Ctags

Tag index files are supported by many source code editors, including:

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• Atom
• BBEdit 8+
• CodeLite (via built-in ctagsd language server){{Cite web |url=https://docs.codelite.org/plugins/lsp/ |title=Language Server Protocol |website=CodeLite Documentation |access-date=2022-06-12}}
• Cloud9 IDE (uses it internally but does not expose it)
• CygnusEd{{Cite web|url=http://aminet.net/package/dev/c/ctags|title = Aminet - dev/C/Ctags.lha}}
• Emacs and XEmacs
• EmEditor Professional
• Far Manager (via Ctags Source Navigator plugin)
• Geany
• Gedit (via [https://web.archive.org/web/20080117145432/http://www.micahcarrick.com/11-14-2007/gedit-symbol-browser-plugin.html gedit-symbol-browser-plugin])
• JED
• jEdit (via plugins CodeBrowser, Tags, ClassBrowser, CtagsSideKick, or Jump)
• JOE
• KDevelop
• Kate
• mcedit (Midnight Commander builtin editor)
• NEdit
• Notepad++ (via OpenCTags plug-in)
• QDevelop
• TSE (via macro)
• TextMate (via CodeBrowser-PlugIn)
• UltraEdit
• TextPad
• VEDIT
• vi (and derivatives such as Elvis, Nvi, Vim, vile, etc.)
• Visual Studio Code[https://donjayamanne.github.io/pythonVSCodeDocs/docs/workspaceSymbols/ Workspace Symbols], Python for Visual Studio Code Docs
• Xedit (X11)

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There are a few other implementations of the ctags program:

GNU Emacs comes with two ctags utilities, etags and ctags, which are compiled from the same source code. Etags generates a tag table file for Emacs, while the ctags command is used to create a similar table in a format understood by vi. They have different sets of command line options:

etags does not recognize and ignores options which only make sense for vi style tag files produced by the ctags command.{{man|1|etags.emacs|ManKier}}

Exuberant Ctags, written and maintained by Darren Hiebert until 2009,{{cite web |title=Exuberant Ctags |url=http://ctags.sourceforge.net/ |website=ctags.sourceforge.net}} was initially distributed with Vim, but became a separate project upon the release of Vim 6. It includes support for Emacs and {{code|etags}} compatibility.{{cite web|url=http://vimdoc.sourceforge.net/htmldoc/version6.html#ctags-gone|title=Vim documentation: version6: ctags-gone|access-date=2007-04-28}}{{man|1|etags.ctags|ManKier}}

Exuberant Ctags includes support for over 40 programming languages with the ability to add support for even more using regular expressions.

Universal Ctags is a fork of Exuberant Ctags, with the objective of continuing its development. A few parsers are rewritten to better support the languages.{{cite web|url=https://docs.ctags.io/|title=Universal Ctags Documentation|access-date=2018-08-02}}

{{vanchor|Hasktags}} creates ctags compatible tag files for Haskell source files.{{cite web|url=http://haskell.org/ghc/docs/latest/html/users_guide/utils.html#hasktags|title=GHC documentation: Other Haskell utility programs|access-date=2010-03-05}} It includes support for creating Emacs etags files.{{cite web|url=http://hackage.haskell.org/package/hasktags|title=hasktags: Produces ctags "tags" and etags "TAGS" files for Haskell programs|access-date=2010-03-05}}

{{vanchor|jsctags}} is a ctags-compatible code indexing solution for JavaScript.{{cite web|url=https://github.com/pcwalton/jsctags|title=pcwalton github repository for jsctags|website=GitHub |access-date=2016-09-10|archive-url=https://web.archive.org/web/20100822181929/http://github.com/pcwalton/jsctags|archive-date=2010-08-22|url-status=dead}} It is specialized for JavaScript and uses the CommonJS packaging system. It outperforms Exuberant Ctags for JavaScript code, finding more tags than the latter.{{cite web|url=http://pcwalton.blogspot.com/2010/05/introducing-jsctags.html|title=Introducing jsctags|author=Patrick Walton|date=25 May 2010|access-date=2010-05-25}}

There are multiple tag file formats. Some of them are described below. In the following, {{mono|\x##}} represents the byte with hexadecimal representation {{mono|##}}. Every line ends with a line feed (LF, {{mono|\n}} = {{mono|\x0A}}).

The original ctags and the Exuberant/Universal descendants have similar file formats:{{cite web|url=http://ctags.sourceforge.net/FORMAT|title=Proposal for extended Vi tags file format|access-date=2007-06-30}}

This is the format used by vi and various clones. The tags file is normally named "tags".

The tags file is a list of lines, each line in the format:

{tagname}\t{tagfile}\t{tagaddress}

The fields are specified as follows:

• {{mono|{tagname}}} – Any identifier, not containing white space
• {{mono|\t}} – Exactly one tab ({{mono|\x0b}}) character, although many versions of vi can handle any amount of white space.
• {{mono|{tagfile}}} – The name of the file where {{mono|{tagname}}} is defined, relative to the current directory
• {{mono|{tagaddress}}} – An ex mode command that will take the editor to the location of the tag. For POSIX implementations of vi this may only be a search or a line number, providing added security against arbitrary command execution.

The tags file is sorted on the {{mono|{tagname}}} field which allows for fast searching of the tags file.

This is the format used by Vim's Exuberant Ctags and Universal Ctags. These programs can generate an original ctags file format or an extended format that attempts to retain backward compatibility.

The extended tags file is a list of lines, each line in the format:

{tagname}\t{tagfile}\t{tagaddress}[;"\t{tagfield...}]

The fields up to and including {{mono|{tagaddress}}} are the same as for ctags above.

Optional additional fields are indicated by square brackets ("[...]") and include:

• {{mono|;"}} – semicolon + double quote: Ends the {{mono|{tagaddress}}} in a way that looks like the start of a comment to vi or ex.
• {{mono|{tagfield}}} – extension fields: tab separated "key:value" pairs for more information.

This format is compatible with non-POSIX vi as the additional data is interpreted as a comment. POSIX implementations of vi must be changed to support it, however.

This is the format used by Emacs etags. The tags file is normally named "TAGS".

The etags files consists of multiple sections—one section per input source file. Sections are plain-text with several non-printable ascii characters used for special purposes. These characters are represented as underlined hexadecimal codes below.

A section starts with a two line header (the first two bytes make up a magic number):

\x0c

{src_file},{size_of_tag_definition_data_in_bytes}

The header is followed by tag definitions, one definition per line, with the format:

{tag_definition_text}\x7f{tagname}\x01{line_number},{byte_offset}

{{mono|{tagname}\x01}} can be omitted if the name of the tag can be deduced from the text at the tag definition.

Given a single line test.c source code:

#define CCC(x)

The TAGS (etags) file would look like this:

\x0c

test.c,21

#define CCC(\x7fCCC\x011,0

The tags (ctags) file may look like:

CCC(	test.c	1

or more flexibly using a search:

CCC(	test.c	/^#define CCC(/

• GNU GLOBAL

{{Reflist}}

{{Wikibooks|Guide to Unix|Commands}}

• {{man|cu|ctags|SUS|create a tags file}}
• [https://ctags.io Universal Ctags homepage]
• [http://ctags.sourceforge.net Exuberant Ctags homepage]
• [http://polarhome.com/ctags/?lang=en Ctags on VMS]
• [http://cvs.savannah.gnu.org/viewvc/vtags/vtags/vtags.el?view=markup source code for Emacs vtags.el module]

{{Unix commands}}

Category:Code comprehension tools

Category:Code navigation tools

Category:Free computer programming tools

Category:Unix programming tools

Category:Standard Unix programs

Category:Unix SUS2008 utilities

Category:Software using the BSD license

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