How to output lines with ex command that is vi not vim?

Question

I am using ArchLinux and I want to run some ex commands. The following outputs nothing on my system:

$ ex -s -c %p -c q /etc/hosts

The ex command is a part of vi package on my system:

$ pacman -Ql vi
vi /usr/bin/ex
vi /usr/bin/vi
...
$ pacman -Q vi
vi 1:070224-6
$ ex --help
ex: illegal option -- -
Usage: ex [- | -s] [-l] [-L] [-R] [-r [file]] [-t tag]
       [-v] [-V] [-w size] [+cmd | -c cmd] file...

In comparison, on my friends PC, ex is a symlink to vim:

$ ex --help | head
VIM - Vi IMproved 8.0 (2016 Sep 12)

usage: vim [arguments] [file ..]       edit specified file(s)
   or: vim [arguments] -               read text from stdin
   or: vim [arguments] -t tag          edit file where tag is defined
   or: vim [arguments] -q [errorfile]  edit file with first error

Arguments:
   --                   Only file names after this
   -v                   Vi mode (like "vi")
$ ex -s -c %p -c q /etc/hosts | wc
     29      92     935

How to output the buffer using ex from vi package, not using ex from vim? What is the difference? Why does ex from vi does not work as expected?

---

What kind of modification are you trying to do?

I am generating tags file for m4 file. Consider the following gentags.sh script:

#!/bin/bash
set -euo pipefail

has() { hash "$@" 2>/dev/null; }
fatal() { echo "$(basename "$0"): $*" >&2; exit 123; }


if (($#)); then
        method=$1
elif has nvim; then
        method=nvim
elif has ex; then
        method=ex
elif has vi; then
        method=vi
elif has vim; then
        method=vim
else
        fatal "no method, choose ex, vi, vim or nvim"
fi

case "$method" in
        ex) vi=(ex -s) ;;
        vi) vi=(vi -s) ;;
        vim) vi=(vim -EsR) ;;
        nvim) vi=(nvim -EsR) ;;
        *) fatal "Internal error" ;;
esac

export LC_ALL=C
rgx='\m^\s*m4_define\w*(\_s*«'
cmd=(
        "${vi[@]}"
        -c         'g!/'"$rgx"'\(\w*\)\>.*/d'
        -c '%s//\1\t\t\/'"${rgx//'\'/'\\'}"'\\zs\1\\>\/;"/'
        -c '%s/\t\zs\ze\t/\=expand("%")/'
        -c '%sort u'
        -c "w ./tags"
        -c 'q!'
        ./test.m4
)
set -x
rm -fv ./tags
"${cmd[@]}"
wc ./tags
head ./tags

Given test.m4 with the following content:

m4_define(«a», «b»)

Running ./gentags.sh nvim results in ./tags file with the following content:

a       ./test.m4       /\m^\s*m4_define\w*(\_s*«\zsa\>/;"

However, running ./gentags ex or vi or vim does not work, neither with -c "w ./tags" or with -c %p and redirection.

Would sed serve your purposes?

No, sed does not really have good support for multiline regexes. \_s* is perfecr for me use-case, and the same vi regex can be re-used inside tags file.