etags program is used to create a tags table file. It knows
the syntax of several languages, as described in
Here is how to run
etags program reads the specified files, and writes a tags
table named TAGS in the current working directory. You can
optionally specify a different file name for the tags table by using the
‘--output=file’ option; specifying - as a file name
prints the tags table to standard output.
If the specified files don’t exist,
etags looks for
compressed versions of them and uncompresses them to read them. Under
etags also looks for file names like mycode.cgz
if it is given ‘mycode.c’ on the command line and mycode.c
does not exist.
If the tags table becomes outdated due to changes in the files
described in it, you can update it by running the
program again. If the tags table does not record a tag, or records it
for the wrong file, then Emacs will not be able to find that
definition until you update the tags table. But if the position
recorded in the tags table becomes a little bit wrong (due to other
editing), Emacs will still be able to find the right position, with a
Thus, there is no need to update the tags table after each edit. You should update a tags table when you define new tags that you want to have listed, or when you move tag definitions from one file to another, or when changes become substantial.
You can make a tags table include another tags table, by
passing the ‘--include=file’ option to
then covers all the files covered by the included tags file, as well
as its own.
If you specify the source files with relative file names when you run
etags, the tags file will contain file names relative to the
directory where the tags file was initially written. This way, you can
move an entire directory tree containing both the tags file and the
source files, and the tags file will still refer correctly to the source
files. If the tags file is - or is in the /dev directory,
however, the file names are
made relative to the current working directory. This is useful, for
example, when writing the tags to the standard output.
When using a relative file name, it should not be a symbolic link pointing to a tags file in a different directory, because this would generally render the file names invalid.
If you specify absolute file names as arguments to
the tags file will contain absolute file names. This way, the tags file
will still refer to the same files even if you move it, as long as the
source files remain in the same place. Absolute file names start with
‘/’, or with ‘device:/’ on MS-DOS and MS-Windows.
When you want to make a tags table from a great number of files,
you may have problems listing them on the command line, because some
systems have a limit on its length. You can circumvent this limit by
etags to read the file names from its standard
input, by typing a dash in place of the file names, like this:
find . -name '*.[chCH]' -print | etags -
etags recognizes the language used in an input file based
on its file name and contents. You can specify the language
explicitly with the ‘--language=name’ option. You can
intermix these options with file names; each one applies to the file
names that follow it. Specify ‘--language=auto’ to tell
etags to resume guessing the language from the file names
and file contents. Specify ‘--language=none’ to turn off
language-specific processing entirely; then
tags by regexp matching alone (see Etags Regexps).
The option ‘--parse-stdin=file’ is mostly useful when
etags from programs. It can 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
‘etags --help’ outputs the list of the languages
knows, and the file name rules for guessing the language. It also prints
a list of all the available
etags options, together with a short
explanation. If followed by one or more ‘--language=lang’
options, it outputs detailed information about how tags are generated for