Ruby method to execute and continuously print output of long-running shell command

long_running_exec.rb

#!/usr/bin/ruby
require "open4"

def shell_exec(command)
  puts("> " + command + "\n")
  pid, stdin, stdout, stderr = Open4::popen4(command)
  while Process::waitpid(pid, Process::WNOHANG).nil? do
    stdout.each_line { |line| puts line }
    stderr.each_line { |line| puts line }
    sleep(1)
  end
  stdout.each_line { |line| puts line }
  stderr.each_line { |line| puts line }
end

# shell_exec("ls -l && sleep 5 && ls -l && sleep 2")

Thank you for that, here is a similar one with Open3:

#!/usr/bin/env ruby
# frozen_string_literal: true

require 'open3'

def find
  Open3.popen3('find .') do |_stdin, stdout, stderr, wait_thr|
    pid = wait_thr.pid
    begin
      while Process.waitpid(pid, Process::WNOHANG).nil?
        stdout.each_line { |line| yield line.strip }
        stderr.each_line { |line| puts line.strip }
        sleep(0.5)
      end
    rescue Errno::ECHILD # in case process exits very quickly
    end
    stdout.each_line { |line| yield line.strip }
    stderr.each_line { |line| puts line.strip }
  end
end

find do |path|
  p path
end