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etags(1) GNU Tools etags(1)


etags, ctags - generate tag file for Emacs, vi


etags [-aCDGImRVh] [-i file] [-l language]
[-o tagfile] [-r regexp]
[--append] [--no-defines] [--no-globals] [--include=file] [--ignore-indentation] [--language=language] [--members] [--output=tagfile] [--regex=regexp] [--no-regex] [--ignore-case-regex=regexp] [--help] [--version] file ...

ctags [-aCdgImRVh] [-BtTuvwx] [-l language]
[-o tagfile] [-r regexp]
[--append] [--backward-search] [--cxref] [--defines] [--forward-search] [--globals] [--ignore-indentation] [--language=language] [--members] [--output=tagfile] [--regex=regexp] [--ignore-case-regex=regexp] [--typedefs] [--typedefs-and-c++] [--update] [--no-warn] [--help] [--version] file ...


The `etags' program is used to create a tag table file, in a format understood by emacs(1); the `ctags' program is used to create a similar table in a format understood by vi(1). Both forms of the program understand the syntax of C, Objective C, C++, Java, Fortran, Ada, Cobol, Erlang, LaTeX, Emacs Lisp/Common Lisp, makefiles, Pascal, Perl, Postscript, Python, Prolog, Scheme and most assembler-like syntaxes. Both forms read the files specified on the command line, and write a tag table (defaults: `TAGS' for etags, `tags' for ctags) in the current working directory. Files specified with relative file names will be recorded in the tag table with file names relative to the directory where the tag table resides. Files specified with absolute file names will be recorded with absolute file names. The programs recognize the language used in an input file based on its file name and contents. The --language switch can be used to force parsing of the file names following the switch according to the given language, overriding guesses based on filename extensions.


Some options make sense only for the vi style tag files produced by ctags; etags does not recognize them. The programs accept unambiguous abbreviations for long option names.

Append to existing tag file. (For vi-format tag files, see also --update.)
Tag files written in the format expected by vi contain regular expression search instructions; the -B option writes them using the delimiter `?', to search backwards through files. The default is to use the delimiter `/', to search forwards through files. Only ctags accepts this option.
In C and derived languages, create tags for function declarations, and create tags for extern variables unless --no-globals is used.
Create tag entries for C preprocessor constant definitions and enum constants, too. This is the default behavior for etags.
Do not create tag entries for C preprocessor constant definitions and enum constants. This may make the tags file much smaller if many header files are tagged. This is the default behavior for ctags.
Create tag entries for global variables in C, C++, Objective C, Java, and Perl. This is the default behavior for etags.
Do not tag global variables. Typically this reduces the file size by one fourth. This is the default behavior for ctags.
Include a note in the tag file indicating that, when searching for a tag, one should also consult the tags file file after checking the current file. This options is only accepted by etags.
Don't rely on indentation as much as we normally do. Currently, this means not to assume that a closing brace in the first column is the final brace of a function or structure definition in C and C++.
Parse the following files according to the given language. More than one such options may be intermixed with filenames. Use --help to get a list of the available languages and their default filename extensions. The `auto' language can be used to restore automatic detection of language based on the file name. The `none' language may be used to disable language parsing altogether; only regexp matching is done in this case (see the --regex option).
Create tag entries for variables that are members of structure-like constructs in C++, Objective C, Java.
Do not tag member variables. This is the default behavior.
Only tag packages in Ada files.
Explicit name of file for tag table; overrides default `TAGS' or `tags'. (But ignored with -v or -x.)
Make tags based on regexp matching for each line of the files following this option, in addition to the tags made with the standard parsing based on language. When using --regex, case is significant, while it is not with --ignore-case-regex. May be freely intermixed with filenames and the -R option. The regexps are cumulative, i.e. each option will add to the previous ones. The regexps are of the form:

where tagregexp is used to match the lines that must be tagged. It should not match useless characters. If the match is such that more characters than needed are unavoidably matched by tagregexp, it may be useful to add a nameregexp, to narrow down the tag scope. ctags ignores regexps without a nameregexp. The syntax of regexps is the same as in emacs, augmented with intervals of the form \{m,n\}, as in ed or grep.
Here are some examples. All the regexps are quoted to protect them from shell interpretation.

Tag the DEFVAR macros in the emacs source files:
--regex='/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"'

Tag VHDL files (this example is a single long line, broken here for formatting reasons):
--language=none --regex='/[ \t]*\(ARCHITECTURE\|\ CONFIGURATION\) +[^ ]* +OF/' --regex='/[ \t]*\ \(ATTRIBUTE\|ENTITY\|FUNCTION\|PACKAGE\( BODY\)?\ \|PROCEDURE\|PROCESS\|TYPE\)[ \t]+\([^ \t(]+\)/\3/'

Tag TCL files (this last example shows the usage of a tagregexp):
--lang=none --regex='/proc[ \t]+\([^ \t]+\)/\1/'

A regexp can be preceded by {lang}, thus restriciting it to match lines of files of the specified language. Use etags --help to obtain a list of the recognised languages. This feature is particularly useful inside regex files. A regex file contains one regex per line. Empty lines, and those lines beginning with space or tab are ignored. Lines beginning with @ are references to regex files whose name follows the @ sign. Other lines are considered regular expressions like those following --regex.
For example, the command
etags --regex=@regex.file *.c
reads the regexes contained in the file regex.file.

Don't do any more regexp matching on the following files. May be freely intermixed with filenames and the --regex option.
Record typedefs in C code as tags. Since this is the default behaviour of etags, only ctags accepts this option.
Generate tag entries for typedefs, struct, enum, and union tags, and C++ member functions. Since this is the default behaviour of etags, only ctags accepts this option.
Update tag entries for files specified on command line, leaving tag entries for other files in place. Currently, this is implemented by deleting the existing entries for the given files and then rewriting the new entries at the end of the tags file. It is often faster to simply rebuild the entire tag file than to use this. Only ctags accepts this option.
Instead of generating a tag file, write index (in vgrind format) to standard output. Only ctags accepts this option.
Suppress warning messages about duplicate entries. The etags program does not check for duplicate entries, so this option is not allowed with it.
Instead of generating a tag file, write a cross reference (in cxref format) to standard output. Only ctags accepts this option.
Print usage information.
Print the current version of the program (same as the version of the emacs etags is shipped with).


`emacs' entry in info; GNU Emacs Manual, Richard Stallman.
cxref(1), emacs(1), vgrind(1), vi(1).


Copyright (c) 1999 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be included in translations approved by the Free Software Foundation instead of in the original English.

14gen2001 GNU Tools