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Source File Tag Syntax

Here is how tag syntax is defined for the most popular languages:

• In C code, any C function or typedef is a tag, and so are definitions of struct, union and enum. #define macro definitions and enum constants are also tags, unless you specify `--no-defines' when making the tags table. Similarly, global variables are tags, unless you specify `--no-globals'. Use of `--no-globals' and `--no-defines' can make the tags table file much smaller.
• In C++ code, in addition to all the tag constructs of C code, member functions are also recognized, and optionally member variables if you use the `--members' option. Tags for variables and functions in classes are named `class::variable' and `class::function'.
• In Java code, tags include all the constructs recognized in C++, plus the extends and implements constructs. Tags for variables and functions in classes are named `class.variable' and `class.function'.
• In LaTeX text, the argument of any of the commands \chapter, \section, \subsection, \subsubsection, \eqno, \label, \ref, \cite, \bibitem, \part, \appendix, \entry, or \index, is a tag. Other commands can make tags as well, if you specify them in the environment variable TEXTAGS before invoking etags. The value of this environment variable should be a colon-separated list of command names. For example,

  TEXTAGS="def:newcommand:newenvironment"
  export TEXTAGS
  

  specifies (using Bourne shell syntax) that the commands `\def', `\newcommand' and `\newenvironment' also define tags.
• In Lisp code, any function defined with defun, any variable defined with defvar or defconst, and in general the first argument of any expression that starts with `(def' in column zero, is a tag.
• In Scheme code, tags include anything defined with def or with a construct whose name starts with `def'. They also include variables set with set! at top level in the file.

Several other languages are also supported:

• In assembler code, labels appearing at the beginning of a line, followed by a colon, are tags.
• In Bison or Yacc input files, each rule defines as a tag the nonterminal it constructs. The portions of the file that contain C code are parsed as C code.
• In Cobol code, tags are paragraph names; that is, any word starting in column 8 and followed by a period.
• In Erlang code, the tags are the functions, records, and macros defined in the file.
• In Fortran code, functions, subroutines and blockdata are tags.
• In Objective C code, tags include Objective C definitions for classes, class categories, methods, and protocols.
• In Pascal code, the tags are the functions and procedures defined in the file.
• In Perl code, the tags are the procedures defined by the sub keyword.
• In Postscript code, the tags are the functions.
• In Prolog code, a tag name appears at the left margin.

You can also generate tags based on regexp matching (see section Creating Tags Tables) to handle other formats and languages.

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