Shells

This gem is a collection of shell classes that can be used to interact with various devices. It started as a secure shell to interact with SSH hosts, then it received a shell to access pfSense devices. A natural progression had me adding a serial shell and another shell to access pfSense devices over serial.

If you can't tell, it was primarily developed to interact with pfSense devices, but also tends to work well for interacting with other devices and hosts as well. With version 0.2, some changes were made to work better with all sorts of shells connections. Version 0.2 is not compatible with code written for version 0.1.

Add this line to your application's Gemfile:

gem 'shells'

And then execute:

$ bundle

Or install it yourself as:

$ gem install shells

Any of the various "Shell" classes can be used to interact with a device or host.

shell = Shells::SshBashShell.new(host: 'my.device.name.or.ip', user: 'somebody', password: 'secret')
shell.run do |sh|
  sh.exec "cd /usr/local/bin"
  user_bin_files = sh.exec("ls -A1").split("\n")
  @app_is_installed = user_bin_files.include?("my_app")
end

If you provide a block to .new, it will be run automatically after initializing the shell.

In most cases you will be sending commands to the shell using the .exec method of the shell passed to the code block. The .exec method returns the output of the command and then you can process the results. You can also request that the .exec method retrieves the exit code from the command as well, but this will only work in some shells.

Shells::SshBashShell.new(host: 'my.device.name.or.ip', user: 'somebody', password: 'secret') do |sh|
  # By default shells do not retrieve exit codes or raise on non-zero exit codes.
  # These parameters can be set in the options list for the constructor as well to change the 
  # default behavior.
  
  # This command will execute the command and then retrieve the exit code.
  # We then perform an action based on the exit code.
  sh.exec "some command", retrieve_exit_code: true
  raise 'Some Error' if sh.last_exit_code != 0
  
  # This command will execute the command then automatically raise an error if the exit code
  # is non-zero.  The error raised is a Shells::NonZeroExitCode exception which happens to have
  # an exit_code property for your rescue code to examine.
  sh.exec "some command", retrieve_exit_code: true, on_non_zero_exit_code: :raise
end

Bug reports and pull requests are welcome on GitHub at https://github.com/barkerest/shells.

The gem is available as open source under the terms of the MIT License.