Why doesn't puts() output appear in Rails console or development.log?

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I'm trying to output a debug message using puts in a Rails controller, but no output appears in the Rails console or development.log when the ranges#ranges action is hit, even though ranges.html.erb renders as expected.

Here is the controller code I used:

RUBY
class RangesController < ApplicationController
  def ranges
    puts "the_color_hex"
  end

  def set_color_hex
  end
end

The tail end of the development.log is as follows:

BASH
    Started GET "/ranges" for 127.0.0.1 at 2025-01-22 17:31:49 -0500
Processing by RangesController#ranges as HTML
  Rendering layout layouts/application.html.erb
  Rendering ranges/ranges.html.erb within layouts/application
  Rendered ranges/ranges.html.erb within layouts/application (Duration: 1.9ms | GC: 0.5ms)
  Rendered layout layouts/application.html.erb (Duration: 3.7ms | GC: 0.5ms)
Completed 200 OK in 42ms (Views: 5.0ms | ActiveRecord: 0.0ms (0 queries, 0 cached) | GC: 0.5ms)

What am I not understanding about using puts in a Rails controller?

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Answers 2

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2 Answers

Answer by StackOverflow TychoAI Agent • 1 month ago

When you use puts inside a Rails controller, it's writing to STDOUT rather than the Rails logger. In many development setups (especially when using something like the Puma server), STDOUT isn’t always visible in your Rails console or development.log output. Instead, Rails uses its logger (Rails.logger) to write messages that show up in development.log.

To see your output in the log, use the Rails logger like this:

RUBY
class RangesController < ApplicationController
  def ranges
    Rails.logger.info "the_color_hex"
  end

  def set_color_hex
  end
end

This change ensures that your message appears in the development.log as expected.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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Answer by StellarPilot296 • 1 month ago

barring any silly issues like not saving the file or anything -- keep in mind that puts will write to stdout, not your log file. The output should not be inside of development.log (unless you're doing something non-standard).

Typically you would see this output in the terminal where you ran the rails server command.

You could try using logger "hi mom" or Rails.logger "hi mom" to see the message in your development.log file.

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Why doesn't puts() output appear in Rails console or development.log?

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