thewoolleyman-ruby-pty-check

.ruby-version

ruby-2.3.3

pty_check_test.rb

#!/usr/bin/env ruby

require 'pty'

def process_running?(pid, loop_until_not_alive = false)
  loop do
    Process.getpgid(pid)
    puts "Process with pid #{pid} is running"
    break unless loop_until_not_alive
    sleep 0.5
  end
rescue
  puts "Process with pid #{pid} is NOT running"
end

def process_check(pid, loop_until_not_alive = false)
  loop do
    status = PTY.check(pid)
    puts "PTY::check for process with pid #{pid} is : #{status.inspect}"
    if loop_until_not_alive && !status
      sleep 0.5
    else
      break
    end
  end
end

def output_only_example
  puts "Simple output-only example:\n"
  cmd = 'printf "f"'
  puts "cmd: #{cmd}"
  r, _, pid = PTY.spawn(cmd)
  process_running?(pid) # Process is NOT running...
  process_check(pid) # But STDOUT has not yet been read, so check returns nil
  puts r.gets(1)
  process_check(pid, true) # After STDOUT has not yet been read, check (soon) returns Process::Status
end

def invalid_command_example
  puts "\n\ninvalid command example:"
  cmd = 'exit 42'
  puts "cmd: #{cmd}"

  output_buffer = StringIO.new('')
  PTY.spawn(cmd) do |r, w, pid|

    sleep 0.5 # to give command time to run

    # it will be dead by now
    process_running?(pid, true)
    process_check(pid, true)
    puts output_buffer.string
  end
end

def input_output_example
  puts "\n\ninput + output example - exits when given 'z' on STDIN:"
  cmd = %q(ruby -e 'require "io/console"; while(i=$stdin.getch) do puts ">#{i}<"; if i =~ /z/; break; end; end')
  puts "cmd: #{cmd}"

  output_buffer = StringIO.new('')
  PTY.spawn(cmd) do |r, w, pid|

    sleep 0.5 # to give command time to run

    # it's alive
    process_running?(pid)
    process_check(pid)

    puts 'writing "a"'
    w.putc 'a'
    puts 'reading...'
    a = r.read(3)
    output_buffer.puts(a)
    puts 'output_buffer contents:'
    puts output_buffer.string

    # still alive
    process_running?(pid)
    process_check(pid)

    puts 'writing "z"'
    w.putc 'z'
    sleep 0.5
    puts 'reading...'
    z = r.read(3) # WHY DOESN'T THIS READ '>z<', LIKE IT DOES FROM A REAL TERMINAL?
    sleep 0.5
    output_buffer.puts(z)
    puts 'output_buffer contents:'
    puts output_buffer.string

    # why isn't it dead?
    process_running?(pid)
    process_check(pid)
    puts output_buffer.string
  end
end

# output_only_example
# invalid_command_example
input_output_example