What does bundle exec rake mean

Question

What does bundle exec rake db migrate mean  Or just bundle exec rake  lt command gt  in general   I understand that bundle takes care of maintaining things in the Gemfile   I know what the word  exec  means   I understand that rake maintains all the different scripty things you can do  and I know that db migrate is one of those  I just don t know what all these words are doing together   Why should bundle be used to execute rake to execute a database migrate

User · Answer

This comes up a lot when your gemfile lock has different versions of the gems installed on your machine  You may get a warning after running rake  or rspec or others  such as    You have already activated rake 10 3 1  but your Gemfile requires rake 10 1 0  Prepending  bundle exec  to your command may solve this   Prepending bundle exec tells the bundler to execute this command regardless of the version differential  There isn t always an issue  however  you might run into problems   Fortunately  there is a gem that solves this  rubygems-bundler      gem install rubygems-bundler     gem regenerate binstubs  Then try your rake  rspec  or whatever again

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I have not used bundle exec much  but am setting it up now     I have had instances where the wrong rake was used and much time wasted tracking down the problem  This helps you avoid that   Here s how to set up RVM so you can use bundle exec by default within a specific project directory   https   thoughtbot com blog use-bundlers-binstubs

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bundle exec is a Bundler command to execute a script in the context of the current bundle  the one from your directory s Gemfile   rake db migrate is the script where db is the namespace and migrate is the task name defined   So bundle exec rake db migrate executes the rake script with the command db migrate in the context of the current bundle   As to the  why   I ll quote from the bundler page       In some cases  running executables without bundle exec may work  if the executable happens to be installed in your system and does not pull in any gems that conflict with your bundle       However  this is unreliable and is the source of considerable pain  Even if it looks like it works  it may not work in the future or on another machine

User · Answer

You re running bundle exec on a program  The program s creators wrote it when certain versions of gems were available  The program Gemfile specifies the versions of the gems the creators decided to use  That is  the script was made to run correctly against these gem versions    Your system-wide Gemfile may differ from this Gemfile  You may have newer or older gems with which this script doesn t play nice  This difference in versions can give you weird errors   bundle exec helps you avoid these errors  It executes the script using the gems specified in the script s Gemfile rather than the systemwide Gemfile  It executes the certain gem versions with the magic of shell aliases   See more on the man page   Here s an example Gemfile   source  http   rubygems org   gem  rails    2 8 3    Here  bundle exec would execute the script using rails version 2 8 3 and not some other version you may have installed system-wide

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It should probably be mentioned  that there are ways to omit bundle exec  they are all stated in chapter 3 6 1 of Michael Hartls Ruby on Rails Tutorial book     The simplest is to just use a sufficiently up-to-date version of RVM     1 11 x     If you re restricted to an earlier version of RVM  you can always use this method also mentioned by calasyr     rvm get head  amp  amp  rvm reload   chmod  x  rvm path hooks after cd bundler   bundle install --binstubs   bundler stubs   The bundler stubs directory should then also be added to the  gitignore file   A third option is to use the rubygems-bundler gem if you re not using RVM     gem install rubygems-bundler   gem regenerate binstubs

User · Answer

It means use rake that bundler is aware of and is part of your Gemfile over any rake that bundler is not aware of and run the db migrate task

User · Answer

When you directly run the rake task or execute any binary file of a gem  there is no guarantee that the command will behave as expected  Because it might happen that you already have the same gem installed on your system which have a version say 1 0 but in your project you have higher version say 2 0  In this case you can not predict which one will be used   To enforce the desired gem version you take the help of bundle exec command which would execute the binary in context of current bundle  That means when you use bundle exec  bundler checks the gem version configured for the current project and use that to perform the task   I have also written a post about it which also shows how we can avoid using it using bin stubs

[ruby-on-rails] What does bundle exec rake mean?

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