33.3.5 Finding a Tag

The most important thing that a tags table enables you to do is to find the definition of a specific tag.

M-. tag <RET>

Find first definition of tag (find-tag).

C-u M-.

Find next alternate definition of last tag specified.

C-u - M-.

Go back to previous tag found.

C-M-. pattern <RET>

Find a tag whose name matches pattern (find-tag-regexp).

C-u C-M-.

Find the next tag whose name matches the last pattern used.

C-x 4 . tag <RET>

Find first definition of tag, but display it in another window (find-tag-other-window).

C-x 5 . tag <RET>

Find first definition of tag, and create a new frame to select the buffer (find-tag-other-frame).

M-*

Pop back to where you previously invoked M-. and friends.

M-. (find-tag) is the command to find the definition of a specified tag. It searches through the tags table for that tag, as a string, and then uses the tags table info to determine the file that the definition is in and the approximate character position in the file of the definition. Then find-tag visits that file, moves point to the approximate character position, and searches ever-increasing distances away to find the tag definition.

If an empty argument is given (just type <RET>), the balanced expression in the buffer before or around point is used as the tag argument. See section Expressions with Balanced Parentheses.

You don't need to give M-. the full name of the tag; a part will do. This is because M-. finds tags in the table which contain tag as a substring. However, it prefers an exact match to a substring match. To find other tags that match the same substring, give find-tag a numeric argument, as in C-u M-.; this does not read a tag name, but continues searching the tags table's text for another tag containing the same substring last used. If you have a real <META> key, M-0 M-. is an easier alternative to C-u M-..

Like most commands that can switch buffers, find-tag has a variant that displays the new buffer in another window, and one that makes a new frame for it. The former is C-x 4 ., which invokes the command find-tag-other-window. The latter is C-x 5 ., which invokes find-tag-other-frame.

To move back to places you've found tags recently, use C-u - M-.; more generally, M-. with a negative numeric argument. This command can take you to another buffer. C-x 4 . with a negative argument finds the previous tag location in another window.

As well as going back to places you've found tags recently, you can go back to places from where you found them. Use M-*, which invokes the command pop-tag-mark, for this. Typically you would find and study the definition of something with M-. and then return to where you were with M-*.

Both C-u - M-. and M-* allow you to retrace your steps to a depth determined by the variable find-tag-marker-ring-length.

The command C-M-. (find-tag-regexp) visits the tags that match a specified regular expression. It is just like M-. except that it does regexp matching instead of substring matching.