Tags

In UNIX terminology, a tag table is an index that tells how to find the definition of any certain identifiers (`tags') defined in some collection of source files. In effect, it provides a smart, multi-file search that is particularly useful when navigating in non-trivial directories of source files. Typically, you set things up by going into the directory containing the source text to be indexed and issuing the UNIX command

etags options files

where files is a list of all the source files that need to be indexed. This creates a file named `TAGS' containing the tag table. For C programs, the tags are the names of functions defined in the named source files. The -t option causes etags to record typedef declarations as well. The tag table produced is organized in such a way that simple edits to a source file will not invalidate it. The following Emacs commands deal with tag tables.

M-x visit-tags-table

prompts for the name of a tags table file, and uses its contents in future tag-related searches.

M-.

prompts for a tag and then positions the current window in the file containing its first definition and puts the cursor on that definition. You may also give a null response (just RET), in which case the word before or around the point is used as the tag.

C-u M-.

finds the next alternate definition of the last tag specified.

C-x 4 .

is the same as M-., but displays the text containing the tag in the other window instead of the current one.

M-x tags-search

prompts and searches for a regular expression as for C-M-s, but is does a non-incremental search through all the files given in the currently-visited tag table.

M-x tags-query-replace

acts like M-Q, but looks through all the files given in the currently-visited tag table.

M-,

restarts the last tags-search or tags-query-replace from the current location of the point.

M-x tags-apropos

prompts for a regular expression and displays a list of all tags in the currently-visited table that match it.