Make Emacs Line-Oriented

Question

I heard that Vim has an ex mode which is line-oriented.
That means users can use the editor by echoing commands to it, e.g.,

bash$ echo "123" > 123.txt  # 123.txt: 123
bash$ echo "s/2/0
> w" | vim -e 123.txt       # replace "2" with "0", then save the edit
bash$ cat 123.txt           # 123.txt: 103
103

---

Is it possible for Emacs to do this?
If yes, how?

Or, more generally,
has Emacs implemented the line-oriented feature?
If not, why?

Answer 1

emacs -batch can do that:

echo '(progn (find-file "123.txt") (replace-string "2" "0") (save-buffer))' | emacs -batch --eval "(call-interactively #'eval-expression)"

This starts emacs in batch mode where it evaluates its command-line arguments and exits. In this case, the only command line argument is --eval which is asked to call eval-expression interactively. Normally eval-expression reads from the minibuffer, but in batch mode there is no minibuffer and eval-expression reads from stdin. The pipe has arranged for Emacs's stdin to be connected with the stdout of echo, so eval-expression ends up being called with the echo output as its argument. It proceeds to open the file, replace the string and save the buffer. Emacs then exits.

Equivalently but a bit closer in spirit to your example:

echo '(progn (replace-string "2" "0") (save-buffer))' | emacs -batch --file 123.txt --eval "(call-interactively #'eval-expression)"

Here Emacs gets two arguments, a --file argument that visits the file and an --eval argument as before.

Answer 2

According to @NickD’s answer,
to make Emacs line-oriented just like Vim’s ex mode, use:

$ emacs -batch \
>       -eval "(while t \
>                (write-char ?\\n) \
>                (call-interactively #'eval-expression))"

This will provide you with a read and execute loop.