The document discusses various methods to run external processes from Ruby, focusing on different libraries like io::popen, kernel::open, systemu, and others. It highlights the capabilities and limitations of each method regarding real-time input/output handling and compatibility with Windows and other environments. The presentation also emphasizes the use of processpilot for better process management and features like timeout mechanisms.

1. Piloting processes through standard I/O in Ruby Jan 25 th 2012 Muriel Salvan Open Source Lead developer and architect X-Aeon Solutions http://x-aeon.com

2. The needs Run external processes from Ruby Access their stdin/out/err in real time (follow their execution tightly) Work on both Unix and Windows Work also with external Ruby programs

3. Solutions tested IO::popen

4. Kernel::open

5. systemu

6. PTY::spawn

7. ChildProcess

8. Open3::popen3

9. ProcessPilot

10. Aruba (used with Cucumber )

11. External test program This is Line 1, before sleep 1

12. This is Line 2, after sleep 1

13. Enter string 1: My String 1

14. String 1 entered: My String 1

15. This is Line 1 on STDERR, before sleep 1

16. This is Line 2 on STDERR, after sleep 1

17. Enter string 2 from STDERR: My String 2

18. String 2 entered: My String 2

19. This is Line 3, before sleep 1

20. This is Line 4, after sleep 1 Output : Output on STDOUT only Output : Output on STDERR only Output : Output for interactive tests only Input : Input taken from STDIN sleep 1 sleep 1 sleep 1 Input from stdin Input from stdin

21. IO::popen IO . popen ( 'ruby test.rb' , 'r+' ) do | io | io . write ( "My String 1 \n My String 2 \n " ) io . close_write puts "stdout: #{io.read}” end

22. IO::popen stdin must be closed before accessing stdout => No real time

23. stderr support only for Ruby > 1.9

24. stderr support does not work on Windows

25. Does not work with Ruby programs that don't explicitly turn off stdout internal cache

26. Kernel::open Kernel :: open ( '|ruby test.rb', 'r+' ) do | io | puts io . gets # stdout Line 1 puts io . gets # stdout Line 2 puts io . read ( 31 ) # stdout Prompt sleep 1 io . write ( "My String 1 \n " ) puts io . gets # stdout String 1 sleep 1 io . write ( "My String 2 \n " ) puts io . gets # stdout Line 3 puts io . gets # stdout Line 4 end

27. Kernel::open stdin and stdout can be written and read in real time No support for stderr

28. Does not work with Ruby programs that don't explicitly turn off stdout internal cache

29. systemu require 'systemu' status, stdout, stderr = systemu ( 'ruby test.rb' , 0 => "My String 1 \n My String 2 \n " ) puts "stdout: #{stdout}" puts "stderr: #{stderr}"

30. systemu Handle stderr Does not work on Windows

31. stdin must be given to the process at startup time => No real time

32. stdout/err can only be accessed when process has exited => No real time

33. PTY::spawn require 'pty' PTY ::spawn ( 'ruby test.rb' ) do | stdout, stdin, pid | puts stdout. gets # stdout Line 1 puts stdout. gets # stdout Line 2 puts stdout. read ( 31 ) # stdout Prompt sleep 1 stdin. write ( "My String 1 \n " ) puts stdout. gets # Extra for input echoed puts stdout. gets # stdout String 1 puts stdout. gets # Should be on stderr puts stdout. gets # Should be on stderr puts stdout. read ( 43 ) # Should be on stderr sleep 1 stdin. write ( "My String 2 \n " ) puts stdout. gets # Extra for input echoed puts stdout. gets # Should be on stderr puts stdout. gets # stdout Line 3 puts stdout. gets # stdout Line 4 end

34. PTY::spawn stdin and stdout can be written and read in real time Does not exist on Windows

35. Mix stdout and stderr in the same IO => No stderr support

36. Echoes all input from stdin to stdout

37. ChildProcess require 'childprocess' require 'tempfile' lProcess = ChildProcess. build ( 'ruby' , 'test.rb' ) lProcess. duplex = true Tempfile . open ( 'stdout' ) do | oStdOUT | lProcess. io . stdout = oStdOUT Tempfile . open ( 'stderr' ) do | oStdERR | lProcess. io . stderr = oStdERR lProcess. start stdout = File . open ( oStdOUT. path , 'r' ) stderr = File . open ( oStdERR. path , 'r' ) stdin = lProcess. io . stdin waitfor ( stdout, 'This is Line 2' ) # Need active wait sleep 1 stdin. write ( "My String 1 \n " ) waitfor ( stderr, 'This is Line 2' ) # Need active wait sleep 1 stdin. write ( "My String 2 \n " ) waitfor ( stdout, 'This is Line 4' ) # Need active wait end end

38. ChildProcess All stdin/out/err can be written/read in real time Need stdout/err redirections to files on Windows

39. Need active blocking read on stdout and stderr to wait for next line

40. Very unstable on native Windows

41. Does not work with Ruby programs that don't explicitly turn off stdout internal cache

42. Open3::popen3 require 'open3' Open3 ::popen3 ( 'ruby test.rb' ) do | stdin, stdout, stderr, wait_thr | puts stdout. gets # stdout Line 1 puts stdout. gets # stdout Line 2 puts stdout. read ( 31 ) # stdout Prompt sleep 1 stdin. write ( "My String 1 \n " ) puts stdout. gets # stdout String 1 puts stderr. gets # stderr Line 1 puts stderr. gets # stderr Line 2 puts stderr. read ( 43 ) # stderr Prompt sleep 1 stdin. write ( "My String 2 \n " ) puts stderr. gets # stderr String 2 puts stdout. gets # stdout Line 3 puts stdout. gets # stdout Line 4 end

43. Open3::popen3 All stdin/out/err can be written/read in real time

44. Works on any OS

45. No need for files redirection Does not work with Ruby programs that don't explicitly turn off stdout internal cache

46. ProcessPilot require 'processpilot/processpilot' ProcessPilot ::pilot ( 'ruby' , 'test.rb' ) do | stdin, stdout, stderr, childproc | puts stdout. gets # stdout Line 1 puts stdout. gets # stdout Line 2 puts stdout. read ( 31 ) # stdout Prompt sleep 1 stdin. write ( "My String 1 \n " ) puts stdout. gets # stdout String 1 puts stderr. gets # stderr Line 1 puts stderr. gets # stderr Line 2 puts stderr. read ( 43 ) # stderr Prompt sleep 1 stdin. write ( "My String 2 \n " ) puts stderr. gets # stderr String 2 puts stdout. gets # stdout Line 3 puts stdout. gets # stdout Line 4 end

47. ProcessPilot All stdin/out/err can be written/read in real time

48. Works on any OS

49. Works with all Ruby programs , even if they don't explicitly turn off stdout internal cache

50. Provides time-out mechanisms in its API

51. ProcessPilot Time outs: stdout. gets ( :TimeOutSecs => 5 ) Deactivate Ruby cache: ProcessPilot ::pilot ( 'test.rb', :ForceRubyProcessSync => true ) do | stdin, stdout, stderr, childproc | # … end

52. Aruba When I run `ruby test.rb` interactively And I type "My String 1" And I type "My String 2" Then the stdout should contain : """ This is Line 1, before sleep 1 This is Line 2, after sleep 1 Enter string 1: String 1 entered: My String 1 This is Line 3, before sleep 1 This is Line 4, after sleep 1 """ And the stderr should contain : " "" This is Line 1 on STDERR, before sleep 1 This is Line 2 on STDERR, after sleep 1 Enter string 2 from STDERR: String 2 entered: My String 2 """

53. Aruba Handle stderr correctly

54. Works on any OS

55. Works with all Ruby programs , even if they don't explicitly turn off stdout internal cache All stdin has to be entered at the beginning of the scenario: No real time

56. No easy way to test for lines sequence between stdout and stderr flows

57. Links IO::popen

58. Kernel::open

59. systemu

60. PTY::spawn

61. ChildProcess

62. Open3::popen3

63. ProcessPilot

64. Aruba (used with Cucumber ) This presentation is available under CC-BY license by Muriel Salvan

65. Q/A