This is ../info/emacs, produced by makeinfo version 4.3 from emacs.texi. This is the Fourteenth edition of the `GNU Emacs Manual', updated for Emacs version 21.3. INFO-DIR-SECTION Emacs START-INFO-DIR-ENTRY * Emacs: (emacs). The extensible self-documenting text editor. END-INFO-DIR-ENTRY Published by the Free Software Foundation 59 Temple Place, Suite 330 Boston, MA 02111-1307 USA Copyright (C) 1985,1986,1987,1993,1994,1995,1996,1997,1998,1999,2000,2001,2002 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being "The GNU Manifesto", "Distribution" and "GNU GENERAL PUBLIC LICENSE", with the Front-Cover texts being "A GNU Manual," and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled "GNU Free Documentation License." (a) The FSF's Back-Cover Text is: "You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development."  File: emacs, Node: Comments in C, Prev: Other C Commands, Up: C Modes Comments in C Modes ------------------- C mode and related modes use a number of variables for controlling comment format. `c-comment-only-line-offset' Extra offset for line which contains only the start of a comment. It can be either an integer or a cons cell of the form `(NON-ANCHORED-OFFSET . ANCHORED-OFFSET)', where NON-ANCHORED-OFFSET is the amount of offset given to non-column-zero anchored comment-only lines, and ANCHORED-OFFSET is the amount of offset to give column-zero anchored comment-only lines. Just an integer as value is equivalent to `(VAL . 0)'. `c-comment-start-regexp' This buffer-local variable specifies how to recognize the start of a comment. `c-hanging-comment-ender-p' If this variable is `nil', `c-fill-paragraph' leaves the comment terminator of a block comment on a line by itself. The default value is `t', which puts the comment-end delimiter `*/' at the end of the last line of the comment text. `c-hanging-comment-starter-p' If this variable is `nil', `c-fill-paragraph' leaves the starting delimiter of a block comment on a line by itself. The default value is `t', which puts the comment-start delimiter `/*' at the beginning of the first line of the comment text.  File: emacs, Node: Fortran, Next: Asm Mode, Prev: C Modes, Up: Programs Fortran Mode ============ Fortran mode provides special motion commands for Fortran statements and subprograms, and indentation commands that understand Fortran conventions of nesting, line numbers and continuation statements. Fortran mode has its own Auto Fill mode that breaks long lines into proper Fortran continuation lines. Special commands for comments are provided because Fortran comments are unlike those of other languages. Built-in abbrevs optionally save typing when you insert Fortran keywords. Use `M-x fortran-mode' to switch to this major mode. This command runs the hook `fortran-mode-hook' (*note Hooks::). Fortran mode is meant for editing Fortran77 "fixed format" source code. For editing the modern Fortran90 "free format" source code, use F90 mode (`f90-mode'). Emacs normally uses Fortran mode for files with extension `.f', `.F' or `.for', and F90 mode for the extension `.f90'. GNU Fortran supports both kinds of format. * Menu: * Motion: Fortran Motion. Moving point by statements or subprograms. * Indent: Fortran Indent. Indentation commands for Fortran. * Comments: Fortran Comments. Inserting and aligning comments. * Autofill: Fortran Autofill. Auto fill minor mode for Fortran. * Columns: Fortran Columns. Measuring columns for valid Fortran. * Abbrev: Fortran Abbrev. Built-in abbrevs for Fortran keywords.  File: emacs, Node: Fortran Motion, Next: Fortran Indent, Up: Fortran Motion Commands --------------- In addition to the normal commands for moving by and operating on "defuns" (Fortran subprograms--functions and subroutines), Fortran mode provides special commands to move by statements. `C-c C-n' Move to beginning of current or next statement (`fortran-next-statement'). `C-c C-p' Move to beginning of current or previous statement (`fortran-previous-statement').  File: emacs, Node: Fortran Indent, Next: Fortran Comments, Prev: Fortran Motion, Up: Fortran Fortran Indentation ------------------- Special commands and features are needed for indenting Fortran code in order to make sure various syntactic entities (line numbers, comment line indicators and continuation line flags) appear in the columns that are required for standard Fortran. * Menu: * Commands: ForIndent Commands. Commands for indenting and filling Fortran. * Contline: ForIndent Cont. How continuation lines indent. * Numbers: ForIndent Num. How line numbers auto-indent. * Conv: ForIndent Conv. Conventions you must obey to avoid trouble. * Vars: ForIndent Vars. Variables controlling Fortran indent style.  File: emacs, Node: ForIndent Commands, Next: ForIndent Cont, Up: Fortran Indent Fortran Indentation and Filling Commands ........................................ `C-M-j' Break the current line and set up a continuation line (`fortran-split-line'). `M-^' Join this line to the previous line (`fortran-join-line'). `C-M-q' Indent all the lines of the subprogram point is in (`fortran-indent-subprogram'). `M-q' Fill a comment block or statement. The key `C-M-q' runs `fortran-indent-subprogram', a command to reindent all the lines of the Fortran subprogram (function or subroutine) containing point. The key `C-M-j' runs `fortran-split-line', which splits a line in the appropriate fashion for Fortran. In a non-comment line, the second half becomes a continuation line and is indented accordingly. In a comment line, both halves become separate comment lines. `M-^' or `C-c C-d' runs the command `fortran-join-line', which joins a continuation line back to the previous line, roughly as the inverse of `fortran-split-line'. The point must be on a continuation line when this command is invoked. `M-q' in Fortran mode fills the comment block or statement that point is in. This removes any excess statement continuations.  File: emacs, Node: ForIndent Cont, Next: ForIndent Num, Prev: ForIndent Commands, Up: Fortran Indent Continuation Lines .................. Most modern Fortran compilers allow two ways of writing continuation lines. If the first non-space character on a line is in column 5, then that line is a continuation of the previous line. We call this "fixed format". (In GNU Emacs we always count columns from 0.) The variable `fortran-continuation-string' specifies what character to put on column 5. A line that starts with a tab character followed by any digit except `0' is also a continuation line. We call this style of continuation "tab format". Fortran mode can make either style of continuation line, but you must specify which one you prefer. The value of the variable `indent-tabs-mode' controls the choice: `nil' for fixed format, and non-`nil' for tab format. You can tell which style is presently in effect by the presence or absence of the string `Tab' in the mode line. If the text on a line starts with the conventional Fortran continuation marker `$', or if it begins with any non-whitespace character in column 5, Fortran mode treats it as a continuation line. When you indent a continuation line with , it converts the line to the current continuation style. When you split a Fortran statement with `C-M-j', the continuation marker on the newline is created according to the continuation style. The setting of continuation style affects several other aspects of editing in Fortran mode. In fixed format mode, the minimum column number for the body of a statement is 6. Lines inside of Fortran blocks that are indented to larger column numbers always use only the space character for whitespace. In tab format mode, the minimum column number for the statement body is 8, and the whitespace before column 8 must always consist of one tab character. When you enter Fortran mode for an existing file, it tries to deduce the proper continuation style automatically from the file contents. The first line that begins with either a tab character or six spaces determines the choice. The variable `fortran-analyze-depth' specifies how many lines to consider (at the beginning of the file); if none of those lines indicates a style, then the variable `fortran-tab-mode-default' specifies the style. If it is `nil', that specifies fixed format, and non-`nil' specifies tab format.  File: emacs, Node: ForIndent Num, Next: ForIndent Conv, Prev: ForIndent Cont, Up: Fortran Indent Line Numbers ............ If a number is the first non-whitespace in the line, Fortran indentation assumes it is a line number and moves it to columns 0 through 4. (Columns always count from 0 in GNU Emacs.) Line numbers of four digits or less are normally indented one space. The variable `fortran-line-number-indent' controls this; it specifies the maximum indentation a line number can have. Line numbers are indented to right-justify them to end in column 4 unless that would require more than this maximum indentation. The default value of the variable is 1. Simply inserting a line number is enough to indent it according to these rules. As each digit is inserted, the indentation is recomputed. To turn off this feature, set the variable `fortran-electric-line-number' to `nil'. Then inserting line numbers is like inserting anything else.  File: emacs, Node: ForIndent Conv, Next: ForIndent Vars, Prev: ForIndent Num, Up: Fortran Indent Syntactic Conventions ..................... Fortran mode assumes that you follow certain conventions that simplify the task of understanding a Fortran program well enough to indent it properly: * Two nested `do' loops never share a `continue' statement. * Fortran keywords such as `if', `else', `then', `do' and others are written without embedded whitespace or line breaks. Fortran compilers generally ignore whitespace outside of string constants, but Fortran mode does not recognize these keywords if they are not contiguous. Constructs such as `else if' or `end do' are acceptable, but the second word should be on the same line as the first and not on a continuation line. If you fail to follow these conventions, the indentation commands may indent some lines unaesthetically. However, a correct Fortran program retains its meaning when reindented even if the conventions are not followed.  File: emacs, Node: ForIndent Vars, Prev: ForIndent Conv, Up: Fortran Indent Variables for Fortran Indentation ................................. Several additional variables control how Fortran indentation works: `fortran-do-indent' Extra indentation within each level of `do' statement (default 3). `fortran-if-indent' Extra indentation within each level of `if' statement (default 3). This value is also used for extra indentation within each level of the Fortran 90 `where' statement. `fortran-structure-indent' Extra indentation within each level of `structure', `union', or `map' statements (default 3). `fortran-continuation-indent' Extra indentation for bodies of continuation lines (default 5). `fortran-check-all-num-for-matching-do' If this is `nil', indentation assumes that each `do' statement ends on a `continue' statement. Therefore, when computing indentation for a statement other than `continue', it can save time by not checking for a `do' statement ending there. If this is non-`nil', indenting any numbered statement must check for a `do' that ends there. The default is `nil'. `fortran-blink-matching-if' If this is `t', indenting an `endif' statement moves the cursor momentarily to the matching `if' statement to show where it is. The default is `nil'. `fortran-minimum-statement-indent-fixed' Minimum indentation for fortran statements when using fixed format continuation line style. Statement bodies are never indented less than this much. The default is 6. `fortran-minimum-statement-indent-tab' Minimum indentation for fortran statements for tab format continuation line style. Statement bodies are never indented less than this much. The default is 8.  File: emacs, Node: Fortran Comments, Next: Fortran Autofill, Prev: Fortran Indent, Up: Fortran Fortran Comments ---------------- The usual Emacs comment commands assume that a comment can follow a line of code. In Fortran, the standard comment syntax requires an entire line to be just a comment. Therefore, Fortran mode replaces the standard Emacs comment commands and defines some new variables. Fortran mode can also handle the Fortran90 comment syntax where comments start with `!' and can follow other text. Because only some Fortran77 compilers accept this syntax, Fortran mode will not insert such comments unless you have said in advance to do so. To do this, set the variable `comment-start' to `"!"' (*note Variables::). `M-;' Align comment or insert new comment (`fortran-comment-indent'). `C-x ;' Applies to nonstandard `!' comments only. `C-c ;' Turn all lines of the region into comments, or (with argument) turn them back into real code (`fortran-comment-region'). `M-;' in Fortran mode is redefined as the command `fortran-comment-indent'. Like the usual `M-;' command, this recognizes any kind of existing comment and aligns its text appropriately; if there is no existing comment, a comment is inserted and aligned. But inserting and aligning comments are not the same in Fortran mode as in other modes. When a new comment must be inserted, if the current line is blank, a full-line comment is inserted. On a non-blank line, a nonstandard `!' comment is inserted if you have said you want to use them. Otherwise a full-line comment is inserted on a new line before the current line. Nonstandard `!' comments are aligned like comments in other languages, but full-line comments are different. In a standard full-line comment, the comment delimiter itself must always appear in column zero. What can be aligned is the text within the comment. You can choose from three styles of alignment by setting the variable `fortran-comment-indent-style' to one of these values: `fixed' Align the text at a fixed column, which is the sum of `fortran-comment-line-extra-indent' and the minimum statement indentation. This is the default. The minimum statement indentation is `fortran-minimum-statement-indent-fixed' for fixed format continuation line style and `fortran-minimum-statement-indent-tab' for tab format style. `relative' Align the text as if it were a line of code, but with an additional `fortran-comment-line-extra-indent' columns of indentation. `nil' Don't move text in full-line comments automatically at all. In addition, you can specify the character to be used to indent within full-line comments by setting the variable `fortran-comment-indent-char' to the single-character string you want to use. Fortran mode introduces two variables `comment-line-start' and `comment-line-start-skip', which play for full-line comments the same roles played by `comment-start' and `comment-start-skip' for ordinary text-following comments. Normally these are set properly by Fortran mode, so you do not need to change them. The normal Emacs comment command `C-x ;' has not been redefined. If you use `!' comments, this command can be used with them. Otherwise it is useless in Fortran mode. The command `C-c ;' (`fortran-comment-region') turns all the lines of the region into comments by inserting the string `C$$$' at the front of each one. With a numeric argument, it turns the region back into live code by deleting `C$$$' from the front of each line in it. The string used for these comments can be controlled by setting the variable `fortran-comment-region'. Note that here we have an example of a command and a variable with the same name; these two uses of the name never conflict because in Lisp and in Emacs it is always clear from the context which one is meant.  File: emacs, Node: Fortran Autofill, Next: Fortran Columns, Prev: Fortran Comments, Up: Fortran Fortran Auto Fill Mode ---------------------- Fortran Auto Fill mode is a minor mode which automatically splits Fortran statements as you insert them when they become too wide. Splitting a statement involves making continuation lines using `fortran-continuation-string' (*note ForIndent Cont::). This splitting happens when you type , , or , and also in the Fortran indentation commands. `M-x fortran-auto-fill-mode' turns Fortran Auto Fill mode on if it was off, or off if it was on. This command works the same as `M-x auto-fill-mode' does for normal Auto Fill mode (*note Filling::). A positive numeric argument turns Fortran Auto Fill mode on, and a negative argument turns it off. You can see when Fortran Auto Fill mode is in effect by the presence of the word `Fill' in the mode line, inside the parentheses. Fortran Auto Fill mode is a minor mode, turned on or off for each buffer individually. *Note Minor Modes::. Fortran Auto Fill mode breaks lines at spaces or delimiters when the lines get longer than the desired width (the value of `fill-column'). The delimiters that Fortran Auto Fill mode may break at are `,', `'', `+', `-', `/', `*', `=', and `)'. The line break comes after the delimiter if the variable `fortran-break-before-delimiters' is `nil'. Otherwise (and by default), the break comes before the delimiter. By default, Fortran Auto Fill mode is not enabled. If you want this feature turned on permanently, add a hook function to `fortran-mode-hook' to execute `(fortran-auto-fill-mode 1)'. *Note Hooks::.  File: emacs, Node: Fortran Columns, Next: Fortran Abbrev, Prev: Fortran Autofill, Up: Fortran Checking Columns in Fortran --------------------------- `C-c C-r' Display a "column ruler" momentarily above the current line (`fortran-column-ruler'). `C-c C-w' Split the current window horizontally temporarily so that it is 72 columns wide (`fortran-window-create-momentarily'). This may help you avoid making lines longer than the 72-character limit that some Fortran compilers impose. `C-u C-c C-w' Split the current window horizontally so that it is 72 columns wide (`fortran-window-create'). You can then continue editing. `M-x fortran-strip-sequence-nos' Delete all text in column 72 and beyond. The command `C-c C-r' (`fortran-column-ruler') shows a column ruler momentarily above the current line. The comment ruler is two lines of text that show you the locations of columns with special significance in Fortran programs. Square brackets show the limits of the columns for line numbers, and curly brackets show the limits of the columns for the statement body. Column numbers appear above them. Note that the column numbers count from zero, as always in GNU Emacs. As a result, the numbers may be one less than those you are familiar with; but the positions they indicate in the line are standard for Fortran. The text used to display the column ruler depends on the value of the variable `indent-tabs-mode'. If `indent-tabs-mode' is `nil', then the value of the variable `fortran-column-ruler-fixed' is used as the column ruler. Otherwise, the variable `fortran-column-ruler-tab' is displayed. By changing these variables, you can change the column ruler display. `C-c C-w' (`fortran-window-create-momentarily') temporarily splits the current window horizontally, making a window 72 columns wide, so you can see which lines that is too long. Type a space to restore the normal width. You can also split the window horizontally and continue editing with the split in place. To do this, use `C-u C-c C-w' (`M-x fortran-window-create'). By editing in this window you can immediately see when you make a line too wide to be correct Fortran. The command `M-x fortran-strip-sequence-nos' deletes all text in column 72 and beyond, on all lines in the current buffer. This is the easiest way to get rid of old sequence numbers.  File: emacs, Node: Fortran Abbrev, Prev: Fortran Columns, Up: Fortran Fortran Keyword Abbrevs ----------------------- Fortran mode provides many built-in abbrevs for common keywords and declarations. These are the same sort of abbrev that you can define yourself. To use them, you must turn on Abbrev mode. *Note Abbrevs::. The built-in abbrevs are unusual in one way: they all start with a semicolon. You cannot normally use semicolon in an abbrev, but Fortran mode makes this possible by changing the syntax of semicolon to "word constituent." For example, one built-in Fortran abbrev is `;c' for `continue'. If you insert `;c' and then insert a punctuation character such as a space or a newline, the `;c' expands automatically to `continue', provided Abbrev mode is enabled. Type `;?' or `;C-h' to display a list of all the built-in Fortran abbrevs and what they stand for.  File: emacs, Node: Asm Mode, Prev: Fortran, Up: Programs Asm Mode ======== Asm mode is a major mode for editing files of assembler code. It defines these commands: `' `tab-to-tab-stop'. `C-j' Insert a newline and then indent using `tab-to-tab-stop'. `:' Insert a colon and then remove the indentation from before the label preceding colon. Then do `tab-to-tab-stop'. `;' Insert or align a comment. The variable `asm-comment-char' specifies which character starts comments in assembler syntax.  File: emacs, Node: Building, Next: Maintaining, Prev: Programs, Up: Top Compiling and Testing Programs ****************************** The previous chapter discusses the Emacs commands that are useful for making changes in programs. This chapter deals with commands that assist in the larger process of developing and maintaining programs. * Menu: * Compilation:: Compiling programs in languages other than Lisp (C, Pascal, etc.). * Grep Searching:: Running grep as if it were a compiler. * Compilation Mode:: The mode for visiting compiler errors. * Compilation Shell:: Customizing your shell properly for use in the compilation buffer. * Debuggers:: Running symbolic debuggers for non-Lisp programs. * Executing Lisp:: Various modes for editing Lisp programs, with different facilities for running the Lisp programs. * Libraries: Lisp Libraries. Creating Lisp programs to run in Emacs. * Interaction: Lisp Interaction. Executing Lisp in an Emacs buffer. * Eval: Lisp Eval. Executing a single Lisp expression in Emacs. * External Lisp:: Communicating through Emacs with a separate Lisp.  File: emacs, Node: Compilation, Next: Grep Searching, Up: Building Running Compilations under Emacs ================================ Emacs can run compilers for noninteractive languages such as C and Fortran as inferior processes, feeding the error log into an Emacs buffer. It can also parse the error messages and show you the source lines where compilation errors occurred. `M-x compile' Run a compiler asynchronously under Emacs, with error messages going to the `*compilation*' buffer. `M-x recompile' Invoke a compiler with the same command as in the last invocation of `M-x compile'. `M-x grep' Run `grep' asynchronously under Emacs, with matching lines listed in the buffer named `*grep*'. `M-x grep-find' Run `grep' via `find', with user-specified arguments, and collect output in the buffer named `*grep*'. `M-x kill-compilation' `M-x kill-grep' Kill the running compilation or `grep' subprocess. To run `make' or another compilation command, do `M-x compile'. This command reads a shell command line using the minibuffer, and then executes the command in an inferior shell, putting output in the buffer named `*compilation*'. The current buffer's default directory is used as the working directory for the execution of the command; normally, therefore, the compilation happens in this directory. When the shell command line is read, the minibuffer appears containing a default command line, which is the command you used the last time you did `M-x compile'. If you type just , the same command line is used again. For the first `M-x compile', the default is `make -k'. The default compilation command comes from the variable `compile-command'; if the appropriate compilation command for a file is something other than `make -k', it can be useful for the file to specify a local value for `compile-command' (*note File Variables::). Starting a compilation displays the buffer `*compilation*' in another window but does not select it. The buffer's mode line tells you whether compilation is finished, with the word `run' or `exit' inside the parentheses. You do not have to keep this buffer visible; compilation continues in any case. While a compilation is going on, the string `Compiling' appears in the mode lines of all windows. When this string disappears, the compilation is finished. If you want to watch the compilation transcript as it appears, switch to the `*compilation*' buffer and move point to the end of the buffer. When point is at the end, new compilation output is inserted above point, which remains at the end. If point is not at the end of the buffer, it remains fixed while more compilation output is added at the end of the buffer. If you set the variable `compilation-scroll-output' to a non-`nil' value, then the compilation buffer always scrolls to follow output as it comes in. To kill the compilation process, do `M-x kill-compilation'. When the compiler process terminates, the mode line of the `*compilation*' buffer changes to say `signal' instead of `run'. Starting a new compilation also kills any running compilation, as only one can exist at any time. However, `M-x compile' asks for confirmation before actually killing a compilation that is running. To rerun the last compilation with the same command, type `M-x recompile'. This automatically reuses the compilation command from the last invocation of `M-x compile'.  File: emacs, Node: Grep Searching, Next: Compilation Mode, Prev: Compilation, Up: Building Searching with Grep under Emacs =============================== Just as you can run a compiler from Emacs and then visit the lines where there were compilation errors, you can also run `grep' and then visit the lines on which matches were found. This works by treating the matches reported by `grep' as if they were "errors." To do this, type `M-x grep', then enter a command line that specifies how to run `grep'. Use the same arguments you would give `grep' when running it normally: a `grep'-style regexp (usually in single-quotes to quote the shell's special characters) followed by file names, which may use wildcards. The output from `grep' goes in the `*grep*' buffer. You can find the corresponding lines in the original files using `C-x `' and , as with compilation errors. If you specify a prefix argument for `M-x grep', it figures out the tag (*note Tags::) around point, and puts that into the default `grep' command. The command `M-x grep-find' is similar to `M-x grep', but it supplies a different initial default for the command--one that runs both `find' and `grep', so as to search every file in a directory tree. See also the `find-grep-dired' command, in *Note Dired and Find::.  File: emacs, Node: Compilation Mode, Next: Compilation Shell, Prev: Grep Searching, Up: Building Compilation Mode ================ The `*compilation*' buffer uses a special major mode, Compilation mode, whose main feature is to provide a convenient way to look at the source line where the error happened. If you set the variable `compilation-scroll-output' to a non-`nil' value, then the compilation buffer always scrolls to follow output as it comes in. `C-x `' Visit the locus of the next compiler error message or `grep' match. `' Visit the locus of the error message that point is on. This command is used in the compilation buffer. `Mouse-2' Visit the locus of the error message that you click on. You can visit the source for any particular error message by moving point in the `*compilation*' buffer to that error message and typing (`compile-goto-error'). Alternatively, you can click `Mouse-2' on the error message; you need not switch to the `*compilation*' buffer first. To parse the compiler error messages sequentially, type `C-x `' (`next-error'). The character following the `C-x' is the backquote or "grave accent," not the single-quote. This command is available in all buffers, not just in `*compilation*'; it displays the next error message at the top of one window and source location of the error in another window. The first time `C-x `' is used after the start of a compilation, it moves to the first error's location. Subsequent uses of `C-x `' advance down to subsequent errors. If you visit a specific error message with or `Mouse-2', subsequent `C-x `' commands advance from there. When `C-x `' gets to the end of the buffer and finds no more error messages to visit, it fails and signals an Emacs error. `C-u C-x `' starts scanning from the beginning of the compilation buffer. This is one way to process the same set of errors again. To parse messages from the compiler, Compilation mode uses the variable `compilation-error-regexp-alist' which lists various formats of error messages and tells Emacs how to extract the source file and the line number from the text of a message. If your compiler isn't supported, you can tailor Compilation mode to it by adding elements to that list. A similar variable `grep-regexp-alist' tells Emacs how to parse output of a `grep' command. Compilation mode also redefines the keys and to scroll by screenfuls, and `M-n' and `M-p' to move to the next or previous error message. You can also use `M-{' and `M-}' to move up or down to an error message for a different source file. The features of Compilation mode are also available in a minor mode called Compilation Minor mode. This lets you parse error messages in any buffer, not just a normal compilation output buffer. Type `M-x compilation-minor-mode' to enable the minor mode. This defines the keys and `Mouse-2', as in the Compilation major mode. Compilation minor mode works in any buffer, as long as the contents are in a format that it understands. In an Rlogin buffer (*note Remote Host::), Compilation minor mode automatically accesses remote source files by FTP (*note File Names::).  File: emacs, Node: Compilation Shell, Next: Debuggers, Prev: Compilation Mode, Up: Building Subshells for Compilation ========================= Emacs uses a shell to run the compilation command, but specifies the option for a noninteractive shell. This means, in particular, that the shell should start with no prompt. If you find your usual shell prompt making an unsightly appearance in the `*compilation*' buffer, it means you have made a mistake in your shell's init file by setting the prompt unconditionally. (This init file's name may be `.bashrc', `.profile', `.cshrc', `.shrc', or various other things, depending on the shell you use.) The shell init file should set the prompt only if there already is a prompt. In csh, here is how to do it: if ($?prompt) set prompt = ... And here's how to do it in bash: if [ "${PS1+set}" = set ] then PS1=... fi There may well be other things that your shell's init file ought to do only for an interactive shell. You can use the same method to conditionalize them. The MS-DOS "operating system" does not support asynchronous subprocesses; to work around this lack, `M-x compile' runs the compilation command synchronously on MS-DOS. As a consequence, you must wait until the command finishes before you can do anything else in Emacs. *Note MS-DOS::.  File: emacs, Node: Debuggers, Next: Executing Lisp, Prev: Compilation Shell, Up: Building Running Debuggers Under Emacs ============================= The GUD (Grand Unified Debugger) library provides an interface to various symbolic debuggers from within Emacs. We recommend the debugger GDB, which is free software, but you can also run DBX, SDB or XDB if you have them. GUD can also serve as an interface to the Perl's debugging mode, the Python debugger PDB, and to JDB, the Java Debugger. *Note The Lisp Debugger: (elisp)Debugger, for information on debugging Emacs Lisp programs. * Menu: * Starting GUD:: How to start a debugger subprocess. * Debugger Operation:: Connection between the debugger and source buffers. * Commands of GUD:: Key bindings for common commands. * GUD Customization:: Defining your own commands for GUD. * GUD Tooltips:: Showing variable values by pointing with the mouse.  File: emacs, Node: Starting GUD, Next: Debugger Operation, Up: Debuggers Starting GUD ------------ There are several commands for starting a debugger, each corresponding to a particular debugger program. `M-x gdb FILE ' Run GDB as a subprocess of Emacs. This command creates a buffer for input and output to GDB, and switches to it. If a GDB buffer already exists, it just switches to that buffer. `M-x dbx FILE ' Similar, but run DBX instead of GDB. `M-x xdb FILE ' Similar, but run XDB instead of GDB. Use the variable `gud-xdb-directories' to specify directories to search for source files. `M-x sdb FILE ' Similar, but run SDB instead of GDB. Some versions of SDB do not mention source file names in their messages. When you use them, you need to have a valid tags table (*note Tags::) in order for GUD to find functions in the source code. If you have not visited a tags table or the tags table doesn't list one of the functions, you get a message saying `The sdb support requires a valid tags table to work'. If this happens, generate a valid tags table in the working directory and try again. `M-x perldb FILE ' Run the Perl interpreter in debug mode to debug FILE, a Perl program. `M-x jdb FILE ' Run the Java debugger to debug FILE. `M-x pdb FILE ' Run the Python debugger to debug FILE. Each of these commands takes one argument: a command line to invoke the debugger. In the simplest case, specify just the name of the executable file you want to debug. You may also use options that the debugger supports. However, shell wildcards and variables are not allowed. GUD assumes that the first argument not starting with a `-' is the executable file name. Emacs can only run one debugger process at a time.  File: emacs, Node: Debugger Operation, Next: Commands of GUD, Prev: Starting GUD, Up: Debuggers Debugger Operation ------------------ When you run a debugger with GUD, the debugger uses an Emacs buffer for its ordinary input and output. This is called the GUD buffer. The debugger displays the source files of the program by visiting them in Emacs buffers. An arrow (`=>') in one of these buffers indicates the current execution line.(1) Moving point in this buffer does not move the arrow. You can start editing these source files at any time in the buffers that display them. The arrow is not part of the file's text; it appears only on the screen. If you do modify a source file, keep in mind that inserting or deleting lines will throw off the arrow's positioning; GUD has no way of figuring out which line corresponded before your changes to the line number in a debugger message. Also, you'll typically have to recompile and restart the program for your changes to be reflected in the debugger's tables. If you wish, you can control your debugger process entirely through the debugger buffer, which uses a variant of Shell mode. All the usual commands for your debugger are available, and you can use the Shell mode history commands to repeat them. *Note Shell Mode::. ---------- Footnotes ---------- (1) Under a window system the arrow is displayed in the marginal area of the Emacs window.  File: emacs, Node: Commands of GUD, Next: GUD Customization, Prev: Debugger Operation, Up: Debuggers Commands of GUD --------------- The GUD interaction buffer uses a variant of Shell mode, so the commands of Shell mode are available (*note Shell Mode::). GUD mode also provides commands for setting and clearing breakpoints, for selecting stack frames, and for stepping through the program. These commands are available both in the GUD buffer and globally, but with different key bindings. The breakpoint commands are normally used in source file buffers, because that is the easiest way to specify where to set or clear the breakpoint. Here's the global command to set a breakpoint: `C-x ' Set a breakpoint on the source line that point is on. Here are the other special commands provided by GUD. The keys starting with `C-c' are available only in the GUD interaction buffer. The key bindings that start with `C-x C-a' are available in the GUD interaction buffer and also in source files. `C-c C-l' `C-x C-a C-l' Display in another window the last line referred to in the GUD buffer (that is, the line indicated in the last location message). This runs the command `gud-refresh'. `C-c C-s' `C-x C-a C-s' Execute a single line of code (`gud-step'). If the line contains a function call, execution stops after entering the called function. `C-c C-n' `C-x C-a C-n' Execute a single line of code, stepping across entire function calls at full speed (`gud-next'). `C-c C-i' `C-x C-a C-i' Execute a single machine instruction (`gud-stepi'). `C-c C-r' `C-x C-a C-r' Continue execution without specifying any stopping point. The program will run until it hits a breakpoint, terminates, or gets a signal that the debugger is checking for (`gud-cont'). `C-c C-d' `C-x C-a C-d' Delete the breakpoint(s) on the current source line, if any (`gud-remove'). If you use this command in the GUD interaction buffer, it applies to the line where the program last stopped. `C-c C-t' `C-x C-a C-t' Set a temporary breakpoint on the current source line, if any. If you use this command in the GUD interaction buffer, it applies to the line where the program last stopped. The above commands are common to all supported debuggers. If you are using GDB or (some versions of) DBX, these additional commands are available: `C-c <' `C-x C-a <' Select the next enclosing stack frame (`gud-up'). This is equivalent to the `up' command. `C-c >' `C-x C-a >' Select the next inner stack frame (`gud-down'). This is equivalent to the `down' command. If you are using GDB, these additional key bindings are available: `' With GDB, complete a symbol name (`gud-gdb-complete-command'). This key is available only in the GUD interaction buffer, and requires GDB versions 4.13 and later. `C-c C-f' `C-x C-a C-f' Run the program until the selected stack frame returns (or until it stops for some other reason). These commands interpret a numeric argument as a repeat count, when that makes sense. Because serves as a completion command, you can't use it to enter a tab as input to the program you are debugging with GDB. Instead, type `C-q ' to enter a tab.  File: emacs, Node: GUD Customization, Next: GUD Tooltips, Prev: Commands of GUD, Up: Debuggers GUD Customization ----------------- On startup, GUD runs one of the following hooks: `gdb-mode-hook', if you are using GDB; `dbx-mode-hook', if you are using DBX; `sdb-mode-hook', if you are using SDB; `xdb-mode-hook', if you are using XDB; `perldb-mode-hook', for Perl debugging mode; `pdb-mode-hook', for PDB; `jdb-mode-hook', for JDB. You can use these hooks to define custom key bindings for the debugger interaction buffer. *Note Hooks::. Here is a convenient way to define a command that sends a particular command string to the debugger, and set up a key binding for it in the debugger interaction buffer: (gud-def FUNCTION CMDSTRING BINDING DOCSTRING) This defines a command named FUNCTION which sends CMDSTRING to the debugger process, and gives it the documentation string DOCSTRING. You can then use the command FUNCTION in any buffer. If BINDING is non-`nil', `gud-def' also binds the command to `C-c BINDING' in the GUD buffer's mode and to `C-x C-a BINDING' generally. The command string CMDSTRING may contain certain `%'-sequences that stand for data to be filled in at the time FUNCTION is called: `%f' The name of the current source file. If the current buffer is the GUD buffer, then the "current source file" is the file that the program stopped in. `%l' The number of the current source line. If the current buffer is the GUD buffer, then the "current source line" is the line that the program stopped in. `%e' The text of the C lvalue or function-call expression at or adjacent to point. `%a' The text of the hexadecimal address at or adjacent to point. `%p' The numeric argument of the called function, as a decimal number. If the command is used without a numeric argument, `%p' stands for the empty string. If you don't use `%p' in the command string, the command you define ignores any numeric argument.  File: emacs, Node: GUD Tooltips, Prev: GUD Customization, Up: Debuggers GUD Tooltips ------------ The Tooltip facility (*note Tooltips::) provides support for GUD. If GUD support is activated by customizing the `tooltip' group, variable values can be displayed in tooltips by pointing at them with the mouse in the GUD buffer or in source buffers with major modes in the customizable list `tooltip-gud-modes'.  File: emacs, Node: Executing Lisp, Next: Lisp Libraries, Prev: Debuggers, Up: Building Executing Lisp Expressions ========================== Emacs has several different major modes for Lisp and Scheme. They are the same in terms of editing commands, but differ in the commands for executing Lisp expressions. Each mode has its own purpose. Emacs-Lisp mode The mode for editing source files of programs to run in Emacs Lisp. This mode defines `C-M-x' to evaluate the current defun. *Note Lisp Libraries::. Lisp Interaction mode The mode for an interactive session with Emacs Lisp. It defines `C-j' to evaluate the sexp before point and insert its value in the buffer. *Note Lisp Interaction::. Lisp mode The mode for editing source files of programs that run in Lisps other than Emacs Lisp. This mode defines `C-M-x' to send the current defun to an inferior Lisp process. *Note External Lisp::. Inferior Lisp mode The mode for an interactive session with an inferior Lisp process. This mode combines the special features of Lisp mode and Shell mode (*note Shell Mode::). Scheme mode Like Lisp mode but for Scheme programs. Inferior Scheme mode The mode for an interactive session with an inferior Scheme process. Most editing commands for working with Lisp programs are in fact available globally. *Note Programs::.  File: emacs, Node: Lisp Libraries, Next: Lisp Interaction, Prev: Executing Lisp, Up: Building Libraries of Lisp Code for Emacs ================================ Lisp code for Emacs editing commands is stored in files whose names conventionally end in `.el'. This ending tells Emacs to edit them in Emacs-Lisp mode (*note Executing Lisp::). To execute a file of Emacs Lisp code, use `M-x load-file'. This command reads a file name using the minibuffer and then executes the contents of that file as Lisp code. It is not necessary to visit the file first; in any case, this command reads the file as found on disk, not text in an Emacs buffer. Once a file of Lisp code is installed in the Emacs Lisp library directories, users can load it using `M-x load-library'. Programs can load it by calling `load-library', or with `load', a more primitive function that is similar but accepts some additional arguments. `M-x load-library' differs from `M-x load-file' in that it searches a sequence of directories and tries three file names in each directory. Suppose your argument is LIB; the three names are `LIB.elc', `LIB.el', and lastly just `LIB'. If `LIB.elc' exists, it is by convention the result of compiling `LIB.el'; it is better to load the compiled file, since it will load and run faster. If `load-library' finds that `LIB.el' is newer than `LIB.elc' file, it issues a warning, because it's likely that somebody made changes to the `.el' file and forgot to recompile it. Because the argument to `load-library' is usually not in itself a valid file name, file name completion is not available. Indeed, when using this command, you usually do not know exactly what file name will be used. The sequence of directories searched by `M-x load-library' is specified by the variable `load-path', a list of strings that are directory names. The default value of the list contains the directory where the Lisp code for Emacs itself is stored. If you have libraries of your own, put them in a single directory and add that directory to `load-path'. `nil' in this list stands for the current default directory, but it is probably not a good idea to put `nil' in the list. If you find yourself wishing that `nil' were in the list, most likely what you really want to do is use `M-x load-file' this once. Often you do not have to give any command to load a library, because the commands defined in the library are set up to "autoload" that library. Trying to run any of those commands calls `load' to load the library; this replaces the autoload definitions with the real ones from the library. Emacs Lisp code can be compiled into byte-code which loads faster, takes up less space when loaded, and executes faster. *Note Byte Compilation: (elisp)Byte Compilation. By convention, the compiled code for a library goes in a separate file whose name consists of the library source file with `c' appended. Thus, the compiled code for `foo.el' goes in `foo.elc'. That's why `load-library' searches for `.elc' files first. By default, Emacs refuses to load compiled Lisp files which were compiled with XEmacs, a modified versions of Emacs--they can cause Emacs to crash. Set the variable `load-dangerous-libraries' to `t' if you want to try loading them.