# STDIN, OUT, ERR and $stdin, out, err - Differences? **URL:** \ **Category:** Ruby\ **Created:** [June 6, 2009, 3:14am UTC](https://www.ruby-forum.com/t/stdin-out-err-and-stdin-out-err-differences/169639 "2009-06-06T03:14:16Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![terrychou](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ecc23a/32.png) [@terrychou](https://www.ruby-forum.com/u/terrychou)\ **Post date:** [June 6, 2009, 3:14am UTC](https://www.ruby-forum.com/t/stdin-out-err-and-stdin-out-err-differences/169639/1 "2009-06-06T03:14:16Z")
Can anyone explain what’s happening here? print $stdin.fileno =\> 0 print $stdout.fileno =\> 0 print $sterr.fileno =\> 0 print STDIN.fileno =\> 0 print STDOUT.fileno =\> 1 print STDERR.fileno =\> 2 print STDOUT.object\_id =\> 21673330 print $stdout.object\_id =\> 21673330 I get the same results in and out of eclipse and with irb ruby 1.8.6, XP Many thanks. ---
**Author:** ![terrychou](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ecc23a/32.png) [@terrychou](https://www.ruby-forum.com/u/terrychou)\ **Post date:** [June 7, 2009, 12:43am UTC](https://www.ruby-forum.com/t/stdin-out-err-and-stdin-out-err-differences/169639/2 "2009-06-07T00:43:47Z")
Terry C. wrote: > Can anyone explain what’s happening here? > > print $stdin.fileno =\> 0 > print $stdout.fileno =\> 0 > print $sterr.fileno =\> 0 > > print STDIN.fileno =\> 0 > print STDOUT.fileno =\> 1 > print STDERR.fileno =\> 2 > > print STDOUT.object\_id =\> 21673330 > print $stdout.object\_id =\> 21673330 > > I get the same results in and out of eclipse and with irb > > ruby 1.8.6, XP > > Many thanks. Simply, STDIN, STDOUT, STDERR are CONSTANTS and $stdin, $stdout, and $stderr are global variables. They are the same initially but the variables can be re-assigned. ---
**Author:** ![terrychou](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ecc23a/32.png) [@terrychou](https://www.ruby-forum.com/u/terrychou)\ **Post date:** [June 7, 2009, 2:16am UTC](https://www.ruby-forum.com/t/stdin-out-err-and-stdin-out-err-differences/169639/3 "2009-06-07T02:16:45Z")
On Jun 5, 10:14 pm, Terry C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > print STDOUT.object\_id =\> 21673330 > print $stdout.object\_id =\> 21673330 > > I get the same results in and out of eclipse and with irb > > ruby 1.8.6, XP > > Many thanks. Differences between $stdout and STDOUT: [http://blog.segment7.net/articles/2006/08/17/stdout-vs-stdout](http://blog.segment7.net/articles/2006/08/17/stdout-vs-stdout) The bottom line is don’t mess with STDOUT and use $stdout instead. Regards, ---
**Author:** ![terrychou](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ecc23a/32.png) [@terrychou](https://www.ruby-forum.com/u/terrychou)\ **Post date:** [June 7, 2009, 7:34pm UTC](https://www.ruby-forum.com/t/stdin-out-err-and-stdin-out-err-differences/169639/4 "2009-06-07T19:34:41Z")
Terry C. wrote: > Can anyone explain what’s happening here? > > print $stdin.fileno =\> 0 > print $stdout.fileno =\> 0 > print $sterr.fileno =\> 0 Copy-paste error? The third line is clearly a typo for $stderr, and under Linux at least these give 0, 1, 2 respectively. ---
**Author:** ![terrychou](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ecc23a/32.png) [@terrychou](https://www.ruby-forum.com/u/terrychou)\ **Post date:** [June 8, 2009, 2:39pm UTC](https://www.ruby-forum.com/t/stdin-out-err-and-stdin-out-err-differences/169639/5 "2009-06-08T14:39:48Z")
Janos S. wrote: > On Sun, Jun 7, 2009 at 7:34 PM, Brian C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > wrote: > > > Copy-paste error? The third line is clearly a typo for $stderr, and > > under Linux at least these give 0, 1, 2 respectively. > > I can confirm this is true on WinXP, Ruby 1.8.7 and 1.9.1 That makes no sense. The OP said that $stdout.fileno != STDOUT.fileno, and yet $stdout.object\_id == STDOUT.object\_id It can’t be the same object, but respond to the same method differently. What do you get from this? Run it as a standalone ruby script, not within irb, to eliminate irb as the source of the problem. puts STDOUT.fileno puts $stdout.fileno puts STDOUT.inspect puts $stdout.inspect # and repeat for STDERR/$stderr ---
**Author:** ![terrychou](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ecc23a/32.png) [@terrychou](https://www.ruby-forum.com/u/terrychou)\ **Post date:** [June 8, 2009, 10:00am UTC](https://www.ruby-forum.com/t/stdin-out-err-and-stdin-out-err-differences/169639/6 "2009-06-08T10:00:59Z")
On Sun, Jun 7, 2009 at 7:34 PM, Brian C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > ## Copy-paste error? The third line is clearly a typo for $stderr, and under Linux at least these give 0, 1, 2 respectively. > > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). I can confirm this is true on WinXP, Ruby 1.8.7 and 1.9.1 ---
**Author:** ![terrychou](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ecc23a/32.png) [@terrychou](https://www.ruby-forum.com/u/terrychou)\ **Post date:** [June 9, 2009, 7:48am UTC](https://www.ruby-forum.com/t/stdin-out-err-and-stdin-out-err-differences/169639/7 "2009-06-09T07:48:47Z")
> > Maybe I misunderstood, and you were confirming my interpretation to be > > true, not the OP’s 🙂 😉 Yes, I meant you were right; it’s working as intended (0, 1, 2 ) on windows. ---
**Author:** ![terrychou](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ecc23a/32.png) [@terrychou](https://www.ruby-forum.com/u/terrychou)\ **Post date:** [June 8, 2009, 2:50pm UTC](https://www.ruby-forum.com/t/stdin-out-err-and-stdin-out-err-differences/169639/8 "2009-06-08T14:50:18Z")
Brian C. wrote: > Janos S. wrote: > > > On Sun, Jun 7, 2009 at 7:34 PM, Brian C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > > wrote: > > > > > Copy-paste error? The third line is clearly a typo for $stderr, and > > > under Linux at least these give 0, 1, 2 respectively. > > > > I can confirm this is true on WinXP, Ruby 1.8.7 and 1.9.1 Maybe I misunderstood, and you were confirming my interpretation to be true, not the OP’s 🙂 Anyway I’ve just booted a laptop into XP, and done this: C:\>ruby puts STDOUT.fileno puts $stdout.fileno puts STDOUT.inspect puts $stdout.inspect puts STDERR.fileno puts $stderr.fileno puts STDERR.inspect puts $stderr.inspect ^Z 1 1 #IO:0x2846af0 #IO:0x2846af0 2 2 #IO:0x2846adc #IO:0x2846adc C:\>ruby -v ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32] This version of Ruby came from the ‘one-click installer’ Ruby-186-26 And FWIW, I get the same in irb too. HTH, Brian.