# Re: Can you temporarily turn off STDERR?

**URL:** <https://www.ruby-forum.com/t/re-can-you-temporarily-turn-off-stderr/66499>\
**Category:** Ruby\
**Created:** [August 26, 2006, 11:58am UTC](https://www.ruby-forum.com/t/re-can-you-temporarily-turn-off-stderr/66499 "2006-08-26T11:58:54Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![BergerS\_Daniel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/bc8723/32.png) [@BergerS\_Daniel](https://www.ruby-forum.com/u/BergerS_Daniel)\
**Post date:** [August 26, 2006, 11:58am UTC](https://www.ruby-forum.com/t/re-can-you-temporarily-turn-off-stderr/66499/1 "2006-08-26T11:58:54Z")

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> > 
> 
> can’t change
> 
> [http://codeforpeople.com/lib/ruby/session/session-2.4.0/README](http://codeforpeople.com/lib/ruby/session/session-2.4.0/README)  
> [http://codeforpeople.com/lib/ruby/open4/open4-0.5.1/README](http://codeforpeople.com/lib/ruby/open4/open4-0.5.1/README)
> 
> in particular the Open4::spawn command. both are available as

This comes up often enough that I wonder if allowing IO#reopen to take a  
block would be a good idea:

$stderr.reopen(‘/dev/null’) do

# Code here redirects to /dev/null

end

# Code outside the block behaves normally

I thought this idea had been brought up before, and that there was some  
downside to this, but I can’t find any references to it now.

Thoughts?

- Dan

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<div class="post-metadata">

**Author:** ![BergerS\_Daniel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/bc8723/32.png) [@BergerS\_Daniel](https://www.ruby-forum.com/u/BergerS_Daniel)\
**Post date:** [September 4, 2006, 2:46pm UTC](https://www.ruby-forum.com/t/re-can-you-temporarily-turn-off-stderr/66499/2 "2006-09-04T14:46:14Z")

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On 8/25/06, Berger, Daniel [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> I thought this idea had been brought up before, and that there was some  
> downside to this, but I can’t find any references to it now.
> 
> Thoughts?
> 
> - Dan

How about this?

#!/usr/bin/env ruby

# reopen\_with\_block.rb

class IO

alias\_method :\_orig\_reopen, :reopen

def reopen(\*args)  
if block\_given?  
is\_path = args.length == 2  
path\_or\_io, mode\_str = args  
old\_io = clone  
path\_or\_io = File.open(path\_or\_io, mode\_str || “w”) if is\_path  
\_orig\_reopen(path\_or\_io)  
begin  
yield  
ensure  
\_orig\_reopen(old\_io)  
path\_or\_io.close if is\_path  
end  
else  
\_orig\_reopen(\*args)  
end  
end

end

if $0 == **FILE**  
$stderr.reopen(‘error\_log’, ‘w’) do  
$stderr.puts “Stuff on error”  
puts “normal stuff”  
end

File.open(‘error\_log\_2’, “w”) do |file|  
$stderr.reopen(file) do  
$stderr.puts “Stuff on error 2”  
puts “normal stuff 2”  
end  
end

$stderr.reopen(‘/dev/null’) do  
$stderr.puts “Stuff on error 3”  
puts “normal stuff 3”  
end

# Make sure old way works

old\_stderr = $stderr.clone  
File.open(‘error\_log\_4’, ‘w’) do |log\_file|  
$stderr.reopen(log\_file)  
begin  
$stderr.puts “Stuff on error 4”  
puts “normal stuff 4”  
ensure  
$stderr.reopen(old\_stderr)  
end  
end

begin  
$stderr.reopen(‘error\_log\_5’, ‘w’) do  
$stderr.puts “Stuff on error 5”  
puts “normal stuff 5”  
raise “This message courtesy of raise”  
end  
rescue =\> e  
puts e  
end

end

---

<div class="post-metadata">

**Author:** ![BergerS\_Daniel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/bc8723/32.png) [@BergerS\_Daniel](https://www.ruby-forum.com/u/BergerS_Daniel)\
**Post date:** [September 4, 2006, 2:46pm UTC](https://www.ruby-forum.com/t/re-can-you-temporarily-turn-off-stderr/66499/3 "2006-09-04T14:46:14Z")

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> downside to this, but I can’t find any references to it now.
> 
> Thoughts?

Can’t handle threading sanely, for one.