Need to print stdout and raise(stderr) on error

demo.rb

#!/usr/bin/env ruby
require 'open3'

# CONTEXT
#
# I need to print stdout message and raise(stderr) on error
#
# System used: OpenBSD
# Commands used pkg_delete ; pkg_add
# Output is interactive, so it writes directly to tty, no stdout
# I run the this demo.rb file like that : doas ./demo.rb
# doas is the replacement of sudo
#
# Commands behavior
# - Get status zero even the command fails
# - stderr is filled on error, so we can filter on this like stderr.empty? to know if there's a failure
# - stdout empty except using system method but can't store stderr
# - i can get stderr (not the full message) using Open3.capture3 but can't get stdout

# remove sl package
cmd = 'pkg_delete sl'

# add sl package
cmd2 = 'pkg_add sl'

# try with a bad package name
cmd3 = 'pkg_add sli'


# sample of commands
cmd = 'pkg_delete sl'
cmd2 = 'pkg_add sl'
cmd3 = 'pkg_add sli'

# using system method, can print stdout but no way to store stderr or stop on error
puts :system_cmd_remove
exit unless system(cmd) => sl-5.02: ok

puts :system_cmd2_add
exit unless system(cmd2) => sl-5.02: ok

puts :system_cmd3_bad
exit unless system(cmd3) => Cant find sli\nopen3_cmd_remove

# Using Open3.capture3, no stdout, can store stderr (not fully)
puts :open3_cmd_remove
stdout, stderr, status = Open3.capture3(cmd)
        puts "stdout : #{stdout}" => stdout :
        puts "stderr : #{stderr}" => stderr :
        puts "status : #{status}" => status : pid 51369 exit 0

puts :open_cmd2_add
stdout, stderr, status = Open3.capture3(cmd2)
        puts "stdout : #{stdout}" => stdout :
        puts "stderr : #{stderr}" => stderr :
        puts "status : #{status}" => status : pid 99908 exit 0

puts :open_cmd3_bad
stdout, stderr, status = Open3.capture3(cmd3)
        puts "stdout : #{stdout}" => stdout :
        puts "stderr : #{stderr}" => stderr : Cant find sli
        puts "status : #{status}" => status : pid 24159 exit 0