This problem is to get into an internship within a devops department:
"Write a ruby library that executes arbitrary system calls (eg: “dmesg", "ping -c 1 www.google.com”) and provides separated output streams of stderr and stdout as well are providing the final return code of the process. Show your work with unit tests.”
Am I supposed to use already established system calls and replicate them in Ruby code? That seems silly to me. Am I supposed to come up with my own arbitrary calls and write a library complete with errors and status calls?
I am not looking for someone to write this for me. I feel that the first step to solving this problem is understanding it.
The assignment is poorly worded, and misuses a number of terms. In addition, we can only guess what they really expect; the appropriate thing to do would be to ask the company directly for clarification.
With that said, what they probably want is a way to process any given command and its arguments as a decorated method, akin to the way Open3#capture3 from the standard library works. That means the code you write should take the command and any arguments as parameters.
For example, using Open3#capture3 from the standard library:
require 'open3'
def command_wrapper cmd, *args
stdout_str, stderr_str, status = Open3.capture3 "#{cmd} #{args.join ' '}"
end
command_wrapper "/bin/echo", "-n", "foo", "bar", "baz"
#=> ["foo bar baz", "", #<Process::Status: pid 31661 exit 0>]
I sincerely doubt that it's useful to re-implement this library, but that certainly seems like what they're asking you to do. Shrug.
You're also supposed to write unit tests for the re-implementation, so you will have to swot something up with a built-in framework like Test::Unit or MiniTest, or an external testing framework like RSpec, or Wrong. See the Ruby Toolbox for a more comprehensive list of available unit testing frameworks.