Question

Full disclosure: I don’t really know Ruby. I’m mostly faking it.

I have a script I want to use to gather inventory in Casper, which I’m using to manage a bunch of Macs. I’m attempting to pass a variable into a shell command with %x. Problem is, Ruby is treating the variable as a comment instead. Here is the relevant code:

def get_host
 host=%x(/usr/sbin/dsconfigad -show | /usr/bin/awk '/Computer Account/ {print $4}').chomp
 raise Error, "this machine must not be bound to AD.\n try again." if host == nil
end

def get_ou
  host = get_host
  dsout = %x(/usr/bin/dscl /Search -read /Computers/#{host}).to_a
  ou = dsout.select {|item| item =~ /OU=/}.to_s.split(",")[1].to_s.gsub(/OU=/, '').chomp
end

I tried using back ticks instead of %x, but got the same result. The command should return a bunch of information about the host it’s run on, but instead it returns the result of dscl /Search -read /Computers, which is always name: dsRecTypeStandard:Computers.

How can I accomplish what I want to do?

Answer 1

The problem is here. The Ruby always returns the last expression in a method.

def get_host
  host=%x(/usr/sbin/dsconfigad -show | /usr/bin/awk '/Computer Account/ {print $4}').chomp
  raise Error, "this machine must not be bound to AD.\n try again." if host == nil
end

In this case, the last expression is:

raise Error, "this machine must not be bound to AD.\n try again." if host == nil

It will return the return value of raise (which don’t gonna happen actually) if host == nil or will return nil if host != nil. So your method will never return something other than nil. Replace it by:

def get_host
  host=%x(/usr/sbin/dsconfigad -show | /usr/bin/awk '/Computer Account/ {print $4}').chomp
  raise Error, "this machine must not be bound to AD.\n try again." if host == nil
  host
end