Ctags

ctags recurses through your source tree, and records classes, methods etc.
Currently, the most active derivative of ctags is universal-ctags .

Documentation

universal-ctags home	https://ctags.io/
universal-ctags github	https://github.com/universal-ctags/ctags

History

                   ctags (bsd 3.0  - ships w/ base-system in FreeBSD)
                         |
                         |
                         |
           +-------------+----------+
           |                        |
           |                        |
  exuberant-ctags (e-ctags)      gnu-ctags
           |
           |
  universal-ctags (u-ctags)

Install

# Archlinux
pacman -S ctags  # (upstream: universal-ctags -- see https://archlinux.org/packages/extra/x86_64/ctags/ )

# nixos
nix-env -i universal-ctags

# FreeBSD
pkg install ctags            # (upstream: exuberant-ctags -- see https://svnweb.freebsd.org/ports/head/devel/ctags/pkg-descr?revision=426827&view=markup )
pkg install universal-ctags  # (upstream: universal-ctags )

Usage

ctags --list-languages  # list builtin languages
ctags -R .              # generate tags