Provided by: emacs-common_29.3+1-1ubuntu2_all 
NAME
etags, ctags - generate tag file for Emacs, vi
SYNOPSIS
etags [-aCDGIQRVh] [-i file] [-l language]
[-o tagfile] [-r regexp] [--parse-stdin=file]
[--append] [--no-defines] [--globals] [--no-globals] [--no-line-directive] [--include=file]
[--ignore-indentation] [--language=language] [--members] [--no-members] [--output=tagfile]
[--class-qualify] [--regex=regexp] [--no-regex] [--help] [--version] file ...
ctags [-aCdgIQRVh] [-BtTuvwx] [-l language]
[-o tagfile] [-r regexp] [--parse-stdin=file]
[--append] [--backward-search] [--cxref] [--no-defines] [--globals] [--no-globals] [--no-line-directive]
[--ignore-indentation] [--language=language] [--members] [--no-members] [--class-qualify]
[--output=tagfile] [--regex=regexp] [--update] [--help] [--version] file ...
DESCRIPTION
The etags program is used to create a tag table file, in a format understood by emacs(1); the ctags pro‐
gram is used to create a similar table in a format understood by vi(1). Both forms of the program under‐
stand the syntax of C, Objective C, C++, Java, Fortran, Ada, Cobol, Erlang, Forth, Go, HTML, LaTeX, Emacs
Lisp/Common Lisp, Lua, Makefile, Mercury, Pascal, Perl, Ruby, Rust, PHP, 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 di‐
rectory where the tag table resides. If the tag table is in /dev or is the standard output, however, the
file names are made relative to the working directory. Files specified with absolute file names will be
recorded with absolute file names. Files generated from a source file--like a C file generated from a
source Cweb file--will be recorded with the name of the source file. Compressed files are supported us‐
ing gzip, bzip2, xz, and zstd. 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.
OPTIONS
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.
-a, --append
Append to existing tag file. (For vi-format tag files, see also --update.)
-B, --backward-search
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.
--declarations
In C and derived languages, create tags for function declarations, and create tags for extern
variables unless --no-globals is used. In Lisp, create tags for (defvar foo) declarations. In
Mercury, declarations start a line with ":-" and are always tagged. In addition, this option tags
predicates or functions in first rules of clauses, as in Prolog.
-D, --no-defines
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.
--globals
Create tag entries for global variables in Perl and Makefile. This is the default in C and de‐
rived languages.
--no-globals
Do not tag global variables in C and derived languages. Typically this reduces the file size by
one fourth.
--no-line-directive
Ignore #line preprocessor directives in C and derived languages. The default is to honor those
directives, and record the tags as if the file scanned was the one named in the #line directive.
This switch is useful when the original file named by #line is no longer available.
-i file, --include=file
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. Only etags accepts this option.
-I, --ignore-indentation
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++. This is important for code that doesn't observe the GNU Coding conventions of placing
only top-level braces in column zero.
-l language, --language=language
Parse the following files according to the given language. More than one such options may be in‐
termixed with filenames. Use --help to get a list of the available languages and their default
filename extensions. For example, as Mercury and Objective-C have same filename extension .m, a
test based on contents tries to detect the language. If this test fails, --language=mercury or
--language=objc should be used. 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 al‐
together; only regexp matching is done in this case (see the --regex option).
--members
Create tag entries for variables that are members of structure-like constructs in PHP. This is
the default for C and derived languages.
--no-members
Do not tag member variables.
--packages-only
Only tag packages in Ada files.
--parse-stdin=file
May be used (only once) in place of a file name on the command line. etags will read from stan‐
dard input and mark the produced tags as belonging to the file FILE.
-Q, --class-qualify
Qualify tag names with their class name in C++, ObjC, Java, and Perl. This produces tag names of
the form class::member for C++ and Perl, class(category) for Objective C, and class.member for Ja‐
va. For Objective C, this also produces class methods qualified with their arguments, as in
foo:bar:baz:more.
-o tagfile, --output=tagfile
Explicit name of file for tag table; for etags only, a file name of - means standard output; over‐
rides default TAGS or tags. (But ignored with -v or -x.)
-r regexp, --regex=regexp
Make tags based on regexp matching for the files following this option, in addition to the tags
made with the standard parsing based on language. May be freely intermixed with filenames and the
-R option. The regexps are cumulative, i.e., each such option will add to the previous ones. The
regexps are of one of the forms:
[{language}]/tagregexp/[nameregexp/]modifiers
@regexfile
where tagregexp is used to match the tag. 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. The following character escape sequences are support‐
ed: \a, \b, \d, \e, \f, \n, \r, \t, \v, which respectively stand for the ASCII characters BEL, BS,
DEL, ESC, FF, NL, CR, TAB, VT.
The modifiers are a sequence of 0 or more characters among i, which means to ignore case when
matching; m, which means that the tagregexp will be matched against the whole file contents at
once, rather than line by line, and the matching sequence can match multiple lines; and s, which
implies m and means that the dot character in tagregexp matches the newline char as well.
The separator, which is / in the examples, can be any character different from space, tab, braces
and @. If the separator character is needed inside the regular expression, it must be quoted by
preceding it with \.
The optional {language} prefix means that the tag should be created only for files of language
language, and ignored otherwise. This is particularly useful when storing many predefined regexps
in a file.
In its second form, regexfile is the name of a file that contains a number of arguments to the
--regex= option, one per line. Lines beginning with a space or tab are assumed to be comments,
and ignored.
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\( BODY\)?\ \|PROCE‐
DURE\|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 restricting it to match lines of files of the specified
language. Use etags --help to obtain a list of the recognized languages. This feature is partic‐
ularly 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.
-R, --no-regex
Don't do any more regexp matching on the following files. May be freely intermixed with filenames
and the --regex option.
-u, --update
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.
-v, --vgrind
Instead of generating a tag file, write index (in vgrind format) to standard output. Only ctags
accepts this option.
-x, --cxref
Instead of generating a tag file, write a cross reference (in cxref format) to standard output.
Only ctags accepts this option.
-h, -H, --help
Print usage information. Followed by one or more --language=LANG prints detailed information
about how tags are created for LANG.
-V, --version
Print the current version of the program (same as the version of the emacs etags is shipped with).
SEE ALSO
"emacs" entry in info; GNU Emacs Manual, Richard Stallman.
cxref(1), emacs(1), vgrind(1), vi(1).
COPYING
Copyright 1992, 1999, 2001-2024 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this document provided the copyright no‐
tice and this permission notice are preserved on all copies.
Permission is granted to copy and distribute modified versions of this document 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 document into another language, under
the above conditions for modified versions, except that this permission notice may be stated in a trans‐
lation approved by the Free Software Foundation.
GNU Tools 2022-06-10 ETAGS(1)