Class: OpenVZ::Shell

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

Overview

This code is completely borrowed from marionette-collective.

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.exitcode

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/openvz/shell.rb', line 27

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

    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/openvz/shell.rb', line 25

def command
  @command
end

#cwd ⇒ Object (readonly)

Returns the value of attribute cwd.



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# File 'lib/openvz/shell.rb', line 25

def cwd
  @cwd
end

#environment ⇒ Object (readonly)

Returns the value of attribute environment.



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# File 'lib/openvz/shell.rb', line 25

def environment
  @environment
end

#status ⇒ Object (readonly)

Returns the value of attribute status.



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# File 'lib/openvz/shell.rb', line 25

def status
  @status
end

#stderr ⇒ Object (readonly)

Returns the value of attribute stderr.



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# File 'lib/openvz/shell.rb', line 25

def stderr
  @stderr
end

#stdin ⇒ Object (readonly)

Returns the value of attribute stdin.



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# File 'lib/openvz/shell.rb', line 25

def stdin
  @stdin
end

#stdout ⇒ Object (readonly)

Returns the value of attribute stdout.



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# File 'lib/openvz/shell.rb', line 25

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/openvz/shell.rb', line 65

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