Wrapper around systemu that handles executing of system commands in a way that makes stdout, stderr and status available. Supports timeouts and sets a default sane environment.

  s = Shell.new("date", opts)
  s.runcommand
  puts s.stdout
  puts s.stderr
  puts s.status.exitstatus

Options hash can have:

  cwd         - the working directory the command will be run from
  stdin       - a string that will be sent to stdin of the program
  stdout      - a variable that will receive stdout, must support <<
  stderr      - a variable that will receive stdin, must support <<
  environment - the shell environment, defaults to include LC_ALL=C
                set to nil to clear the environment even of LC_ALL
  timeout     - a timeout in seconds after which the subprocess is killed,
                the special value :on_thread_exit kills the subprocess
                when the invoking thread (typically the agent) has ended