Vi

is a powerful "modal" text-based editor with a long history in the Unix(like) operating system. The original vi has served as a basis for many clones and derivatives over the years, notably vim.

Although not part of the GNU Coreutils, a vi(like) editor is almost universally included in Linux distributions.

busybox vi
If vi or vim is not installed you can check, if busybox's vi is available: