How to execute commands within Rake tasks?

Question

I have the rake tasks in my rails application. i want to run a commandline commands with in rake task. how can i do this. i tried by the following but fails

desc "Sending the newsletter to all the users"
task :sending_mail do
  run "cd #{RAILS_ROOT} && ar_sendmail -o -t NewsLetters -v"
  system "cd #{RAILS_ROOT} && ar_sendmail -o -t NewsLetters -v &"
end

The above run command throws run method undefined & System command not throwing any errors but not executed.

Solution 1

This links may help you run command line command into ruby ...

http://zhangxh.net/programming/ruby/6-ways-to-run-shell-commands-in-ruby/

Calling shell commands from Ruby

http://blog.jayfields.com/2006/06/ruby-kernel-system-exec-and-x.html

%x[command].each do |f|
  value = f
end

Solution 2

Rake sh built-in task

This is probably the best method:

task(:sh) do
  sh('echo', 'a')
  sh('false')
  sh('echo', 'b')
end

The interface is similar to Kernel.system but:

• it aborts if the return is != 0, so the above never reaches echo b
• the command itself is echoed before the output

Solution 3

run is used by Capistrano and other things for launching commands, but Rake often makes use of Kernel#system instead.

Your command might be being run, but not working. Why not make a wrapper shell script you can test independently, or try and kick off using the full path:

newsletter_script = File.expand_path('ar_sendmail', RAILS_ROOT)

if (File.exist?(newsletter_script))
  unless (system(newsletter_script + ' -o -t NewsLetters -v &'))
    STDERR.puts("Script #{newsletter_script} returned error condition")
  end
else
  STDERR.puts("Could not find newsletter sending script #{newsletter_script}")
end

It would seem odd to have your script not in scripts/

The system call should return true on success. If this is not the case, either the script returned an error code, or the command could't be run.

Comments

[palani]

Hi tadman, Thanks for your answer... i just copied your code and tried but not working as expected..can you please tell me what is File.expand_path do ?

[palani]

Hello tadman, your script looking for the file Rails_Root/ar_sendmailer. but this is not a file and this is command which invoked from Rails app root folder. like [/home/username/railsapp]$ar_sendmail -o -t NewLetter -V . so i rake file i go the Rails application root folder and trigger the above command that what i need... please help me on this

[tadman]

File.expand_path is used to...expand paths, basically. It will properly join two paths together, like appending ar_sendmail on your Rails path, whatever that is. It's also good for eliminating things like ../../ when required, giving you the proper, full path.

[tadman]

You need to know where ar_sendmail is otherwise you won't be able to launch it properly. Your shell has a PATH which can differ from what Ruby will use, and that can make scripts work even when they're not in the directory you're in.

[Florian Loch]

Seems like the best method to me too

[Binary Phile]

Rake has a specific method for running a shell command, #sh. It has the shortcoming of using /bin/sh, not bash however.To use bash from Rake's sh method, see this answer to a duplicate question: stackoverflow.com/questions/9796028/…