# Ignore printout **URL:** \ **Category:** Ruby\ **Created:** [October 12, 2007, 4:40am UTC](https://www.ruby-forum.com/t/ignore-printout/117021 "2007-10-12T04:40:57Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Fredrik](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/cab0a1/32.png) [@Fredrik](https://www.ruby-forum.com/u/Fredrik)\ **Post date:** [October 12, 2007, 4:40am UTC](https://www.ruby-forum.com/t/ignore-printout/117021/1 "2007-10-12T04:40:57Z")
I am using a compiled C-code in my Ruby program. The problem is that the C-code prints some messages that I don’t want to show in my Ruby program. What would be the best way to get rid of these printouts? I don’t want to get into the original C-code and take away the print commands since that is not my code. Are the printouts sent directly to standard output, meaning there is no way for Ruby to interfere? Thanks for any help! /Fredrik ---
**Author:** ![Fredrik](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/cab0a1/32.png) [@Fredrik](https://www.ruby-forum.com/u/Fredrik)\ **Post date:** [October 12, 2007, 5:55am UTC](https://www.ruby-forum.com/t/ignore-printout/117021/2 "2007-10-12T05:55:44Z")
Fredrik wrote: > I am using a compiled C-code in my Ruby program. The problem is that > the C-code prints some messages that I don’t want to show in my Ruby > program. What would be the best way to get rid of these printouts? > > I don’t want to get into the original C-code and take away the print > commands since that is not my code. Are the printouts sent directly to > standard output, meaning there is no way for Ruby to interfere? You may try to redirect $stdout while the C code runs - I’m not sure this will work, but it’s worth a try. mortee ---
**Author:** ![Fredrik](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/cab0a1/32.png) [@Fredrik](https://www.ruby-forum.com/u/Fredrik)\ **Post date:** [October 12, 2007, 6:18am UTC](https://www.ruby-forum.com/t/ignore-printout/117021/3 "2007-10-12T06:18:31Z")
On Oct 11, 2007, at 19:40 , Fredrik wrote: > I am using a compiled C-code in my Ruby program. The problem is that > the C-code prints some messages that I don’t want to show in my Ruby > program. What would be the best way to get rid of these printouts? > > I don’t want to get into the original C-code and take away the print > commands since that is not my code. Are the printouts sent directly to > standard output, meaning there is no way for Ruby to interfere? You will need to reopen STDOUT to /dev/null ---
**Author:** ![Fredrik](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/cab0a1/32.png) [@Fredrik](https://www.ruby-forum.com/u/Fredrik)\ **Post date:** [October 12, 2007, 8:05am UTC](https://www.ruby-forum.com/t/ignore-printout/117021/4 "2007-10-12T08:05:27Z")
I should clarify myself: I was expecting to find that STDOUT is a constant so that I could do: $stdout.reopen(File.new(’/dev/null’,‘w’)) puts ‘Nobody can see this.’ $stdout.reopen(STDOUT) But after the first line, my STDOUT is pointing to the exact same place as $stdout. Isn’t that weird? ---
**Author:** ![Fredrik](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/cab0a1/32.png) [@Fredrik](https://www.ruby-forum.com/u/Fredrik)\ **Post date:** [October 12, 2007, 8:50am UTC](https://www.ruby-forum.com/t/ignore-printout/117021/5 "2007-10-12T08:50:31Z")
Well, this does the trick (note the ‘clone’ instruction on line 1). It seems to be working nicely also for the compiled binary that I am calling. out = $stdout.clone $stdout.reopen(File.new(’/dev/null’,‘w’)) puts ‘You cant see this!’ $stdout.reopen(out) I am still confused over why STDOUT is not a constant though… Thanks for your pointers! ---
**Author:** ![Fredrik](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/cab0a1/32.png) [@Fredrik](https://www.ruby-forum.com/u/Fredrik)\ **Post date:** [October 12, 2007, 7:48am UTC](https://www.ruby-forum.com/t/ignore-printout/117021/6 "2007-10-12T07:48:31Z")
> You will need to reopen STDOUT to /dev/null Then I have two more questions to that 🙂 1. What’s the difference between $stdout and STDOUT? They seem to be the same thing. 2. In my pickaxe book I read that “Assignment to $stdout is depracated; use $stdout.reopen instead.” But if I want to redirect $stdout and then $direct it back to what it was before, surely I HAVE to use assignment to $stdout. Like this: out = $stdout $stdout = File.new(’/dev/null’,‘w’) puts ‘This is not to be seen by anybody.’ $stdout.reopen(out) If I use reopen on the second line instead, the ‘out’ variable comes along to this new value and nobody knows where the “usual stdout” is, right? ---
**Author:** ![Fredrik](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/cab0a1/32.png) [@Fredrik](https://www.ruby-forum.com/u/Fredrik)\ **Post date:** [October 12, 2007, 2:42pm UTC](https://www.ruby-forum.com/t/ignore-printout/117021/7 "2007-10-12T14:42:40Z")
Fredrik wrote: > out = $stdout > $stdout = File.new(’/dev/null’,‘w’) > puts ‘This is not to be seen by anybody.’ > $stdout.reopen(out) Only as an remark - on Windows you should use $stdout = File.open(“nul:”, “w”) to ignore Output, and $stdout = STDOUT to reset. Wolfgang Nádasi-Donner ---
**Author:** ![Fredrik](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/cab0a1/32.png) [@Fredrik](https://www.ruby-forum.com/u/Fredrik)\ **Post date:** [October 12, 2007, 12:44pm UTC](https://www.ruby-forum.com/t/ignore-printout/117021/8 "2007-10-12T12:44:04Z")
Fredrik wrote: > I am still confused over why STDOUT is not a constant though… > Thanks for your pointers! I’d guess that when you reopen a stream, then it as an object remains the same, just what you send it will end up somewhere else than before. In contrast, when you assign to a variable, the object itself changes which that variable references. Since $stdout and STDOUT initially point to the same object, if you dont assign $stdout, instead you modify the onject itself, the two continue to reference the same original object. Remember that you can modify a constant object’s state without any warning anyway, so you could even reopen STDOUT itself. mortee ---
**Author:** ![Fredrik](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/cab0a1/32.png) [@Fredrik](https://www.ruby-forum.com/u/Fredrik)\ **Post date:** [October 12, 2007, 6:45pm UTC](https://www.ruby-forum.com/t/ignore-printout/117021/9 "2007-10-12T18:45:06Z")
On Oct 11, 2007, at 22:45 , Fredrik wrote: > > You will need to reopen STDOUT to /dev/null > > Then I have two more questions to that 🙂 > > 1. What’s the difference between $stdout and STDOUT? They seem to be > the same thing. [http://blog.segment7.net/articles/2006/08/17/stdout-vs-stdout](http://blog.segment7.net/articles/2006/08/17/stdout-vs-stdout) In your case you want to reopen STDOUT because somebody using your code may have changed $stdout, if they want to capture or redirect output. > 1. In my pickaxe book I read that “Assignment to $stdout is > depracated; use $stdout.reopen instead.” But if I want to redirect > $stdout and then $direct it back to what it was before, surely I HAVE > to use assignment to $stdout. Like this: I don’t think this is true anymore. You can’t reopen using StringIO to capture regular ruby puts or p. > out = $stdout > $stdout = File.new(‘/dev/null’,‘w’) > puts ‘This is not to be seen by anybody.’ > $stdout.reopen(out) > > If I use reopen on the second line instead, the ‘out’ variable comes > along to this new value and nobody knows where the “usual stdout” is, > right? Right, you should dup $stdout there.