TailFromSentinel

Parses a file, looking for a sentinel line that satisfies a block, and returns all lines from there until the end of the file (including the sentinel itself).

This can be handy when you are looking for information in a log file only after a certain condition (eg. a date) has been met.

You can either use it on it's own, or subclass it to build your own custom tail-like classes.

Standalone: File.open('/var/log/messages', 'r') do |file| tfs=TailFromSentinel::Base.new(file) { |line| line =~ /Dec 20 11:2d+/ } end tfs.data # => [ 'Dec 20 11:20:00 ...', 'Dec 20 11:21:00 ...', ... ]

Subclassed: class TailMyFile < TailFromSentinel::Base DATA_ROOT="/path/to/data/"

def initialize(data_file)
  file=File.open(File.join(DATA_ROOT, data_file), 'r') do |file|
    super(file, &select_sentinel_criteria(data_file))
  end
end

def select_sentinel_criteria(data_file)
  case data_file
    when ''production.log'
      Proc.new { |line| line =~ /pattern/ }
    when 'development.log'
      Proc.new { |line| line =~ /another pattern/ }
    else
      raise "Unhandled file: #{data_file}"
  end
end

end

t=TailMyFile.new('production.log') t.data # => [ 'Started GET "/pattern ...", " Processing ... ", ... ]