blocks|key|645618|text|@David的解决方案非常好。我已经根据他的代码为多个目标创建了一个通用的委托类。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|645619|require+'logger'

class+MultiDelegator
++def+initialize(*targets)
++++@targets+=+targets
++end

++def+self.delegate(*methods)
++++methods.each+do+%7Cm%7C
++++++define_method(m)+do+%7C*args%7C
++++++++@targets.map+{+%7Ct%7C+t.send(m,+*args)+}
++++++end
++++end
++++self
++end

++class+<<self
++++alias+to+new
++end
end

log_file+=+File.open("debug.log",+"a")
log+=+Logger.new+MultiDelegator.delegate(:write,+:close).to(STDOUT,+log_file)|code-block|syntax|javascript|645620|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

@David's solution is very good. I've made a generic delegator class for multiple targets based on his code.

<pre><code>require 'logger'

class MultiDelegator
 def initialize(*targets)
 @targets = targets
 end

 def self.delegate(*methods)
 methods.each do |m|
 define_method(m) do |*args|
 @targets.map { |t| t.send(m, *args) }
 end
 end
 self
 end

 class &lt;&lt;self
 alias to new
 end
end

log_file = File.open("debug.log", "a")
log = Logger.new MultiDelegator.delegate(:write, :close).to(STDOUT, log_file)
</code></pre>

blocks|key|645648|text|您还可以将多个设备日志记录功能直接添加到记录器中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|645649|require+'logger'

class+Logger
++#+Creates+or+opens+a+secondary+log+file.
++def+attach(name)
++++@logdev.attach(name)
++end

++#+Closes+a+secondary+log+file.
++def+detach(name)
++++@logdev.detach(name)
++end

++class+LogDevice+#+:nodoc:
++++attr_reader+:devs

++++def+attach(log)
++++++@devs+%7C%7C=+{}
++++++@devs[log]+=+open_logfile(log)
++++end

++++def+detach(log)
++++++@devs+%7C%7C=+{}
++++++@devs[log].close
++++++@devs.delete(log)
++++end

++++alias_method+:old_write,+:write
++++def+write(message)
++++++old_write(message)

++++++@devs+%7C%7C=+{}
++++++@devs.each+do+%7Clog,+dev%7C
++++++++dev.write(message)
++++++end
++++end
++end
end|code-block|syntax|javascript|645650|例如：|645651|logger+=+Logger.new(STDOUT)
logger.warn('This+message+goes+to+stdout')

logger.attach('logfile.txt')
logger.warn('This+message+goes+both+to+stdout+and+logfile.txt')

logger.detach('logfile.txt')
logger.warn('This+message+goes+just+to+stdout')|645652|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You can also add multiple device logging functionality directly into the Logger:

<pre><code>require 'logger'

class Logger
 # Creates or opens a secondary log file.
 def attach(name)
 @logdev.attach(name)
 end

 # Closes a secondary log file.
 def detach(name)
 @logdev.detach(name)
 end

 class LogDevice # :nodoc:
 attr_reader :devs

 def attach(log)
 @devs ||= {}
 @devs[log] = open_logfile(log)
 end

 def detach(log)
 @devs ||= {}
 @devs[log].close
 @devs.delete(log)
 end

 alias_method :old_write, :write
 def write(message)
 old_write(message)

 @devs ||= {}
 @devs.each do |log, dev|
 dev.write(message)
 end
 end
 end
end
</code></pre>

For instance:

<pre><code>logger = Logger.new(STDOUT)
logger.warn('This message goes to stdout')

logger.attach('logfile.txt')
logger.warn('This message goes both to stdout and logfile.txt')

logger.detach('logfile.txt')
logger.warn('This message goes just to stdout')
</code></pre>

blocks|key|862903|text|虽然我很喜欢其他建议，但我发现我也有同样的问题，但我希望能够为STDERR和文件提供不同的日志记录级别。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|862904|我最终采用了一种在记录器级别而不是IO级别进行多路复用的路由策略，这样每个记录器就可以在独立的日志级别上操作：|862905|class+MultiLogger
++def+initialize(*targets)
++++@targets+=+targets
++end

++%25w(log+debug+info+warn+error+fatal+unknown).each+do+%7Cm%7C
++++define_method(m)+do+%7C*args%7C
++++++@targets.map+{+%7Ct%7C+t.send(m,+*args)+}
++++end
++end
end

stderr_log+=+Logger.new(STDERR)
file_log+=+Logger.new(File.open('logger.log',+'a'))

stderr_log.level+=+Logger::INFO
file_log.level+=+Logger::DEBUG

log+=+MultiLogger.new(stderr_log,+file_log)|code-block|syntax|javascript|862906|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

While I quite like the other suggestions, I found I had this same issue but wanted the ability to have different logging levels for STDERR and the file. 

I ended up with a routing strategy that multiplexes at the logger level rather than at the IO level, so that each logger could then operate at independent log-levels:

<pre class="lang-rb prettyprint-override"><code>class MultiLogger
 def initialize(*targets)
 @targets = targets
 end

 %w(log debug info warn error fatal unknown).each do |m|
 define_method(m) do |*args|
 @targets.map { |t| t.send(m, *args) }
 end
 end
end

stderr_log = Logger.new(STDERR)
file_log = Logger.new(File.open('logger.log', 'a'))

stderr_log.level = Logger::INFO
file_log.level = Logger::DEBUG

log = MultiLogger.new(stderr_log, file_log)
</code></pre>

blocks|key|862951|text|我采用了其他人已经研究过的“将所有方法委托给子元素”的相同想法，但为每个方法返回了上次调用该方法的返回值。如果我没有这样做，它就会破坏logger-colors，因为它期望返回一个Integer，而map返回一个Array。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|862952|class+MultiIO
++def+self.delegate_all
++++IO.methods.each+do+%7Cm%7C
++++++define_method(m)+do+%7C*args%7C
++++++++ret+=+nil
++++++++@targets.each+{+%7Ct%7C+ret+=+t.send(m,+*args)+}
++++++++ret
++++++end
++++end
++end

++def+initialize(*targets)
++++@targets+=+targets
++++MultiIO.delegate_all
++end
end|code-block|syntax|javascript|862953|这将把每个方法重新委托给所有目标，并且只返回最后一次调用的返回值。|862954|此外，如果你想要颜色，STDOUT或STDERR必须放在最后，因为它是唯一两种应该输出的last颜色。但是，它还会将颜色输出到您的文件中。|862955|logger+=+Logger.new+MultiIO.new(File.open("log/test.log",+'w'),+STDOUT)
logger.error+"Roses+are+red"
logger.unknown+"Violets+are+blue"|862956|entityMap^0|1V|D|2I|7|2Y|5|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|11|8|@]|D|@]|E|$]]|$1|O|3|P|5|H|7|12|8|@]|D|@]|E|$I|J]]|$1|Q|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|R|$]]

I went to the same idea of "Delegating all methods to sub-elements" that other people already explored, but am returning for each of them the return value of the last call of the method.
If I didn't, it broke <code>logger-colors</code> which were expecting an <code>Integer</code> and map was returning an <code>Array</code>.

<pre><code>class MultiIO
 def self.delegate_all
 IO.methods.each do |m|
 define_method(m) do |*args|
 ret = nil
 @targets.each { |t| ret = t.send(m, *args) }
 ret
 end
 end
 end

 def initialize(*targets)
 @targets = targets
 MultiIO.delegate_all
 end
end
</code></pre>

This will redelegate every method to all targets, and return only the return value of the last call.

Also, if you want colors, STDOUT or STDERR must be put last, since it's the only two were colors are supposed to be output. But then, it will also output colors to your file.

<pre><code>logger = Logger.new MultiIO.new(File.open("log/test.log", 'w'), STDOUT)
logger.error "Roses are red"
logger.unknown "Violets are blue"
</code></pre>

blocks|key|863028|text|我已经编写了一个小RubyGem，它允许您执行以下几项操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|863029|#+Pipe+calls+to+an+instance+of+Ruby's+logger+class+to+$stdout
require+'teerb'

log_file+=+File.open("debug.log",+"a")
logger+=+Logger.new(TeeRb::IODelegate.new(log_file,+STDOUT))

logger.warn+"warn"
$stderr.puts+"stderr+hello"
puts+"stdout+hello"|code-block|syntax|javascript|863030|你可以在github上找到代码：teerb|offset|length|863031|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/phuesler/teerb^0|0|0|G|5|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

I have written a little RubyGem that allows you to do several of these things:

<pre><code># Pipe calls to an instance of Ruby's logger class to $stdout
require 'teerb'

log_file = File.open("debug.log", "a")
logger = Logger.new(TeeRb::IODelegate.new(log_file, STDOUT))

logger.warn "warn"
$stderr.puts "stderr hello"
puts "stdout hello"
</code></pre>

You can find the code on github: <a href="https://github.com/phuesler/teerb" rel="nofollow">teerb</a>

blocks|key|863109|text|我认为您的STDOUT用于关键的运行时信息和引发的错误。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|863110|所以我使用|863111|++$log+=+Logger.new('process.log',+'daily')|code-block|syntax|javascript|863112|来记录调试和常规日志，然后写了几个|863113|++puts+"doing+stuff..."|863114|在那里我需要看到我的脚本正在运行的STDOUT信息！|863115|只是我的10分钱:-)|863116|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

I think your STDOUT is used for critical runtime info and errors raised.

So I use

<pre><code> $log = Logger.new('process.log', 'daily')
</code></pre>

to log debug and regular logging, and then wrote a few

<pre><code> puts "doing stuff..."
</code></pre>

where I need to see STDOUT information that my scripts were running at all!

Bah, just my 10 cents :-)

blocks|key|863142|text|如果您使用的是Rails+3或4，就像this+blog+post指出的那样，使用Rails+4+has+this+functionality+built+in。所以你可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|863143|#+config/environment/production.rb
file_logger+=+Logger.new(Rails.root.join("log/alternative-output.log"))
config.logger.extend(ActiveSupport::Logger.broadcast(file_logger))|code-block|syntax|javascript|863144|或者，如果你使用的是Rails+3，你可以向后移植它：|863145|#+config/initializers/alternative_output_log.rb

#+backported+from+rails4
module+ActiveSupport
++class+Logger+<+::Logger
++++#+Broadcasts+logs+to+multiple+loggers.+Returns+a+module+to+be
++++#+`extended`'ed+into+other+logger+instances.
++++def+self.broadcast(logger)
++++++Module.new+do
++++++++define_method(:add)+do+%7C*args,+&block%7C
++++++++++logger.add(*args,+&block)
++++++++++super(*args,+&block)
++++++++end

++++++++define_method(:<<)+do+%7Cx%7C
++++++++++logger+<<+x
++++++++++super(x)
++++++++end

++++++++define_method(:close)+do
++++++++++logger.close
++++++++++super()
++++++++end

++++++++define_method(:progname=)+do+%7Cname%7C
++++++++++logger.progname+=+name
++++++++++super(name)
++++++++end

++++++++define_method(:formatter=)+do+%7Cformatter%7C
++++++++++logger.formatter+=+formatter
++++++++++super(formatter)
++++++++end

++++++++define_method(:level=)+do+%7Clevel%7C
++++++++++logger.level+=+level
++++++++++super(level)
++++++++end
++++++end
++++end
++end
end

file_logger+=+Logger.new(Rails.root.join("log/alternative-output.log"))
Rails.logger.extend(ActiveSupport::Logger.broadcast(file_logger))|863146|entityMap|0|LINK|mutability|MUTABLE|url|http://railsware.com/blog/2014/08/07/rails-logging-into-several-backends/|1|https://github.com/rails/rails/blob/v4.0.0/activesupport/lib/active_support/logger.rb^0|J|E|0|15|13|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]|$A|10|B|11|1|12]]|C|$]]|$1|D|3|E|5|F|7|13|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|14|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|15|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|16|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]]]

If you're in Rails 3 or 4, as <a href="http://railsware.com/blog/2014/08/07/rails-logging-into-several-backends/">this blog post</a> points out, <a href="https://github.com/rails/rails/blob/v4.0.0/activesupport/lib/active_support/logger.rb">Rails 4 has this functionality built in</a>. So you can do:

<pre><code># config/environment/production.rb
file_logger = Logger.new(Rails.root.join("log/alternative-output.log"))
config.logger.extend(ActiveSupport::Logger.broadcast(file_logger))
</code></pre>

Or if you're on Rails 3, you can backport it:

<pre><code># config/initializers/alternative_output_log.rb

# backported from rails4
module ActiveSupport
 class Logger &lt; ::Logger
 # Broadcasts logs to multiple loggers. Returns a module to be
 # `extended`'ed into other logger instances.
 def self.broadcast(logger)
 Module.new do
 define_method(:add) do |*args, &amp;block|
 logger.add(*args, &amp;block)
 super(*args, &amp;block)
 end

 define_method(:&lt;&lt;) do |x|
 logger &lt;&lt; x
 super(x)
 end

 define_method(:close) do
 logger.close
 super()
 end

 define_method(:progname=) do |name|
 logger.progname = name
 super(name)
 end

 define_method(:formatter=) do |formatter|
 logger.formatter = formatter
 super(formatter)
 end

 define_method(:level=) do |level|
 logger.level = level
 super(level)
 end
 end
 end
 end
end

file_logger = Logger.new(Rails.root.join("log/alternative-output.log"))
Rails.logger.extend(ActiveSupport::Logger.broadcast(file_logger))
</code></pre>

blocks|key|863216|text|还有一种方法。如果您正在使用带标记的日志记录，并且还需要在另一个日志文件中使用标记，则可以使用以下方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|863217|#+backported+from+rails4
#+config/initializers/active_support_logger.rb
module+ActiveSupport
+class+Logger+<+::Logger

+#+Broadcasts+logs+to+multiple+loggers.+Returns+a+module+to+be
+#+`extended`'ed+into+other+logger+instances.
+def+self.broadcast(logger)
++Module.new+do
++++define_method(:add)+do+%7C*args,+&block%7C
++++++logger.add(*args,+&block)
++++++super(*args,+&block)
++++end

++++define_method(:<<)+do+%7Cx%7C
++++++logger+<<+x
++++++super(x)
++++end

++++define_method(:close)+do
++++++logger.close
++++++super()
++++end

++++define_method(:progname=)+do+%7Cname%7C
++++++logger.progname+=+name
++++++super(name)
++++end

++++define_method(:formatter=)+do+%7Cformatter%7C
++++++logger.formatter+=+formatter
++++++super(formatter)
++++end

++++define_method(:level=)+do+%7Clevel%7C
++++++logger.level+=+level
++++++super(level)
++++end

+++end+#+Module.new
+end+#+broadcast

+def+initialize(*args)
+++super
+++@formatter+=+SimpleFormatter.new
+end

++#+Simple+formatter+which+only+displays+the+message.
++class+SimpleFormatter+<+::Logger::Formatter
+++#+This+method+is+invoked+when+a+log+event+occurs
+++def+call(severity,+time,+progname,+msg)
+++element+=+caller[4]+?+caller[4].split("/").last+:+"UNDEFINED"
++++"#{Thread.current[:activesupport_tagged_logging_tags]%7C%7Cnil+}+#+{time.to_s(:db)}+#{severity}+#{element}+--+#{String+===+msg+?+msg+:+msg.inspect}\n"
+++end
++end

+end+#+class+Logger
end+#+module+ActiveSupport

custom_logger+=+ActiveSupport::Logger.new(Rails.root.join("log/alternative_#{Rails.env}.log"))
Rails.logger.extend(ActiveSupport::Logger.broadcast(custom_logger))|code-block|syntax|javascript|863218|在此之后，您将在备用记录器中获得uuid标签|863219|["fbfea87d1d8cc101a4ff9d12461ae810"]+2015-03-12+16:54:04+INFO+logger.rb:28:in+`call_app'+--+
["fbfea87d1d8cc101a4ff9d12461ae810"]+2015-03-12+16:54:04+INFO+++logger.rb:31:in+`call_app'+--+Started+POST+"/psp/entrypoint"+for+192.168.56.1+at+2015-03-12+16:54:04+%2B0700|863220|希望这能帮助到一些人。|863221|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

One more way.
If you're using tagged logging and need tags in another logfile as well, you could do it in this way

<pre><code># backported from rails4
# config/initializers/active_support_logger.rb
module ActiveSupport
 class Logger &lt; ::Logger

 # Broadcasts logs to multiple loggers. Returns a module to be
 # `extended`'ed into other logger instances.
 def self.broadcast(logger)
 Module.new do
 define_method(:add) do |*args, &amp;block|
 logger.add(*args, &amp;block)
 super(*args, &amp;block)
 end

 define_method(:&lt;&lt;) do |x|
 logger &lt;&lt; x
 super(x)
 end

 define_method(:close) do
 logger.close
 super()
 end

 define_method(:progname=) do |name|
 logger.progname = name
 super(name)
 end

 define_method(:formatter=) do |formatter|
 logger.formatter = formatter
 super(formatter)
 end

 define_method(:level=) do |level|
 logger.level = level
 super(level)
 end

 end # Module.new
 end # broadcast

 def initialize(*args)
 super
 @formatter = SimpleFormatter.new
 end

 # Simple formatter which only displays the message.
 class SimpleFormatter &lt; ::Logger::Formatter
 # This method is invoked when a log event occurs
 def call(severity, time, progname, msg)
 element = caller[4] ? caller[4].split("/").last : "UNDEFINED"
 "#{Thread.current[:activesupport_tagged_logging_tags]||nil } # {time.to_s(:db)} #{severity} #{element} -- #{String === msg ? msg : msg.inspect}\n"
 end
 end

 end # class Logger
end # module ActiveSupport

custom_logger = ActiveSupport::Logger.new(Rails.root.join("log/alternative_#{Rails.env}.log"))
Rails.logger.extend(ActiveSupport::Logger.broadcast(custom_logger))
</code></pre>

After this you'll get uuid tags in alternative logger

<pre><code>["fbfea87d1d8cc101a4ff9d12461ae810"] 2015-03-12 16:54:04 INFO logger.rb:28:in `call_app' -- 
["fbfea87d1d8cc101a4ff9d12461ae810"] 2015-03-12 16:54:04 INFO logger.rb:31:in `call_app' -- Started POST "/psp/entrypoint" for 192.168.56.1 at 2015-03-12 16:54:04 +0700
</code></pre>

Hope that helps someone.

blocks|key|646045|text|对于那些喜欢简单的人：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|646046|log+=+Logger.new("%7C+tee+test.log")+#+note+the+pipe+(+'%7C'+)
log.info+"hi"+#+will+log+to+both+STDOUT+and+test.log|code-block|syntax|javascript|646047|source|offset|length|646048|或在记录器格式化程序中打印消息：|646049|log+=+Logger.new("test.log")
log.formatter+=+proc+do+%7Cseverity,+datetime,+progname,+msg%7C
++++puts+msg
++++msg
end
log.info+"hi"+#+will+log+to+both+STDOUT+and+test.log|646050|我实际上正在使用这种技术打印到日志文件，一个云日志服务(日志条目)，如果它是开发环境-也打印到STDOUT。|646051|entityMap|0|LINK|mutability|MUTABLE|url|https://coderwall.com/p/y_b3ra/log-to-stdout-and-a-file-at-the-same-time^0|0|0|0|6|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@]|9|@$I|11|J|12|1|13]]|A|$]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|15|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|16|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

For those who like it simple:

<pre><code>log = Logger.new("| tee test.log") # note the pipe ( '|' )
log.info "hi" # will log to both STDOUT and test.log
</code></pre>

<a href="https://coderwall.com/p/y_b3ra/log-to-stdout-and-a-file-at-the-same-time" rel="noreferrer">source</a>

Or print the message in the Logger formatter:

<pre><code>log = Logger.new("test.log")
log.formatter = proc do |severity, datetime, progname, msg|
 puts msg
 msg
end
log.info "hi" # will log to both STDOUT and test.log
</code></pre>

I'm actually using this technique to print to a log file, a cloud logger service (logentries) and if it's dev environment - also print to STDOUT.

blocks|key|863353|text|您是否仅限于使用标准记录器？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|863354|如果没有，您可以使用log4r|offset|length|863355|require+'log4r'+

LOGGER+=+Log4r::Logger.new('mylog')
LOGGER.outputters+<<+Log4r::StdoutOutputter.new('stdout')
LOGGER.outputters+<<+Log4r::FileOutputter.new('file',+:filename+=>+'test.log')+#attach+to+existing+log-file

LOGGER.info('aa')+#Writs+on+STDOUT+and+sends+to+file|code-block|syntax|javascript|863356|一个优点是:您还可以为stdout和file定义不同的日志级别。|863357|entityMap|0|LINK|mutability|MUTABLE|url|https://rubygems.org/gems/log4r^0|0|A|5|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@$D|W|E|X|1|Y]]|A|$]]|$1|F|3|G|5|H|7|Z|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|10|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

Are you restricted to the standard logger?

If not you may use <a href="https://rubygems.org/gems/log4r" rel="nofollow">log4r</a>:

<pre><code>require 'log4r' 

LOGGER = Log4r::Logger.new('mylog')
LOGGER.outputters &lt;&lt; Log4r::StdoutOutputter.new('stdout')
LOGGER.outputters &lt;&lt; Log4r::FileOutputter.new('file', :filename =&gt; 'test.log') #attach to existing log-file

LOGGER.info('aa') #Writs on STDOUT and sends to file
</code></pre>

One advantage: You could also define different log-levels for stdout and file.

blocks|key|863421|text|@jonas054上面的答案很好，但它会在每个新的委托中污染MultiDelegator类。如果您多次使用MultiDelegator，它将不断向类添加方法，这是不可取的。(如下图所示)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|863422|这里是相同的实现，但是使用了匿名类，这样方法就不会污染委派类。|863423|class+BetterMultiDelegator

++def+self.delegate(*methods)
++++Class.new+do
++++++def+initialize(*targets)
++++++++@targets+=+targets
++++++end

++++++methods.each+do+%7Cm%7C
++++++++define_method(m)+do+%7C*args%7C
++++++++++@targets.map+{+%7Ct%7C+t.send(m,+*args)+}
++++++++end
++++++end

++++++class+<<self
++++++++alias+to+new
++++++end
++++end+#+new+class
++end+#+delegate

end|code-block|syntax|javascript|863424|以下是原始实现与修改后的实现对比的方法污染示例：|863425|tee+=+MultiDelegator.delegate(:write).to(STDOUT)
tee.respond_to?+:write
#+=>+true
tee.respond_to?+:size
#+=>+false+|863426|上面的一切都很好。tee有一个write方法，但没有预期的size方法。现在，考虑一下当我们创建另一个代理时：|863427|tee2+=+MultiDelegator.delegate(:size).to("bar")
tee2.respond_to?+:size
#+=>+true
tee2.respond_to?+:write
#+=>+true+++!!!!!+Bad
tee.respond_to?+:size
#+=>+true+++!!!!!+Bad|863428|哦，不，tee2像预期的那样响应size，但由于第一个委托，它也响应write。由于方法污染，甚至tee现在也对size做出了响应。|863429|与匿名类解决方案相比，一切都如预期的那样：|863430|see+=+BetterMultiDelegator.delegate(:write).to(STDOUT)
see.respond_to?+:write
#+=>+true
see.respond_to?+:size
#+=>+false

see2+=+BetterMultiDelegator.delegate(:size).to("bar")
see2.respond_to?+:size
#+=>+true
see2.respond_to?+:write
#+=>+false
see.respond_to?+:size
#+=>+false|863431|entityMap^0|U|E|1H|E|0|0|0|0|0|9|3|F|5|T|4|0|0|4|4|G|4|Y|5|1D|3|1K|4|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|17|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|18|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|19|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|1A|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|1B|8|@$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]|$9|1G|A|1H|B|C]]|D|@]|E|$]]|$1|S|3|T|5|J|7|1I|8|@]|D|@]|E|$K|L]]|$1|U|3|V|5|6|7|1J|8|@$9|1K|A|1L|B|C]|$9|1M|A|1N|B|C]|$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]|$9|1S|A|1T|B|C]]|D|@]|E|$]]|$1|W|3|X|5|6|7|1U|8|@]|D|@]|E|$]]|$1|Y|3|Z|5|J|7|1V|8|@]|D|@]|E|$K|L]]|$1|10|3|-4|5|6|7|1W|8|@]|D|@]|E|$]]]|11|$]]

@jonas054's answer above is great, but it pollutes the <code>MultiDelegator</code> class with every new delegate. If you use <code>MultiDelegator</code> several times, it will keep adding methods to the class, which is undesirable. (See bellow for example)

Here is the same implementation, but using anonymous classes so the methods don't pollute the delegator class.

<pre><code>class BetterMultiDelegator

 def self.delegate(*methods)
 Class.new do
 def initialize(*targets)
 @targets = targets
 end

 methods.each do |m|
 define_method(m) do |*args|
 @targets.map { |t| t.send(m, *args) }
 end
 end

 class &lt;&lt;self
 alias to new
 end
 end # new class
 end # delegate

end
</code></pre>

Here is an example of the method pollution with the original implementation, contrasted with the modified implementation:

<pre><code>tee = MultiDelegator.delegate(:write).to(STDOUT)
tee.respond_to? :write
# =&gt; true
tee.respond_to? :size
# =&gt; false 
</code></pre>

All is good above. <code>tee</code> has a <code>write</code> method, but no <code>size</code> method as expected. Now, consider when we create another delegate:

<pre><code>tee2 = MultiDelegator.delegate(:size).to("bar")
tee2.respond_to? :size
# =&gt; true
tee2.respond_to? :write
# =&gt; true !!!!! Bad
tee.respond_to? :size
# =&gt; true !!!!! Bad
</code></pre>

Oh no, <code>tee2</code> responds to <code>size</code> as expected, but it also responds to <code>write</code> because of the first delegate. Even <code>tee</code> now responds to <code>size</code> because of the method pollution. 

Contrast this to the anonymous class solution, everything is as expected:

<pre><code>see = BetterMultiDelegator.delegate(:write).to(STDOUT)
see.respond_to? :write
# =&gt; true
see.respond_to? :size
# =&gt; false

see2 = BetterMultiDelegator.delegate(:size).to("bar")
see2.respond_to? :size
# =&gt; true
see2.respond_to? :write
# =&gt; false
see.respond_to? :size
# =&gt; false
</code></pre>

blocks|key|863462|text|还有一个选项;-)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|863463|require+'logger'

class+MultiDelegator
++def+initialize(*targets)
++++@targets+=+targets
++end

++def+method_missing(method_sym,+*arguments,+&block)
++++@targets.each+do+%7Ctarget%7C
++++++target.send(method_sym,+*arguments,+&block)+if+target.respond_to?(method_sym)
++++end
++end
end

log+=+MultiDelegator.new(Logger.new(STDOUT),+Logger.new(File.open("debug.log",+"a")))

log.info('Hello+...')|code-block|syntax|javascript|863464|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

One more option ;-)

<pre><code>require 'logger'

class MultiDelegator
 def initialize(*targets)
 @targets = targets
 end

 def method_missing(method_sym, *arguments, &amp;block)
 @targets.each do |target|
 target.send(method_sym, *arguments, &amp;block) if target.respond_to?(method_sym)
 end
 end
end

log = MultiDelegator.new(Logger.new(STDOUT), Logger.new(File.open("debug.log", "a")))

log.info('Hello ...')
</code></pre>

blocks|key|863500|text|快速和肮脏(参考：https://coderwall.com/p/y_b3ra/log-to-stdout-and-a-file-at-the-same-time)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|863501|require+'logger'
ll=Logger.new('%7C+tee+script.log')
ll.info('test')|code-block|syntax|javascript|863502|entityMap|0|LINK|mutability|MUTABLE|url|https://coderwall.com/p/y_b3ra/log-to-stdout-and-a-file-at-the-same-time^0|9|20|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Quick and dirty (ref: <a href="https://coderwall.com/p/y_b3ra/log-to-stdout-and-a-file-at-the-same-time" rel="nofollow noreferrer">https://coderwall.com/p/y_b3ra/log-to-stdout-and-a-file-at-the-same-time</a>)

<pre><code>require 'logger'
ll=Logger.new('| tee script.log')
ll.info('test')
</code></pre>

blocks|key|863535|text|这是@rado解决方案的简化。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|863536|def+delegator(*methods)
++Class.new+do
++++def+initialize(*targets)
++++++@targets+=+targets
++++end

++++methods.each+do+%7Cm%7C
++++++define_method(m)+do+%7C*args%7C
++++++++@targets.map+{+%7Ct%7C+t.send(m,+*args)+}
++++++end
++++end

++++class+<<+self
++++++alias+for+new
++++end
++end+#+new+class
end+#+delegate|code-block|syntax|javascript|863537|它具有与他相同的优点，而不需要外部类包装器。在单独的ruby文件中有一个有用的实用程序。|863538|使用它作为一行程序来生成委托实例，如下所示：|863539|IO_delegator_instance+=+delegator(:write,+:read).for(STDOUT,+STDERR)
IO_delegator_instance.write("blah")|863540|或者将其用作工厂，如下所示：|863541|logger_delegator_class+=+delegator(:log,+:warn,+:error)
secret_delegator+=+logger_delegator_class(main_logger,+secret_logger)
secret_delegator.warn("secret")

general_delegator+=+logger_delegator_class(main_logger,+debug_logger,+other_logger)+
general_delegator.log("message")|863542|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|W|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

This is a simplification of @rado's solution.

<pre><code>def delegator(*methods)
 Class.new do
 def initialize(*targets)
 @targets = targets
 end

 methods.each do |m|
 define_method(m) do |*args|
 @targets.map { |t| t.send(m, *args) }
 end
 end

 class &lt;&lt; self
 alias for new
 end
 end # new class
end # delegate
</code></pre>

It has all the same benefits as his without the need of the outer class wrapper. Its a useful utility to have in a separate ruby file.

Use it as a one-liner to generate delegator instances like so:

<pre><code>IO_delegator_instance = delegator(:write, :read).for(STDOUT, STDERR)
IO_delegator_instance.write("blah")
</code></pre>

OR use it as a factory like so:

<pre><code>logger_delegator_class = delegator(:log, :warn, :error)
secret_delegator = logger_delegator_class(main_logger, secret_logger)
secret_delegator.warn("secret")

general_delegator = logger_delegator_class(main_logger, debug_logger, other_logger) 
general_delegator.log("message")
</code></pre>

blocks|key|863584|text|您可以使用loog+gem中的Loog::Tee对象：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|863585|require+'loog'
logger+=+Loog::Tee.new(first,+second)|code-block|syntax|javascript|863586|这正是你要找的。|863587|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/yegor256/loog^0|5|4|F|9|5|4|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|F|3|G|5|H|7|12|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|13|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

You can use <code>Loog::Tee</code> object from <a href="https://github.com/yegor256/loog" rel="nofollow noreferrer"><code>loog</code></a> gem:

<pre class="lang-rb prettyprint-override"><code>require 'loog'
logger = Loog::Tee.new(first, second)
</code></pre>

Exactly what you are looking for.

blocks|key|646375|text|我最近也有这样的需求，所以我实现了一个库来做这件事。我刚刚发现了这个StackOverflow问题，所以我把它发布给任何需要它的人：https://github.com/agis/multi_io。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|646376|与这里提到的其他解决方案相比，它努力成为自己的IO对象，因此可以作为其他常规IO对象(文件、套接字等)的替代。|style|CODE|646377|也就是说，我还没有实现所有的标准IO方法，但是那些遵循IO语义的方法(例如，#write返回写入所有底层IO目标的字节数之和)。|646378|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/agis/multi_io^0|1U|W|0|0|N|2|0|12|6|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@$A|S|B|T|1|U]]|C|$]]|$1|D|3|E|5|6|7|V|8|@$A|W|B|X|F|G]]|9|@]|C|$]]|$1|H|3|I|5|6|7|Y|8|@$A|Z|B|10|F|G]]|9|@]|C|$]]|$1|J|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|K|$L|$5|M|N|O|C|$P|Q]]]]

I also has this need recently so I implemented a library that does this. I just discovered this StackOverflow question, so I'm putting it out there for anyone that needs it: <a href="https://github.com/agis/multi_io" rel="nofollow noreferrer">https://github.com/agis/multi_io</a>.

Compared to the other solutions mentioned here, this strives to be an <code>IO</code> object of its own, so it can be used as a drop-in replacement for other regular IO objects (files, sockets etc.)

That said, I've not yet implemented all the standard IO methods, but those that are, follow the IO semantics (e.g. for example, <code>#write</code> returns the sum of the number of bytes written to all the underlying IO targets).

blocks|key|863684|text|您可以继承Logger并覆盖write方法：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|863685|class+LoggerWithStdout+<+Logger
++def+initialize(*)
++++super

++++def+@logdev.write(msg)
++++++super

++++++puts+msg
++++end
++end
end

logger+=+LoggerWithStdout.new('path/to/log_file.log')|code-block|syntax|javascript|863686|entityMap^0|5|6|E|5|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

You can inherit <code>Logger</code> and override the <code>write</code> method:
<pre><code>class LoggerWithStdout &lt; Logger
 def initialize(*)
 super

 def @logdev.write(msg)
 super

 puts msg
 end
 end
end

logger = LoggerWithStdout.new('path/to/log_file.log')
</code></pre>

Someting like a tee functionality in logger.

问如何让ruby logger日志输出到stdout以及文件？
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问如何让ruby logger日志输出到stdout以及文件？
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