thewoolleyman-ruby-pty-check

.ruby-version

ruby-2.3.3

output.txt

input + output example - exits when given 'z' on STDIN:
cmd: ruby -e 'require "io/console"; while(i=$stdin.getch) do puts ">#{i}<"; if i == "z"; break; end; end'
Process with pid 80672 is running
PTY::check for process with pid 80672 is : nil
writing "a"
not ready to read, sleeping...
ready to read...
reading...
Read char '>' (ASCII  62) and wrote to output buffer
output_buffer contents:
>
reading...
Read char 'a' (ASCII  97) and wrote to output buffer
output_buffer contents:
>a
reading...
Read char '<' (ASCII  60) and wrote to output buffer
output_buffer contents:
>a<
reading...
Read char '' (ASCII  13) and wrote to output buffer
output_buffer contents:
>a<
reading...
Read char '
' (ASCII  10) and wrote to output buffer
output_buffer contents:
>a<
not attempting to read, not ready...
Process with pid 80672 is running
PTY::check for process with pid 80672 is : nil
writing "z"
not ready to read, sleeping...
ready to read...
reading...
Read char '>' (ASCII  62) and wrote to output buffer
output_buffer contents:
>a<
>
reading...
Read char 'z' (ASCII 122) and wrote to output buffer
output_buffer contents:
>a<
>z
reading...
Read char '<' (ASCII  60) and wrote to output buffer
output_buffer contents:
>a<
>z<
reading...
Read char '' (ASCII  13) and wrote to output buffer
output_buffer contents:
>a<
>z<
reading...
Read char '
' (ASCII  10) and wrote to output buffer
output_buffer contents:
>a<
>z<
not attempting to read, not ready...
Process with pid 80672 is NOT running
PTY::check for process with pid 80672 is : #<Process::Status: pid 80672 exit 0>
>a<
>z<

Process finished with exit code 0

pty_check_test.rb

#!/usr/bin/env ruby

require 'pty'
require 'io/wait'

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 wait_for_read_to_read(r)
  loop do
    unless r.ready?
      puts 'not ready to read, sleeping...'
      sleep 0.5
      redo
    end
    puts 'ready to read...'
    break
  end
end

def read_chars_to_output_buffer(r, output_buffer)
  loop do
    unless r.ready?
      puts 'not attempting to read, not ready...'
      break
    end
    puts 'reading...'
    char = r.read(1)
    puts "Read char '#{char unless char.ord == 13}' (ASCII %3d) and wrote to output buffer" % char.ord
    output_buffer.putc(char)
    puts 'output_buffer contents:'
    puts output_buffer.string
  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'
    wait_for_read_to_read(r)
    read_chars_to_output_buffer(r, output_buffer)

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

    puts 'writing "z"'
    w.putc 'z'
    wait_for_read_to_read(r)
    read_chars_to_output_buffer(r, output_buffer)

    # 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