GNU ed is a line-oriented text editor. It is used to create, display, modify and otherwise manipulate text files, both interactively and via shell scripts.
Ranked in these QuestionsQuestion Ranking
Pro ed is the standard text editor
As the standard text editor,
ed is available on multiple systems.
Pro Consistent UI
ed has a consistent user interface and error reportage.
Con Not a lot of features
While extremely fast and simple, Ed is simply not for programming for a long time because it lacks a lot of important features. It should be used instead for quick edits.
Con Not a persistent UI
You can only view portions of a file through search or regular expression commands. You cannot scan or scroll through a file using the available screen real-estate.
It's not too dissimilar in use to command-line tools (such as grep and sed) for editing a file. In fact, both grep and sed are based on how interaction is performed with Ed.
There's absolutely no need for ed when you have sed and ex.