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
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, 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 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 derived 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 intermixed 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 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 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; 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 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 supported: \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\( BODY\)?\
\|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 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 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.

-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, 2001-2022 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 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 translation approved by the Free Software Foundation.


GNU Tools 2022-06-10 ETAGS(1)