This is ../info/xemacs.info, produced by makeinfo version 4.0 from xemacs/xemacs.texi. INFO-DIR-SECTION XEmacs Editor START-INFO-DIR-ENTRY * XEmacs: (xemacs). XEmacs Editor. END-INFO-DIR-ENTRY This file documents the XEmacs editor. Copyright (C) 1985, 1986, 1988 Richard M. Stallman. Copyright (C) 1991, 1992, 1993, 1994 Lucid, Inc. Copyright (C) 1993, 1994 Sun Microsystems, Inc. Copyright (C) 1995 Amdahl Corporation. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" are included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" may be included in a translation approved by the author instead of in the original English. File: xemacs.info, Node: Basic Indent, Next: Multi-line Indent, Prev: Grinding, Up: Grinding Basic Program Indentation Commands ---------------------------------- `' Adjust indentation of current line. `' Equivalent to followed by (`newline-and-indent'). The basic indentation command is , which gives the current line the correct indentation as determined from the previous lines. The function that runs depends on the major mode; it is `lisp-indent-line' in Lisp mode, `c-indent-line' in C mode, etc. These functions understand different syntaxes for different languages, but they all do about the same thing. in any programming language major mode inserts or deletes whitespace at the beginning of the current line, independent of where point is in the line. If point is inside the whitespace at the beginning of the line, leaves it at the end of that whitespace; otherwise, leaves point fixed with respect to the characters around it. Use `C-q ' to insert a tab at point. When entering a large amount of new code, use (`newline-and-indent'), which is equivalent to a followed by a . creates a blank line, then gives it the appropriate indentation. indents the second and following lines of the body of a parenthetical grouping each under the preceding one; therefore, if you alter one line's indentation to be nonstandard, the lines below tend to follow it. This is the right behavior in cases where the standard result of does not look good. Remember that Emacs assumes that an open-parenthesis, open-brace, or other opening delimiter at the left margin (including the indentation routines) is the start of a function. You should therefore never have an opening delimiter in column zero that is not the beginning of a function, not even inside a string. This restriction is vital for making the indentation commands fast. *Note Defuns::, for more information on this behavior. File: xemacs.info, Node: Multi-line Indent, Next: Lisp Indent, Prev: Basic Indent, Up: Grinding Indenting Several Lines ----------------------- Several commands are available to re-indent several lines of code which have been altered or moved to a different level in a list structure. `C-M-q' Re-indent all the lines within one list (`indent-sexp'). `C-u ' Shift an entire list rigidly sideways so that its first line is properly indented. `C-M-\' Re-indent all lines in the region (`indent-region'). To re-indent the contents of a single list, position point before the beginning of it and type `C-M-q'. This key is bound to `indent-sexp' in Lisp mode, `indent-c-exp' in C mode, and bound to other suitable functions in other modes. The indentation of the line the sexp starts on is not changed; therefore, only the relative indentation within the list, and not its position, is changed. To correct the position as well, type a before `C-M-q'. If the relative indentation within a list is correct but the indentation of its beginning is not, go to the line on which the list begins and type `C-u '. When you give a numeric argument, it moves all the lines in the group, starting on the current line, sideways the same amount that the current line moves. The command does not move lines that start inside strings, or C preprocessor lines when in C mode. Another way to specify a range to be re-indented is with point and mark. The command `C-M-\' (`indent-region') applies to every line whose first character is between point and mark. File: xemacs.info, Node: Lisp Indent, Next: C Indent, Prev: Multi-line Indent, Up: Grinding Customizing Lisp Indentation ---------------------------- The indentation pattern for a Lisp expression can depend on the function called by the expression. For each Lisp function, you can choose among several predefined patterns of indentation, or define an arbitrary one with a Lisp program. The standard pattern of indentation is as follows: the second line of the expression is indented under the first argument, if that is on the same line as the beginning of the expression; otherwise, the second line is indented underneath the function name. Each following line is indented under the previous line whose nesting depth is the same. If the variable `lisp-indent-offset' is non-`nil', it overrides the usual indentation pattern for the second line of an expression, so that such lines are always indented `lisp-indent-offset' more columns than the containing list. Certain functions override the standard pattern. Functions whose names start with `def' always indent the second line by `lisp-body-indention' extra columns beyond the open-parenthesis starting the expression. Individual functions can override the standard pattern in various ways, according to the `lisp-indent-function' property of the function name. (Note: `lisp-indent-function' was formerly called `lisp-indent-hook'). There are four possibilities for this property: `nil' This is the same as no property; the standard indentation pattern is used. `defun' The pattern used for function names that start with `def' is used for this function also. a number, NUMBER The first NUMBER arguments of the function are "distinguished" arguments; the rest are considered the "body" of the expression. A line in the expression is indented according to whether the first argument on it is distinguished or not. If the argument is part of the body, the line is indented `lisp-body-indent' more columns than the open-parenthesis starting the containing expression. If the argument is distinguished and is either the first or second argument, it is indented twice that many extra columns. If the argument is distinguished and not the first or second argument, the standard pattern is followed for that line. a symbol, SYMBOL SYMBOL should be a function name; that function is called to calculate the indentation of a line within this expression. The function receives two arguments: STATE The value returned by `parse-partial-sexp' (a Lisp primitive for indentation and nesting computation) when it parses up to the beginning of this line. POS The position at which the line being indented begins. It should return either a number, which is the number of columns of indentation for that line, or a list whose first element is such a number. The difference between returning a number and returning a list is that a number says that all following lines at the same nesting level should be indented just like this one; a list says that following lines might call for different indentations. This makes a difference when the indentation is computed by `C-M-q'; if the value is a number, `C-M-q' need not recalculate indentation for the following lines until the end of the list. File: xemacs.info, Node: C Indent, Prev: Lisp Indent, Up: Grinding Customizing C Indentation ------------------------- Two variables control which commands perform C indentation and when. If `c-auto-newline' is non-`nil', newlines are inserted both before and after braces that you insert and after colons and semicolons. Correct C indentation is done on all the lines that are made this way. If `c-tab-always-indent' is non-`nil', the command in C mode does indentation only if point is at the left margin or within the line's indentation. If there is non-whitespace to the left of point, just inserts a tab character in the buffer. Normally, this variable is `nil', and always reindents the current line. C does not have anything analogous to particular function names for which special forms of indentation are desirable. However, it has a different need for customization facilities: many different styles of C indentation are in common use. There are six variables you can set to control the style that Emacs C mode will use. `c-indent-level' Indentation of C statements within surrounding block. The surrounding block's indentation is the indentation of the line on which the open-brace appears. `c-continued-statement-offset' Extra indentation given to a substatement, such as the then-clause of an `if' or body of a `while'. `c-brace-offset' Extra indentation for lines that start with an open brace. `c-brace-imaginary-offset' An open brace following other text is treated as if it were this far to the right of the start of its line. `c-argdecl-indent' Indentation level of declarations of C function arguments. `c-label-offset' Extra indentation for a line that is a label, case, or default. The variable `c-indent-level' controls the indentation for C statements with respect to the surrounding block. In the example: { foo (); the difference in indentation between the lines is `c-indent-level'. Its standard value is 2. If the open-brace beginning the compound statement is not at the beginning of its line, the `c-indent-level' is added to the indentation of the line, not the column of the open-brace. For example, if (losing) { do_this (); One popular indentation style is that which results from setting `c-indent-level' to 8 and putting open-braces at the end of a line in this way. Another popular style prefers to put the open-brace on a separate line. In fact, the value of the variable `c-brace-imaginary-offset' is also added to the indentation of such a statement. Normally this variable is zero. Think of this variable as the imaginary position of the open brace, relative to the first non-blank character on the line. By setting the variable to 4 and `c-indent-level' to 0, you can get this style: if (x == y) { do_it (); } When `c-indent-level' is zero, the statements inside most braces line up exactly under the open brace. An exception are braces in column zero, like those surrounding a function's body. The statements inside those braces are not placed at column zero. Instead, `c-brace-offset' and `c-continued-statement-offset' (see below) are added to produce a typical offset between brace levels, and the statements are indented that far. `c-continued-statement-offset' controls the extra indentation for a line that starts within a statement (but not within parentheses or brackets). These lines are usually statements inside other statements, like the then-clauses of `if' statements and the bodies of `while' statements. The `c-continued-statement-offset' parameter determines the difference in indentation between the two lines in: if (x == y) do_it (); The default value for `c-continued-statement-offset' is 2. Some popular indentation styles correspond to a value of zero for `c-continued-statement-offset'. `c-brace-offset' is the extra indentation given to a line that starts with an open-brace. Its standard value is zero; compare: if (x == y) { with: if (x == y) do_it (); If you set `c-brace-offset' to 4, the first example becomes: if (x == y) { `c-argdecl-indent' controls the indentation of declarations of the arguments of a C function. It is absolute: argument declarations receive exactly `c-argdecl-indent' spaces. The standard value is 5 and results in code like this: char * index (string, char) char *string; int char; `c-label-offset' is the extra indentation given to a line that contains a label, a case statement, or a `default:' statement. Its standard value is -2 and results in code like this: switch (c) { case 'x': If `c-label-offset' were zero, the same code would be indented as: switch (c) { case 'x': This example assumes that the other variables above also have their default values. Using the indentation style produced by the default settings of the variables just discussed and putting open braces on separate lines produces clear and readable files. For an example, look at any of the C source files of XEmacs. File: xemacs.info, Node: Matching, Next: Comments, Prev: Grinding, Up: Programs Automatic Display of Matching Parentheses ========================================= The Emacs parenthesis-matching feature shows you automatically how parentheses match in the text. Whenever a self-inserting character that is a closing delimiter is typed, the cursor moves momentarily to the location of the matching opening delimiter, provided that is visible on the screen. If it is not on the screen, some text starting with that opening delimiter is displayed in the echo area. Either way, you see the grouping you are closing off. In Lisp, automatic matching applies only to parentheses. In C, it also applies to braces and brackets. Emacs knows which characters to regard as matching delimiters based on the syntax table set by the major mode. *Note Syntax::. If the opening delimiter and closing delimiter are mismatched--as in `[x)'--the echo area displays a warning message. The correct matches are specified in the syntax table. Two variables control parenthesis matching displays. `blink-matching-paren' turns the feature on or off. The default is `t' (match display is on); `nil' turns it off. `blink-matching-paren-distance' specifies how many characters back Emacs searches to find a matching opening delimiter. If the match is not found in the specified region, scanning stops, and nothing is displayed. This prevents wasting lots of time scanning when there is no match. The default is 4000. File: xemacs.info, Node: Comments, Next: Balanced Editing, Prev: Matching, Up: Programs Manipulating Comments ===================== The comment commands insert, kill and align comments. `M-;' Insert or align comment (`indent-for-comment'). `C-x ;' Set comment column (`set-comment-column'). `C-u - C-x ;' Kill comment on current line (`kill-comment'). `M-' Like followed by inserting and aligning a comment (`indent-new-comment-line'). The command that creates a comment is `Meta-;' (`indent-for-comment'). If there is no comment already on the line, a new comment is created and aligned at a specific column called the "comment column". Emacs creates the comment by inserting the string at the value of `comment-start'; see below. Point is left after that string. If the text of the line extends past the comment column, indentation is done to a suitable boundary (usually, at least one space is inserted). If the major mode has specified a string to terminate comments, that string is inserted after point, to keep the syntax valid. You can also use `Meta-;' to align an existing comment. If a line already contains the string that starts comments, `M-;' just moves point after it and re-indents it to the conventional place. Exception: comments starting in column 0 are not moved. Some major modes have special rules for indenting certain kinds of comments in certain contexts. For example, in Lisp code, comments which start with two semicolons are indented as if they were lines of code, instead of at the comment column. Comments which start with three semicolons are supposed to start at the left margin. Emacs understands these conventions by indenting a double-semicolon comment using and by not changing the indentation of a triple-semicolon comment at all. ;; This function is just an example. ;;; Here either two or three semicolons are appropriate. (defun foo (x) ;;; And now, the first part of the function: ;; The following line adds one. (1+ x)) ; This line adds one. In C code, a comment preceded on its line by nothing but whitespace is indented like a line of code. Even when an existing comment is properly aligned, `M-;' is still useful for moving directly to the start of the comment. `C-u - C-x ;' (`kill-comment') kills the comment on the current line, if there is one. The indentation before the start of the comment is killed as well. If there does not appear to be a comment in the line, nothing happens. To reinsert the comment on another line, move to the end of that line, type first `C-y', and then `M-;' to realign the comment. Note that `C-u - C-x ;' is not a distinct key; it is `C-x ;' (`set-comment-column') with a negative argument. That command is programmed to call `kill-comment' when called with a negative argument. However, `kill-comment' is a valid command which you could bind directly to a key if you wanted to. Multiple Lines of Comments -------------------------- If you are typing a comment and want to continue it on another line, use the command `Meta-' (`indent-new-comment-line'), which terminates the comment you are typing, creates a new blank line afterward, and begins a new comment indented under the old one. If Auto Fill mode is on and you go past the fill column while typing, the comment is continued in just this fashion. If point is not at the end of the line when you type `M-', the text on the rest of the line becomes part of the new comment line. Options Controlling Comments ---------------------------- The comment column is stored in the variable `comment-column'. You can explicitly set it to a number. Alternatively, the command `C-x ;' (`set-comment-column') sets the comment column to the column point is at. `C-u C-x ;' sets the comment column to match the last comment before point in the buffer, and then calls `Meta-;' to align the current line's comment under the previous one. Note that `C-u - C-x ;' runs the function `kill-comment' as described above. `comment-column' is a per-buffer variable; altering the variable affects only the current buffer. You can also change the default value. *Note Locals::. Many major modes initialize this variable for the current buffer. The comment commands recognize comments based on the regular expression that is the value of the variable `comment-start-skip'. This regexp should not match the null string. It may match more than the comment starting delimiter in the strictest sense of the word; for example, in C mode the value of the variable is `"/\\*+ *"', which matches extra stars and spaces after the `/*' itself. (Note that `\\' is needed in Lisp syntax to include a `\' in the string, which is needed to deny the first star its special meaning in regexp syntax. *Note Regexps::.) When a comment command makes a new comment, it inserts the value of `comment-start' to begin it. The value of `comment-end' is inserted after point and will follow the text you will insert into the comment. In C mode, `comment-start' has the value `"/* "' and `comment-end' has the value `" */"'. `comment-multi-line' controls how `M-' (`indent-new-comment-line') behaves when used inside a comment. If `comment-multi-line' is `nil', as it normally is, then `M-' terminates the comment on the starting line and starts a new comment on the new following line. If `comment-multi-line' is not `nil', then `M-' sets up the new following line as part of the same comment that was found on the starting line. This is done by not inserting a terminator on the old line and not inserting a starter on the new line. In languages where multi-line comments are legal, the value you choose for this variable is a matter of taste. The variable `comment-indent-hook' should contain a function that is called to compute the indentation for a newly inserted comment or for aligning an existing comment. Major modes set this variable differently. The function is called with no arguments, but with point at the beginning of the comment, or at the end of a line if a new comment is to be inserted. The function should return the column in which the comment ought to start. For example, in Lisp mode, the indent hook function bases its decision on the number of semicolons that begin an existing comment and on the code in the preceding lines. File: xemacs.info, Node: Balanced Editing, Next: Lisp Completion, Prev: Comments, Up: Programs Editing Without Unbalanced Parentheses ====================================== `M-(' Put parentheses around next sexp(s) (`insert-parentheses'). `M-)' Move past next close parenthesis and re-indent (`move-over-close-and-reindent'). The commands `M-(' (`insert-parentheses') and `M-)' (`move-over-close-and-reindent') are designed to facilitate a style of editing which keeps parentheses balanced at all times. `M-(' inserts a pair of parentheses, either together as in `()', or, if given an argument, around the next several sexps, and leaves point after the open parenthesis. Instead of typing `( F O O )', you can type `M-( F O O', which has the same effect except for leaving the cursor before the close parenthesis. You can then type `M-)', which moves past the close parenthesis, deletes any indentation preceding it (in this example there is none), and indents with after it. File: xemacs.info, Node: Lisp Completion, Next: Documentation, Prev: Balanced Editing, Up: Programs Completion for Lisp Symbols =========================== Completion usually happens in the minibuffer. An exception is completion for Lisp symbol names, which is available in all buffers. The command `M-' (`lisp-complete-symbol') takes the partial Lisp symbol before point to be an abbreviation, and compares it against all non-trivial Lisp symbols currently known to Emacs. Any additional characters that they all have in common are inserted at point. Non-trivial symbols are those that have function definitions, values, or properties. If there is an open-parenthesis immediately before the beginning of the partial symbol, only symbols with function definitions are considered as completions. If the partial name in the buffer has more than one possible completion and they have no additional characters in common, a list of all possible completions is displayed in another window. File: xemacs.info, Node: Documentation, Next: Change Log, Prev: Lisp Completion, Up: Programs Documentation Commands ====================== As you edit Lisp code to be run in Emacs, you can use the commands `C-h f' (`describe-function') and `C-h v' (`describe-variable') to print documentation of functions and variables you want to call. These commands use the minibuffer to read the name of a function or variable to document, and display the documentation in a window. For extra convenience, these commands provide default arguments based on the code in the neighborhood of point. `C-h f' sets the default to the function called in the innermost list containing point. `C-h v' uses the symbol name around or adjacent to point as its default. The `M-x manual-entry' command gives you access to documentation on Unix commands, system calls, and libraries. The command reads a topic as an argument, and displays the Unix manual page for that topic. `manual-entry' always searches all 8 sections of the manual and concatenates all the entries it finds. For example, the topic `termcap' finds the description of the termcap library from section 3, followed by the description of the termcap data base from section 5. File: xemacs.info, Node: Change Log, Next: Tags, Prev: Documentation, Up: Programs Change Logs =========== The Emacs command `M-x add-change-log-entry' helps you keep a record of when and why you have changed a program. It assumes that you have a file in which you write a chronological sequence of entries describing individual changes. The default is to store the change entries in a file called `ChangeLog' in the same directory as the file you are editing. The same `ChangeLog' file therefore records changes for all the files in a directory. A change log entry starts with a header line that contains your name and the current date. Except for these header lines, every line in the change log starts with a tab. One entry can describe several changes; each change starts with a line starting with a tab and a star. `M-x add-change-log-entry' visits the change log file and creates a new entry unless the most recent entry is for today's date and your name. In either case, it adds a new line to start the description of another change just after the header line of the entry. When `M-x add-change-log-entry' is finished, all is prepared for you to edit in the description of what you changed and how. You must then save the change log file yourself. The change log file is always visited in Indented Text mode, which means that and auto-filling indent each new line like the previous line. This is convenient for entering the contents of an entry, which must be indented. *Note Text Mode::. Here is an example of the formatting conventions used in the change log for Emacs: Wed Jun 26 19:29:32 1985 Richard M. Stallman (rms at mit-prep) * xdisp.c (try_window_id): If C-k is done at end of next-to-last line, this fn updates window_end_vpos and cannot leave window_end_pos nonnegative (it is zero, in fact). If display is preempted before lines are output, this is inconsistent. Fix by setting blank_end_of_window to nonzero. Tue Jun 25 05:25:33 1985 Richard M. Stallman (rms at mit-prep) * cmds.c (Fnewline): Call the auto fill hook if appropriate. * xdisp.c (try_window_id): If point is found by compute_motion after xp, record that permanently. If display_text_line sets point position wrong (case where line is killed, point is at eob and that line is not displayed), set it again in final compute_motion. File: xemacs.info, Node: Tags, Next: Fortran, Prev: Change Log, Up: Programs Tags Tables =========== A "tags table" is a description of how a multi-file program is broken up into files. It lists the names of the component files and the names and positions of the functions (or other named subunits) in each file. Grouping the related files makes it possible to search or replace through all the files with one command. Recording the function names and positions makes possible the `M-.' command which finds the definition of a function by looking up which of the files it is in. Tags tables are stored in files called "tags table files". The conventional name for a tags table file is `TAGS'. Each entry in the tags table records the name of one tag, the name of the file that the tag is defined in (implicitly), and the position in that file of the tag's definition. Just what names from the described files are recorded in the tags table depends on the programming language of the described file. They normally include all functions and subroutines, and may also include global variables, data types, and anything else convenient. Each name recorded is called a "tag". * Menu: * Tag Syntax:: Tag syntax for various types of code and text files. * Create Tags Table:: Creating a tags table with `etags'. * Etags Regexps:: Create arbitrary tags using regular expressions. * Select Tags Table:: How to visit a tags table. * Find Tag:: Commands to find the definition of a specific tag. * Tags Search:: Using a tags table for searching and replacing. * List Tags:: Listing and finding tags defined in a file. File: xemacs.info, Node: Tag Syntax, Next: Create Tags Table, Prev: Tags, Up: Tags Source File Tag Syntax ---------------------- Here is how tag syntax is defined for the most popular languages: * In C code, any C function or typedef is a tag, and so are definitions of `struct', `union' and `enum'. You can tag function declarations and external variables in addition to function definitions by giving the `--declarations' option to `etags'. `#define' macro definitions and `enum' constants are also tags, unless you specify `--no-defines' when making the tags table. Similarly, global variables are tags, unless you specify `--no-globals'. Use of `--no-globals' and `--no-defines' can make the tags table file much smaller. * In C++ code, in addition to all the tag constructs of C code, member functions are also recognized, and optionally member variables if you use the `--members' option. Tags for variables and functions in classes are named `CLASS::VARIABLE' and `CLASS::FUNCTION'. `operator' functions tags are named, for example `operator+'. * In Java code, tags include all the constructs recognized in C++, plus the `interface', `extends' and `implements' constructs. Tags for variables and functions in classes are named `CLASS.VARIABLE' and `CLASS.FUNCTION'. * In LaTeX text, the argument of any of the commands `\chapter', `\section', `\subsection', `\subsubsection', `\eqno', `\label', `\ref', `\cite', `\bibitem', `\part', `\appendix', `\entry', or `\index', is a tag. Other commands can make tags as well, if you specify them in the environment variable `TEXTAGS' before invoking `etags'. The value of this environment variable should be a colon-separated list of command names. For example, TEXTAGS="def:newcommand:newenvironment" export TEXTAGS specifies (using Bourne shell syntax) that the commands `\def', `\newcommand' and `\newenvironment' also define tags. * In Lisp code, any function defined with `defun', any variable defined with `defvar' or `defconst', and in general the first argument of any expression that starts with `(def' in column zero, is a tag. * In Scheme code, tags include anything defined with `def' or with a construct whose name starts with `def'. They also include variables set with `set!' at top level in the file. Several other languages are also supported: * In Ada code, functions, procedures, packages, tasks, and types are tags. Use the `--packages-only' option to create tags for packages only. * In assembler code, labels appearing at the beginning of a line, followed by a colon, are tags. * In Bison or Yacc input files, each rule defines as a tag the nonterminal it constructs. The portions of the file that contain C code are parsed as C code. * In Cobol code, tags are paragraph names; that is, any word starting in column 8 and followed by a period. * In Erlang code, the tags are the functions, records, and macros defined in the file. * In Fortran code, functions, subroutines and blockdata are tags. * In Objective C code, tags include Objective C definitions for classes, class categories, methods, and protocols. * In Pascal code, the tags are the functions and procedures defined in the file. * In Perl code, the tags are the procedures defined by the `sub', `my' and `local' keywords. Use `--globals' if you want to tag global variables. * In Postscript code, the tags are the functions. * In Prolog code, a tag name appears at the left margin. * In Python code, `def' or `class' at the beginning of a line generate a tag. You can also generate tags based on regexp matching (*note Etags Regexps::) to handle other formats and languages. File: xemacs.info, Node: Create Tags Table, Next: Etags Regexps, Prev: Tag Syntax, Up: Tags Creating Tags Tables -------------------- The `etags' program is used to create a tags table file. It knows the syntax of several languages, as described in *Note Tag Syntax::. Here is how to run `etags': etags INPUTFILES... The `etags' program reads the specified files, and writes a tags table named `TAGS' in the current working directory. You can intermix compressed and plain text source file names. `etags' knows about the most common compression formats, and does the right thing. So you can compress all your source files and have `etags' look for compressed versions of its file name arguments, if it does not find uncompressed versions. Under MS-DOS, `etags' also looks for file names like `mycode.cgz' if it is given `mycode.c' on the command line and `mycode.c' does not exist. `etags' recognizes the language used in an input file based on its file name and contents. You can specify the language with the `--language=NAME' option, described below. If the tags table data become outdated due to changes in the files described in the table, the way to update the tags table is the same way it was made in the first place. It is not necessary to do this often. If the tags table fails to record a tag, or records it for the wrong file, then Emacs cannot possibly find its definition. However, if the position recorded in the tags table becomes a little bit wrong (due to some editing in the file that the tag definition is in), the only consequence is a slight delay in finding the tag. Even if the stored position is very wrong, Emacs will still find the tag, but it must search the entire file for it. So you should update a tags table when you define new tags that you want to have listed, or when you move tag definitions from one file to another, or when changes become substantial. Normally there is no need to update the tags table after each edit, or even every day. One tags table can effectively include another. Specify the included tags file name with the `--include=FILE' option when creating the file that is to include it. The latter file then acts as if it contained all the files specified in the included file, as well as the files it directly contains. If you specify the source files with relative file names when you run `etags', the tags file will contain file names relative to the directory where the tags file was initially written. This way, you can move an entire directory tree containing both the tags file and the source files, and the tags file will still refer correctly to the source files. If you specify absolute file names as arguments to `etags', then the tags file will contain absolute file names. This way, the tags file will still refer to the same files even if you move it, as long as the source files remain in the same place. Absolute file names start with `/', or with `DEVICE:/' on MS-DOS and MS-Windows. When you want to make a tags table from a great number of files, you may have problems listing them on the command line, because some systems have a limit on its length. The simplest way to circumvent this limit is to tell `etags' to read the file names from its standard input, by typing a dash in place of the file names, like this: find . -name "*.[chCH]" -print | etags - Use the option `--language=NAME' to specify the language explicitly. You can intermix these options with file names; each one applies to the file names that follow it. Specify `--language=auto' to tell `etags' to resume guessing the language from the file names and file contents. Specify `--language=none' to turn off language-specific processing entirely; then `etags' recognizes tags by regexp matching alone (*note Etags Regexps::). `etags --help' prints the list of the languages `etags' knows, and the file name rules for guessing the language. It also prints a list of all the available `etags' options, together with a short explanation. File: xemacs.info, Node: Etags Regexps, Next: Select Tags Table, Prev: Create Tags Table, Up: Tags Etags Regexps ------------- The `--regex' option provides a general way of recognizing tags based on regexp matching. You can freely intermix it with file names. Each `--regex' option adds to the preceding ones, and applies only to the following files. The syntax is: --regex=/TAGREGEXP[/NAMEREGEXP]/ where TAGREGEXP is used to match the lines to tag. It is always anchored, that is, it behaves as if preceded by `^'. If you want to account for indentation, just match any initial number of blanks by beginning your regular expression with `[ \t]*'. In the regular expressions, `\' quotes the next character, and `\t' stands for the tab character. Note that `etags' does not handle the other C escape sequences for special characters. The syntax of regular expressions in `etags' is the same as in Emacs, augmented with the "interval operator", which works as in `grep' and `ed'. The syntax of an interval operator is `\{M,N\}', and its meaning is to match the preceding expression at least M times and up to N times. You should not match more characters with TAGREGEXP than that needed to recognize what you want to tag. If the match is such that more characters than needed are unavoidably matched by TAGREGEXP (as will usually be the case), you should add a NAMEREGEXP, to pick out just the tag. This will enable Emacs to find tags more accurately and to do completion on tag names more reliably. You can find some examples below. The option `--ignore-case-regex' (or `-c') is like `--regex', except that the regular expression provided will be matched without regard to case, which is appropriate for various programming languages. The `-R' option deletes all the regexps defined with `--regex' options. It applies to the file names following it, as you can see from the following example: etags --regex=/REG1/ voo.doo --regex=/REG2/ \ bar.ber -R --lang=lisp los.er Here `etags' chooses the parsing language for `voo.doo' and `bar.ber' according to their contents. `etags' also uses REG1 to recognize additional tags in `voo.doo', and both REG1 and REG2 to recognize additional tags in `bar.ber'. `etags' uses the Lisp tags rules, and no regexp matching, to recognize tags in `los.er'. A regular expression can be bound to a given language, by prepending it with `{lang}'. When you do this, `etags' will use the regular expression only for files of that language. `etags --help' prints the list of languages recognised by `etags'. The following example tags the `DEFVAR' macros in the Emacs source files. `etags' applies this regular expression to C files only: --regex='{c}/[ \t]*DEFVAR_[A-Z_ \t(]+"$[^"]+$"/' This feature is particularly useful when storing a list of regular expressions in a file. The following option syntax instructs `etags' to read two files of regular expressions. The regular expressions contained in the second file are matched without regard to case. --regex=@first-file --ignore-case-regex=@second-file A regex file contains one regular expressions per line. Empty lines, and lines beginning with space or tab are ignored. When the first character in a line is `@', `etags' assumes that the rest of the line is the name of a file of regular expressions. This means that such files can be nested. All the other lines are taken to be regular expressions. For example, one can create a file called `emacs.tags' with the following contents (the first line in the file is a comment): -- This is for GNU Emacs source files {c}/[ \t]*DEFVAR_[A-Z_ \t(]+"$[^"]+$"/\1/ and then use it like this: etags --regex=@emacs.tags *.[ch] */*.[ch] Here are some more examples. The regexps are quoted to protect them from shell interpretation. * Tag Octave files: etags --language=none \ --regex='/[ \t]*function.*=[ \t]*$[^ \t]*$[ \t]*(/\1/' \ --regex='/###key $.*$/\1/' \ --regex='/[ \t]*global[ \t].*/' \ *.m Note that tags are not generated for scripts so that you have to add a line by yourself of the form `###key ' if you want to jump to it. * Tag Tcl files: etags --language=none --regex='/proc[ \t]+$[^ \t]+$/\1/' *.tcl * Tag VHDL files: --language=none \ --regex='/[ \t]*$ARCHITECTURE\|CONFIGURATION$ +[^ ]* +OF/' \ --regex='/[ \t]*$ATTRIBUTE\|ENTITY\|FUNCTION\|PACKAGE\ \( BODY$?\|PROCEDURE\|PROCESS\|TYPE\)[ \t]+$[^ \t(]+$/\3/' File: xemacs.info, Node: Select Tags Table, Next: Find Tag, Prev: Etags Regexps, Up: Tags Selecting a Tags Table ---------------------- At any time Emacs has one "selected" tags table, and all the commands for working with tags tables use the selected one. To select a tags table, use the variable `tag-table-alist'. The value of `tag-table-alist' is a list that determines which `TAGS' files should be active for a given buffer. This is not really an association list, in that all elements are checked. The car of each element of this list is a pattern against which the buffers file name is compared; if it matches, then the cdr of the list should be the name of the tags table to use. If more than one element of this list matches the buffers file name, all of the associated tags tables are used. Earlier ones are searched first. If the car of elements of this list are strings, they are treated as regular-expressions against which the file is compared (like the `auto-mode-alist'). If they are not strings, they are evaluated. If they evaluate to non-`nil', the current buffer is considered to match. If the cdr of the elements of this list are strings, they are assumed to name a tags file. If they name a directory, the string `tags' is appended to them to get the file name. If they are not strings, they are evaluated and must return an appropriate string. For example: (setq tag-table-alist '(("/usr/src/public/perl/" . "/usr/src/public/perl/perl-3.0/") ("\\.el$" . "/usr/local/emacs/src/") ("/jbw/gnu/" . "/usr15/degree/stud/jbw/gnu/") ("" . "/usr/local/emacs/src/") )) The example defines the tags table alist in the following way: * Anything in the directory `/usr/src/public/perl/' should use the `TAGS' file `/usr/src/public/perl/perl-3.0/TAGS'. * Files ending in `.el' should use the `TAGS' file `/usr/local/emacs/src/TAGS'. * Anything in or below the directory `/jbw/gnu/' should use the `TAGS' file `/usr15/degree/stud/jbw/gnu/TAGS'. If you had a file called `/usr/jbw/foo.el', it would use both `TAGS' files, `/usr/local/emacs/src/TAGS' and `/usr15/degree/stud/jbw/gnu/TAGS' (in that order), because it matches both patterns. If the buffer-local variable `buffer-tag-table' is set, it names a tags table that is searched before all others when `find-tag' is executed from this buffer. If there is a file called `TAGS' in the same directory as the file in question, then that tags file will always be used as well (after the `buffer-tag-table' but before the tables specified by this list). If the variable `tags-file-name' is set, the `TAGS' file it names will apply to all buffers (for backwards compatibility.) It is searched first. If the value of the variable `tags-always-build-completion-table' is `t', the tags file will always be added to the completion table without asking first, regardless of the size of the tags file. The function `M-x visit-tags-table', is largely made obsolete by the variable `tag-table-alist', tells tags commands to use the tags table file FILE first. The FILE should be the name of a file created with the `etags' program. A directory name is also acceptable; it means the file `TAGS' in that directory. The function only stores the file name you provide in the variable `tags-file-name'. Emacs does not actually read in the tags table contents until you try to use them. You can set the variable explicitly instead of using `visit-tags-table'. The value of the variable `tags-file-name' is the name of the tags table used by all buffers. This is for backward compatibility, and is largely supplanted by the variable `tag-table-alist'. File: xemacs.info, Node: Find Tag, Next: Tags Search, Prev: Select Tags Table, Up: Tags Finding a Tag ------------- The most important thing that a tags table enables you to do is to find the definition of a specific tag. `M-. TAG &OPTIONAL OTHER-WINDOW' Find first definition of TAG (`find-tag'). `C-u M-.' Find next alternate definition of last tag specified. `C-x 4 . TAG' Find first definition of TAG, but display it in another window (`find-tag-other-window'). `M-.' (`find-tag') is the command to find the definition of a specified tag. It searches through the tags table for that tag, as a string, then uses the tags table information to determine the file in which the definition is used and the approximate character position of the definition in the file. Then `find-tag' visits the file, moves point to the approximate character position, and starts searching ever-increasing distances away for the text that should appear at the beginning of the definition. If an empty argument is given (by typing ), the sexp in the buffer before or around point is used as the name of the tag to find. *Note Lists::, for information on sexps. The argument to `find-tag' need not be the whole tag name; it can be a substring of a tag name. However, there can be many tag names containing the substring you specify. Since `find-tag' works by searching the text of the tags table, it finds the first tag in the table that the specified substring appears in. To find other tags that match the substring, give `find-tag' a numeric argument, as in `C-u M-.'. This does not read a tag name, but continues searching the tag table's text for another tag containing the same substring last used. If your keyboard has a real key, `M-0 M-.' is an easier alternative to `C-u M-.'. If the optional second argument OTHER-WINDOW is non-`nil', it uses another window to display the tag. Multiple active tags tables and completion are supported. Variables of note include the following: `tag-table-alist' Controls which tables apply to which buffers. `tags-file-name' Stores a default tags table. `tags-build-completion-table' Controls completion behavior. `buffer-tag-table' Specifies a buffer-local table. `make-tags-files-invisible' Sets whether tags tables should be very hidden. `tag-mark-stack-max' Specifies how many tags-based hops to remember. Like most commands that can switch buffers, `find-tag' has another similar command that displays the new buffer in another window. `C-x 4 .' invokes the function `find-tag-other-window'. (This key sequence ends with a period.) Emacs comes with a tags table file `TAGS' (in the directory containing Lisp libraries) that includes all the Lisp libraries and all the C sources of Emacs. By specifying this file with `visit-tags-table' and then using `M-.' you can quickly look at the source of any Emacs function.