utmp log file, Linux/glibc version: Ruby parsing library

KS implementation details

License: CC0-1.0

References

This page hosts a formal specification of utmp log file, Linux/glibc version using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime library

All parsing code for Ruby generated by Kaitai Struct depends on the Ruby runtime library. You have to install it before you can parse data.

The Ruby runtime library can be installed from RubyGems:

gem install kaitai-struct

Code

Parse a local file and get structure in memory:

data = GlibcUtmp.from_file("path/to/local/file.bin")

Or parse structure from a string of bytes:

bytes = "\x00\x01\x02..."
data = GlibcUtmp.new(Kaitai::Struct::Stream.new(bytes))

After that, one can get various attributes from the structure by invoking getter methods like:

data.records # => get records

Ruby source code to parse utmp log file, Linux/glibc version

glibc_utmp.rb

Download 

# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

require 'kaitai/struct/struct'

unless Gem::Version.new(Kaitai::Struct::VERSION) >= Gem::Version.new('0.9')
  raise "Incompatible Kaitai Struct Ruby API: 0.9 or later is required, but you have #{Kaitai::Struct::VERSION}"
end

class GlibcUtmp < Kaitai::Struct::Struct

  ENTRY_TYPE = {
    0 => :entry_type_empty,
    1 => :entry_type_run_lvl,
    2 => :entry_type_boot_time,
    3 => :entry_type_new_time,
    4 => :entry_type_old_time,
    5 => :entry_type_init_process,
    6 => :entry_type_login_process,
    7 => :entry_type_user_process,
    8 => :entry_type_dead_process,
    9 => :entry_type_accounting,
  }
  I__ENTRY_TYPE = ENTRY_TYPE.invert
  def initialize(_io, _parent = nil, _root = self)
    super(_io, _parent, _root)
    _read
  end

  def _read
    @_raw_records = []
    @records = []
    i = 0
    while not @_io.eof?
      @_raw_records << @_io.read_bytes(384)
      _io__raw_records = Kaitai::Struct::Stream.new(@_raw_records.last)
      @records << Record.new(_io__raw_records, self, @_root)
      i += 1
    end
    self
  end
  class Record < Kaitai::Struct::Struct
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @ut_type = Kaitai::Struct::Stream::resolve_enum(GlibcUtmp::ENTRY_TYPE, @_io.read_s4le)
      @pid = @_io.read_u4le
      @line = (@_io.read_bytes(32)).force_encoding("UTF-8")
      @id = (@_io.read_bytes(4)).force_encoding("UTF-8")
      @user = (@_io.read_bytes(32)).force_encoding("UTF-8")
      @host = (@_io.read_bytes(256)).force_encoding("UTF-8")
      @exit = @_io.read_u4le
      @session = @_io.read_s4le
      @tv = Timeval.new(@_io, self, @_root)
      @addr_v6 = @_io.read_bytes(16)
      @reserved = @_io.read_bytes(20)
      self
    end

    ##
    # Type of login
    attr_reader :ut_type

    ##
    # Process ID of login process
    attr_reader :pid

    ##
    # Devicename
    attr_reader :line

    ##
    # Inittab ID
    attr_reader :id

    ##
    # Username
    attr_reader :user

    ##
    # Hostname for remote login
    attr_reader :host

    ##
    # Exit status of a process marked as DEAD_PROCESS
    attr_reader :exit

    ##
    # Session ID, used for windowing
    attr_reader :session

    ##
    # Time entry was made
    attr_reader :tv

    ##
    # Internet address of remote host
    attr_reader :addr_v6
    attr_reader :reserved
  end
  class Timeval < Kaitai::Struct::Struct
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @sec = @_io.read_s4le
      @usec = @_io.read_s4le
      self
    end

    ##
    # Seconds
    attr_reader :sec

    ##
    # Microseconds
    attr_reader :usec
  end
  attr_reader :records
  attr_reader :_raw_records
end