Class: MCollective::Shell

Inherits:
Object
  • Object
show all
Defined in:
lib/mcollective/shell.rb

Overview

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

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(command, options = {}) ⇒ Shell

Returns a new instance of Shell.



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# File 'lib/mcollective/shell.rb', line 24

def initialize(command, options={})
  @environment = {"LC_ALL" => "C"}
  @command = command
  @status = nil
  @stdout = ""
  @stderr = ""
  @stdin = nil
  @cwd = Dir.tmpdir

  options.each do |opt, val|
    case opt.to_s
      when "stdout"
        raise "stdout should support <<" unless val.respond_to?("<<")
        @stdout = val

      when "stderr"
        raise "stderr should support <<" unless val.respond_to?("<<")
        @stderr = val

      when "stdin"
        raise "stdin should be a String" unless val.is_a?(String)
        @stdin = val

      when "cwd"
        raise "Directory #{val} does not exist" unless File.directory?(val)
        @cwd = val

      when "environment"
        if val.nil?
          @environment = {}
        else
          @environment.merge!(val.dup)
        end
    end
  end
end

Instance Attribute Details

#command ⇒ Object (readonly)

Returns the value of attribute command.



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# File 'lib/mcollective/shell.rb', line 22

def command
  @command
end

#cwd ⇒ Object (readonly)

Returns the value of attribute cwd.



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# File 'lib/mcollective/shell.rb', line 22

def cwd
  @cwd
end

#environment ⇒ Object (readonly)

Returns the value of attribute environment.



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# File 'lib/mcollective/shell.rb', line 22

def environment
  @environment
end

#status ⇒ Object (readonly)

Returns the value of attribute status.



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# File 'lib/mcollective/shell.rb', line 22

def status
  @status
end

#stderr ⇒ Object (readonly)

Returns the value of attribute stderr.



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# File 'lib/mcollective/shell.rb', line 22

def stderr
  @stderr
end

#stdin ⇒ Object (readonly)

Returns the value of attribute stdin.



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# File 'lib/mcollective/shell.rb', line 22

def stdin
  @stdin
end

#stdout ⇒ Object (readonly)

Returns the value of attribute stdout.



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# File 'lib/mcollective/shell.rb', line 22

def stdout
  @stdout
end

Instance Method Details

#runcommand ⇒ Object

Actually does the systemu call passing in the correct environment, stdout and stderr



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# File 'lib/mcollective/shell.rb', line 62

def runcommand
  opts = {"env"    => @environment,
          "stdout" => @stdout,
          "stderr" => @stderr,
          "cwd"    => @cwd}

  opts["stdin"] = @stdin if @stdin

  # Running waitpid on the cid here will start a thread
  # with the waitpid in it, this way even if the thread
  # that started this process gets killed due to agent
  # timeout or such there will still be a waitpid waiting
  # for the child to exit and not leave zombies.
  @status = systemu(@command, opts) do |cid|
    begin
      sleep 1
      Process::waitpid(cid)
    rescue SystemExit
    rescue Errno::ECHILD
    rescue Exception => e
      Log.info("Unexpected exception received while waiting for child process: #{e.class}: #{e}")
    end
  end
end