ed

The original Unix text editor. See also: awk, sed. More information: https://www.gnu.org/software/ed/manual/ed_manual.html.

Start an interactive editor session with an empty document:

ed

Start an interactive editor session with an empty document and a specific [p]rompt:

ed -p '> '

Start an interactive editor session with an empty document and without diagnostics, byte counts and '!' prompt:

ed -s

Edit a specific file (this shows the byte count of the loaded file):

ed {{path/to/file}}

Replace a string with a specific replacement for all lines:

,s/{{regular_expression}}/{{replacement}}/g