Suppresing Output to Console with Ruby

How to suppress Rails console/irb outputs

You can append ; nil to your statements.

Example:

users = User.all; nil

irb prints the return value of the last executed statement; thus in this case it'll print only nil since nil is the last executed valid statement.

How to suppress the output of return value in IRB/Rails Console?

If you just want to suppress long output once in a while, use ;0, like:

a = [*1..10000];0
# => 0

If you want to suppress it generally, use the ~/.irbrc file. The IRB.conf[:INSPECT_MODE] and IRB.conf[:PROMPT][your_prompt][:RETURN] control what is returned. You can figure out what your_prompt is by checking IRB.conf[:PROMPT_MODE]

Example:

IRB.conf[:PROMPT][:DEFAULT][:RETURN] = "" # suppress return value completely

You'll need to restart irb after changing the value.

Hope that helps.

suppresing output to console with ruby

I use the following snippet in tests to capture and test STDOUT

def capture_stdout(&block)
  original_stdout = $stdout
  $stdout = fake = StringIO.new
  begin
    yield
  ensure
    $stdout = original_stdout
  end
  fake.string
end

With this method, the above would become:

def executing_a_signal
  capture_stdout { a_method(a_signal.new, a_model, a_helper) }
  assert_equal(new_state, a_model.state)
end

Suppressing stubborn console output on system calls in Ruby

Question was answered in the comments. I moved to Open3.capture3 using a format like below and the console text from webp is captured.

stdout, stderr, status = Open3.capture3("convert -flatten \"#{$temp_dir}#{tmp_image_filename}\" \"#{$temp_dir}#{@image_filename}\"")

Avoid printing after executing command in console

I assume you are doing this in the console. I usually add just "; :ok" if I don't want to see the output.

data = YAML.load_file( ... ) ; :ok

Suppress console output during RSpec tests

I suppress puts output in my classes by redirecting $stout to a text file. That way, if I need to see the output for any reason, it is there but it doesn't muddy up my test results.

#spec_helper.rb
RSpec.configure do |config|
  config.before(:all, &:silence_output)
  config.after(:all,  &:enable_output)
end

public
# Redirects stderr and stout to /dev/null.txt
def silence_output
  # Store the original stderr and stdout in order to restore them later
  @original_stderr = $stderr
  @original_stdout = $stdout

  # Redirect stderr and stdout
  $stderr = File.new(File.join(File.dirname(__FILE__), 'dev', 'null.txt'), 'w')
  $stdout = File.new(File.join(File.dirname(__FILE__), 'dev', 'null.txt'), 'w')
end

# Replace stderr and stdout so anything else is output correctly
def enable_output
  $stderr = @original_stderr
  $stdout = @original_stdout
  @original_stderr = nil
  @original_stdout = nil
end

EDIT:

In response to the comment by @MyronMarston, it probably would be smarter to just insert the methods directly into before and after as blocks.

#spec_helper.rb
RSpec.configure do |config|
  original_stderr = $stderr
  original_stdout = $stdout
  config.before(:all) do 
    # Redirect stderr and stdout
    $stderr = File.new(File.join(File.dirname(__FILE__), 'dev', 'null.txt'), 'w')
    $stdout = File.new(File.join(File.dirname(__FILE__), 'dev', 'null.txt'), 'w')
  end
  config.after(:all) do 
    $stderr = original_stderr
    $stdout = original_stdout
  end
end

It looks a little cleaner and keeps methods off of main.
Also, note that if you are using Ruby 2.0, you can use __dir__ instead of File.dirname(__FILE__).

EDIT2

Also it should be mentioned, that you can forward to true os /dev/null by using File::NULL as it was introduced in Ruby v 1.9.3. (jruby 1.7)

Then the code snippet will look as following:

#spec_helper.rb
RSpec.configure do |config|
  original_stderr = $stderr
  original_stdout = $stdout
  config.before(:all) do
    # Redirect stderr and stdout
    $stderr = File.open(File::NULL, "w")
    $stdout = File.open(File::NULL, "w")
  end
  config.after(:all) do
    $stderr = original_stderr
    $stdout = original_stdout
  end
end

Easy way to suppress SQL output in Rails console?

Enter this in the console, or put it in the console's config file:

ActiveRecord::Base.logger = nil

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