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(emacs)Etags Regexps

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Etags Regexps
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   The `--regex' option provides a general way of recognizing tags
based on regexp matching.  You can freely intermix it with file names.
Each `--regex' option adds to the preceding ones, and applies only to
the following files.  The syntax is:

     --regex=/TAGREGEXP[/NAMEREGEXP]/

where TAGREGEXP is used to match the lines to tag.  It is always
anchored, that is, it behaves as if preceded by `^'.  If you want to
account for indentation, just match any initial number of blanks by
beginning your regular expression with `[ \t]*'.  In the regular
expressions, `\' quotes the next character, and `\t' stands for the tab
character.  Note that `etags' does not handle the other C escape
sequences for special characters.

   The syntax of regular expressions in `etags' is the same as in
Emacs, augmented with the "interval operator", which works as in `grep'
and `ed'.  The syntax of an interval operator is `\{M,N\}', and its
meaning is to match the preceding expression at least M times and up to
N times.

   You should not match more characters with TAGREGEXP than that needed
to recognize what you want to tag.  If the match is such that more
characters than needed are unavoidably matched by TAGREGEXP (as will
usually be the case), you should add a NAMEREGEXP, to pick out just the
tag.  This will enable Emacs to find tags more accurately and to do
completion on tag names more reliably.  You can find some examples
below.

   The option `--ignore-case-regex' (or `-c') works like `--regex',
except that matching ignores case.  This is appropriate for certain
programming languages.

   The `-R' option deletes all the regexps defined with `--regex'
options.  It applies to the file names following it, as you can see
from the following example:

     etags --regex=/REG1/ voo.doo --regex=/REG2/ \
         bar.ber -R --lang=lisp los.er

Here `etags' chooses the parsing language for `voo.doo' and `bar.ber'
according to their contents.  `etags' also uses REG1 to recognize
additional tags in `voo.doo', and both REG1 and REG2 to recognize
additional tags in `bar.ber'.  `etags' uses the Lisp tags rules, and no
regexp matching, to recognize tags in `los.er'.

   You can specify a regular expression for a particular language, by
writing `{lang}' in front of it.  Then `etags' will use the regular
expression only for files of that language.  (`etags --help' prints the
list of languages recognized by `etags'.)  The following example tags
the `DEFVAR' macros in the Emacs source files, for the C language only:

     --regex='{c}/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/'

This feature is particularly useful when you store a list of regular
expressions in a file.  The following option syntax instructs `etags'
to read two files of regular expressions.  The regular expressions
contained in the second file are matched without regard to case.

     --regex=@first-file --ignore-case-regex=@second-file

A regex file contains one regular expressions per line.  Empty lines,
and lines beginning with space or tab are ignored.  When the first
character in a line is `@', `etags' assumes that the rest of the line
is the name of a file of regular expressions; thus, one such file can
include another file.  All the other lines are taken to be regular
expressions.  If the first non-whitespace text on the line is `--',
that line is a comment.

   For example, one can create a file called `emacs.tags' with the
following contents:

             -- This is for GNU Emacs C source files
     {c}/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/\1/

and then use it like this:

     etags --regex=@emacs.tags *.[ch] */*.[ch]

   Here are some more examples.  The regexps are quoted to protect them
from shell interpretation.

   * Tag Octave files:

          etags --language=none \
                --regex='/[ \t]*function.*=[ \t]*\([^ \t]*\)[ \t]*(/\1/' \
                --regex='/###key \(.*\)/\1/' \
                --regex='/[ \t]*global[ \t].*/' \
                *.m

     Note that tags are not generated for scripts, so that you have to
     add a line by yourself of the form `###key SCRIPTNAME' if you want
     to jump to it.

   * Tag Tcl files:

          etags --language=none --regex='/proc[ \t]+\([^ \t]+\)/\1/' *.tcl

   * Tag VHDL files:

          etags --language=none \
            --regex='/[ \t]*\(ARCHITECTURE\|CONFIGURATION\) +[^ ]* +OF/' \
            --regex='/[ \t]*\(ATTRIBUTE\|ENTITY\|FUNCTION\|PACKAGE\
            \( BODY\)?\|PROCEDURE\|PROCESS\|TYPE\)[ \t]+\([^ \t(]+\)/\3/'