ETAGS(1) GNU ETAGS(1)
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 un-
derstood by emacs(1); the ctags program is used to create a similar ta-
ble 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, Er-
lang, 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 directory 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 using 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 de-
fault 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 declara-
tions, 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 defini-
tions 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 derived languages.
--no-globals
Do not tag global variables in C and derived languages. Typi-
cally 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 col-
umn 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 col-
umn zero.
-l language, --language=language
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 de-
fault filename extensions. For example, as Mercury and Objec-
tive-C have same filename extension .m, a test based on contents
tries to detect the language. If this test fails, --lan-
guage=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 dis-
able language parsing altogether; 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 standard 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
Java. For Objective C, this also produces class methods quali-
fied 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; overrides 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 op-
tion 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 use-
ful 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 supported: \a, \b, \d, \e, \f, \n, \r, \t, \v, which respec-
tively 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 char-
acter is needed inside the regular expression, it must be quoted
by preceding it with \.
The optional {language} prefix means that the tag should be cre-
ated 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 con-
tains 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]*\(ARCHITECTURE\|\ CONFIGURA-
TION\) +[^ ]* +OF/' --regex='/[ \t]*\ \(ATTRIBUTE\|ENTITY\|FUNC-
TION\|PACKAGE\( BODY\)?\ \|PROCE-
DURE\|PROCESS\|TYPE\)[ \t]+\([^ \t(]+\)/\3/'
Tag TCL files (this last example shows the usage of a tagreg-
exp):
--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 par-
ticularly 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 imple-
mented 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 op-
tion.
-h, -H, --help
Print usage information. Followed by one or more --lan-
guage=LANG prints detailed information about how tags are creat-
ed 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, 2001-2022 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this
document provided the copyright notice 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 per-
mission notice identical to this one.
Permission is granted to copy and distribute translations of this docu-
ment 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)
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