Piloting processes through std IO at the Ruby Drink-up of Sophia, January 2012

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

4. Kernel::open

5. systemu

6. PTY::spawn

7. ChildProcess

8. Open3::popen3

9. ProcessPilot

10. Aruba (used with Cucumber )

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 My String 2 " ) io . close_write puts "stdout: #{io.read}” end

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 " ) puts io . gets # stdout String 1 sleep 1 io . write ( "My String 2 " ) puts io . gets # stdout Line 3 puts io . gets # stdout Line 4 end

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

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 " ) 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 " ) 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

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 " ) waitfor ( stderr, 'This is Line 2' ) # Need active wait sleep 1 stdin. write ( "My String 2 " ) waitfor ( stdout, 'This is Line 4' ) # Need active wait end end

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

40. Very unstable on native Windows

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 " ) 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 " ) puts stderr. gets # stderr String 2 puts stdout. gets # stdout Line 3 puts stdout. gets # stdout Line 4 end

44. Works on any OS

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 " ) 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 " ) puts stderr. gets # stderr String 2 puts stdout. gets # stdout Line 3 puts stdout. gets # stdout Line 4 end

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

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 """

54. Works on any OS

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

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

Piloting processes through std IO at the Ruby Drink-up of Sophia, January 2012

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