irb | 易学教程

How to kill a scan operation in hbase shell without Ctrl-C

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问题 Sometimes when I run a scan '<tablename> . I see a continuous flood of data being printed because the table is big. I want to kill the process that print the data. Is there a way to do it other than Ctrl-C ? because Ctrl-C kills the shell process and I don't want to exit the shell. 回答1: You could use scan with LIMIT to limit the scan output on shell : scan 'table', LIMIT => 5 This will show you only 5 rows. You could also press ctlr+s to hold the scan, if you have done a full scan and want to

History not saving

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Why is my irb history no longer saving? It turns out that ruby 1.8.7 introduced a bug whereby finalizers are no longer guaranteed to run. To resolve this, I added the following code snippet to my .irbrc file: require 'irb/ext/save-history' Kernel.at_exit do IRB::HistorySavingAbility.create_finalizer.call(IRB.CurrentContext.instance_variable_get(:@io).send(:binding)) end I ran into this with ruby 2.3.7 as well. It was caused by rvm ruby package not having the correct permissions to update the default .irbrc_history file. This appears to be a known bug . An easy work around is to just change the

irb loading wrong ruby and gem path, using rbenv

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I started using rbenv for ruby version management and I'm finding that irb not loading the correct ruby version and gem version. Here are the details. irb Gem.path says: `>> Gem.path => ["/Users/Air/.gem/ruby/1.8", "/Library/Ruby/Gems/1.8", "/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8"]` Now in irb if I type: puts $: `>> puts $: /Library/Ruby/Site/1.8 /Library/Ruby/Site/1.8/powerpc-darwin11.0 /Library/Ruby/Site/1.8/universal-darwin11.0 /Library/Ruby/Site /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/vendor_ruby/1.8 /System/Library

Get all local variables or available methods from irb?

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问题 When I go into irb and type in a command that does not exist I get an error stating "undefined local variable or method 'my_method' for main:Object (NameError)" Is there a way to just get a list of what local variables or methods ARE available? This would be really useful for exploring ruby. 回答1: Look for methods in the Kernel, Object and Module : e.g. local_variables, instance_methods, instance_variables. Other great methods in there. inspect is another one. 回答2: Great answers. As you

Rails console - use image_tag method

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问题 How can I execute a image_tag method in a Rails console Run the console $ rails c Load helpers include ActionView::Helpers Execute the command image_tag('test.png') I got a strange error. Please help! 回答1: Not sure why you're getting that error. It is strange. But the Rails Console exposes the helper methods through the helper variable. So this should work: helper.image_tag('test.png') 回答2: OK... I found the solution. The error is showing only in Rails 3 but I fixed it by setting the config

How can I pass <arguments> to IRB if I don't specify <programfile>?

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问题 Since: irb --help Usage: irb.rb [options] [programfile] [arguments] I know I can pass arguments to ARGV if I include a programfile eg: irb test.rb A B C where test.irb is simply "p ARGV" produces: ["a", "b", "c"] Making programfile be con in DOS... I can do following irb con A B C con(main):001:0> ARGV produces: ARGV => ["A", "B", "C"] but this is system dependent and has the side effect of echoing input :-( What i really like is something like irb -- a b c BTW: I know I can set ARGV inside

Rails: How to cancel current statements in rails console?

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I'm using Rails 2.3.8 with jRuby for a project. and I regularly use rails console for testing my classes and API, where somehow I experience one problem. when I am working in the Rails console, if I mistakenly input some multi-line commands, is there a way to cancel it somewhere in the middle? e.g.: >> [1,2,3,4].inject(1){ ?> All I found is it will be expecting me to finish the whole completed statement, but all I wanna do is to cancel all current statements. I've tried Ctrl+C, but it didn't work for me. Any advice would be very much appreciated. Anil At the prompt, you can use the following

Rails check if IRB console or webpage

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In my model I would like to check if the app is running inside IRB consol or as a website? class MyModel < ActiveRecord::Base def xmethod if !isIRBconsol self.user_id = UserSession.find.user.id end end end This is a bit of a hack, but it should work: class MyModel < ActiveRecord::Base def am_i_in_irb? self.private_methods.include? 'irb_binding' end end But as Kathy Van Stone said above, this is probably something that has a better solution. Why not just if defined?(IRB) ? unless self.private_methods.include? 'irb_binding' #put your rufus scheduling here end 来源： https://stackoverflow.com

Stop rails console from printing out the object at the end of a loop

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问题 If I, say, loop through all the instances of a given model and output something from each, at the end, irb will still print the entire object. If the object ends up taking hundreds of lines, it'll be a long way up before I see what I was actually looking for. Is there a way to disable this in the rails console? 回答1: If you don't want to disable the echo in general you could also call multiple expressions in one command line. Only the last expression's output will be displayed. big_result

Why Active Record relation is not returned in console?

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I have finally started upgrading my Rails apps from 2.3.8 to 3.1.0. I was watching RailsCasts ( http://railscasts.com/episodes/202-active-record-queries-in-rails-3 ) about Active Record queries. When I open up the console (rails c) and do query similar to this: articles = Article.order("name") Instead of returning Active Record relations, I see the query executed. What am I doing wrong here? Rails version: 3.1.0 RVM on 1.9.2 Thank you for your help! EDIT: I have added a screenshot from the example. You're doing everything right. You see query executed because console invokes inspect method on