lisp mode but for Scheme programs.
1069 @item Inferior Scheme mode
1070 The mode for an interactive session with an inferior Scheme process.
1073 Most editing commands for working with Lisp programs are in fact
1074 available globally. @xref{Programs}.
1076 @node Lisp Libraries
1077 @section Libraries of Lisp Code for Emacs
1079 @cindex loading Lisp code
1081 Lisp code for Emacs editing commands is stored in files whose names
1082 conventionally end in @file{.el}. This ending tells Emacs to edit them in
1083 Emacs-Lisp mode (@pxref{Executing Lisp}).
1086 Emacs Lisp code can be compiled into byte-code, which loads faster,
1087 takes up less space, and executes faster. @xref{Byte Compilation,,
1088 Byte Compilation, elisp, the Emacs Lisp Reference Manual}. By
1089 convention, the compiled code for a library goes in a separate file
1090 whose name ends in @samp{.elc}. Thus, the compiled code for
1091 @file{foo.el} goes in @file{foo.elc}.
1094 To execute a file of Emacs Lisp code, use @kbd{M-x load-file}. This
1095 command reads a file name using the minibuffer and then executes the
1096 contents of that file as Lisp code. It is not necessary to visit the
1097 file first; in any case, this command reads the file as found on disk,
1098 not text in an Emacs buffer.
1101 @findex load-library
1102 Once a file of Lisp code is installed in the Emacs Lisp library
1103 directories, users can load it using @kbd{M-x load-library}. Programs
1104 can load it by calling @code{load}, a more primitive function that is
1105 similar but accepts some additional arguments.
1107 @kbd{M-x load-library} differs from @kbd{M-x load-file} in that it
1108 searches a sequence of directories and tries three file names in each
1109 directory. Suppose your argument is @var{lib}; the three names are
1110 @file{@var{lib}.elc}, @file{@var{lib}.el}, and lastly just
1111 @file{@var{lib}}. If @file{@var{lib}.elc} exists, it is by convention
1112 the result of compiling @file{@var{lib}.el}; it is better to load the
1113 compiled file, since it will load and run faster.
1115 If @code{load-library} finds that @file{@var{lib}.el} is newer than
1116 @file{@var{lib}.elc} file, it issues a warning, because it's likely
1117 that somebody made changes to the @file{.el} file and forgot to
1118 recompile it. Nonetheless, it loads @file{@var{lib}.elc}. This is
1119 because people often leave unfinished edits the source file, and don't
1120 recompile it until they think it is ready to use.
1122 Because the argument to @code{load-library} is usually not in itself
1123 a valid file name, file name completion is not available. Indeed, when
1124 using this command, you usually do not know exactly what file name
1128 The sequence of directories searched by @kbd{M-x load-library} is
1129 specified by the variable @code{load-path}, a list of strings that are
1130 directory names. The default value of the list contains the directories where
1131 the Lisp code for Emacs itself is stored. If you have libraries of
1132 your own, put them in a single directory and add that directory
1133 to @code{load-path}. @code{nil} in this list stands for the current default
1134 directory, but it is probably not a good idea to put @code{nil} in the
1135 list. If you find yourself wishing that @code{nil} were in the list,
1136 most likely what you really want to do is use @kbd{M-x load-file}
1140 Often you do not have to give any command to load a library, because
1141 the commands defined in the library are set up to @dfn{autoload} that
1142 library. Trying to run any of those commands calls @code{load} to load
1143 the library; this replaces the autoload definitions with the real ones
1146 @vindex load-dangerous-libraries
1147 @cindex Lisp files byte-compiled by XEmacs
1148 By default, Emacs refuses to load compiled Lisp files which were
1149 compiled with XEmacs, a modified versions of Emacs---they can cause
1150 Emacs to crash. Set the variable @code{load-dangerous-libraries} to
1151 @code{t} if you want to try loading them.
1154 @section Evaluating Emacs Lisp Expressions
1155 @cindex Emacs-Lisp mode
1156 @cindex mode, Emacs-Lisp
1158 @findex emacs-lisp-mode
1159 Lisp programs intended to be run in Emacs should be edited in
1160 Emacs-Lisp mode; this happens automatically for file names ending in
1161 @file{.el}. By contrast, Lisp mode itself is used for editing Lisp
1162 programs intended for other Lisp systems. To switch to Emacs-Lisp mode
1163 explicitly, use the command @kbd{M-x emacs-lisp-mode}.
1165 For testing of Lisp programs to run in Emacs, it is often useful to
1166 evaluate part of the program as it is found in the Emacs buffer. For
1167 example, after changing the text of a Lisp function definition,
1168 evaluating the definition installs the change for future calls to the
1169 function. Evaluation of Lisp expressions is also useful in any kind of
1170 editing, for invoking noninteractive functions (functions that are
1175 Read a single Lisp expression in the minibuffer, evaluate it, and print
1176 the value in the echo area (@code{eval-expression}).
1178 Evaluate the Lisp expression before point, and print the value in the
1179 echo area (@code{eval-last-sexp}).
1181 Evaluate the defun containing or after point, and print the value in
1182 the echo area (@code{eval-defun}).
1183 @item M-x eval-region
1184 Evaluate all the Lisp expressions in the region.
1185 @item M-x eval-current-buffer
1186 Evaluate all the Lisp expressions in the buffer.
1190 @c This uses ``colon'' instead of a literal `:' because Info cannot
1191 @c cope with a `:' in a menu
1192 @kindex M-@key{colon}
1197 @findex eval-expression
1198 @kbd{M-:} (@code{eval-expression}) is the most basic command for evaluating
1199 a Lisp expression interactively. It reads the expression using the
1200 minibuffer, so you can execute any expression on a buffer regardless of
1201 what the buffer contains. When the expression is evaluated, the current
1202 buffer is once again the buffer that was current when @kbd{M-:} was
1205 @kindex C-M-x @r{(Emacs-Lisp mode)}
1207 In Emacs-Lisp mode, the key @kbd{C-M-x} is bound to the command
1208 @code{eval-defun}, which parses the defun containing or following point
1209 as a Lisp expression and evaluates it. The value is printed in the echo
1210 area. This command is convenient for installing in the Lisp environment
1211 changes that you have just made in the text of a function definition.
1213 @kbd{C-M-x} treats @code{defvar} expressions specially. Normally,
1214 evaluating a @code{defvar} expression does nothing if the variable it
1215 defines already has a value. But @kbd{C-M-x} unconditionally resets the
1216 variable to the initial value specified in the @code{defvar} expression.
1217 @code{defcustom} expressions are treated similarly.
1218 This special feature is convenient for debugging Lisp programs.
1219 Typing @kbd{C-M-x} on a @code{defface} expression reinitializes
1220 the face according to the @code{defface} specification.
1223 @findex eval-last-sexp
1224 The command @kbd{C-x C-e} (@code{eval-last-sexp}) evaluates the Lisp
1225 expression preceding point in the buffer, and displays the value in the
1226 echo area. It is available in all major modes, not just Emacs-Lisp
1227 mode. It does not treat @code{defvar} specially.
1229 When the result of an evaluation is an integer, you can type
1230 @kbd{C-x C-e} a second time to display the value of the integer result
1231 in additional formats (octal, hexadecimal, and character).
1233 If @kbd{C-x C-e}, or @kbd{M-:} is given a numeric argument, it
1234 inserts the value into the current buffer at point, rather than
1235 displaying it in the echo area. The argument's value does not matter.
1236 @kbd{C-M-x} with a numeric argument instruments the function
1237 definition for Edebug (@pxref{Instrumenting, Instrumenting for Edebug,, elisp, the Emacs Lisp Reference Manual}).
1240 @findex eval-current-buffer
1241 The most general command for evaluating Lisp expressions from a buffer
1242 is @code{eval-region}. @kbd{M-x eval-region} parses the text of the
1243 region as one or more Lisp expressions, evaluating them one by one.
1244 @kbd{M-x eval-current-buffer} is similar but evaluates the entire
1245 buffer. This is a reasonable way to install the contents of a file of
1246 Lisp code that you are ready to test. Later, as you find bugs and
1247 change individual functions, use @kbd{C-M-x} on each function that you
1248 change. This keeps the Lisp world in step with the source file.
1250 @vindex eval-expression-print-level
1251 @vindex eval-expression-print-length
1252 @vindex eval-expression-debug-on-error
1253 The customizable variables @code{eval-expression-print-level} and
1254 @code{eval-expression-print-length} control the maximum depth and length
1255 of lists to print in the result of the evaluation commands before
1256 abbreviating them. @code{eval-expression-debug-on-error} controls
1257 whether evaluation errors invoke the debugger when these commands are
1258 used; its default is @code{t}.
1260 @node Lisp Interaction
1261 @section Lisp Interaction Buffers
1263 The buffer @samp{*scratch*} which is selected when Emacs starts up is
1264 provided for evaluating Lisp expressions interactively inside Emacs.
1266 The simplest way to use the @samp{*scratch*} buffer is to insert Lisp
1267 expressions and type @kbd{C-j} after each expression. This command
1268 reads the Lisp expression before point, evaluates it, and inserts the
1269 value in printed representation before point. The result is a complete
1270 typescript of the expressions you have evaluated and their values.
1272 The @samp{*scratch*} buffer's major mode is Lisp Interaction mode, which
1273 is the same as Emacs-Lisp mode except for the binding of @kbd{C-j}.
1275 @findex lisp-interaction-mode
1276 The rationale for this feature is that Emacs must have a buffer when
1277 it starts up, but that buffer is not useful for editing files since a
1278 new buffer is made for every file that you visit. The Lisp interpreter
1279 typescript is the most useful thing I can think of for the initial
1280 buffer to do. Type @kbd{M-x lisp-interaction-mode} to put the current
1281 buffer in Lisp Interaction mode.
1284 An alternative way of evaluating Emacs Lisp expressions interactively
1285 is to use Inferior Emacs-Lisp mode, which provides an interface rather
1286 like Shell mode (@pxref{Shell Mode}) for evaluating Emacs Lisp
1287 expressions. Type @kbd{M-x ielm} to create an @samp{*ielm*} buffer
1288 which uses this mode. For more information see that command's
1292 @section Running an External Lisp
1294 Emacs has facilities for running programs in other Lisp systems. You can
1295 run a Lisp process as an inferior of Emacs, and pass expressions to it to
1296 be evaluated. You can also pass changed function definitions directly from
1297 the Emacs buffers in which you edit the Lisp programs to the inferior Lisp
1301 @vindex inferior-lisp-program
1303 To run an inferior Lisp process, type @kbd{M-x run-lisp}. This runs
1304 the program named @code{lisp}, the same program you would run by typing
1305 @code{lisp} as a shell command, with both input and output going through
1306 an Emacs buffer named @samp{*lisp*}. That is to say, any ``terminal
1307 output'' from Lisp will go into the buffer, advancing point, and any
1308 ``terminal input'' for Lisp comes from text in the buffer. (You can
1309 change the name of the Lisp executable file by setting the variable
1310 @code{inferior-lisp-program}.)
1312 To give input to Lisp, go to the end of the buffer and type the input,
1313 terminated by @key{RET}. The @samp{*lisp*} buffer is in Inferior Lisp
1314 mode, which combines the special characteristics of Lisp mode with most
1315 of the features of Shell mode (@pxref{Shell Mode}). The definition of
1316 @key{RET} to send a line to a subprocess is one of the features of Shell
1320 For the source files of programs to run in external Lisps, use Lisp
1321 mode. You can switch to this mode with @kbd{M-x lisp-mode}, and it is
1322 used automatically for files whose names end in @file{.l},
1323 @file{.lsp}, or @file{.lisp}.
1325 @kindex C-M-x @r{(Lisp mode)}
1326 @findex lisp-eval-defun
1327 When you edit a function in a Lisp program you are running, the easiest
1328 way to send the changed definition to the inferior Lisp process is the key
1329 @kbd{C-M-x}. In Lisp mode, this runs the function @code{lisp-eval-defun},
1330 which finds the defun around or following point and sends it as input to
1331 the Lisp process. (Emacs can send input to any inferior process regardless
1332 of what buffer is current.)
1334 Contrast the meanings of @kbd{C-M-x} in Lisp mode (for editing
1335 programs to be run in another Lisp system) and Emacs-Lisp mode (for
1336 editing Lisp programs to be run in Emacs; see @pxref{Lisp Eval}): in
1337 both modes it has the effect of installing the function definition
1338 that point is in, but the way of doing so is different according to
1339 where the relevant Lisp environment is found.
1343 arch-tag: 9c3c2f71-b332-4144-8500-3ff9945a50ed