name file context
where name is the function or macro name, file is the source file in which name is defined, and context is a search pattern that shows the line of code containing name. After the list of tags is created, you can invoke vi on any file and type:
:set tags=tagsfile :tag name
This switches the vi editor to the source file associated with the name listed in tagsfile (which you specify with -t).
etags produces an equivalent file for tags to be used with Emacs