etags - Unix, Linux Command

where tagregexp is used to match the lines that must be tagged. 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, augmented with intervals of the form \{m,n\}, as in ed or grep.
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 recognised 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 [email protected] *.c
reads the regexes contained in the file regex.file.