Class: IO::Tail::Logfile

Inherits:
File show all
Defined in:
lib/io/tail/logfile.rb

Overview

This is an easy to use Logfile class that includes the File::Tail module.

Usage

The unix command “tail -10f filename” can be emulated like that:

File::Tail::Logfile.open(filename, :backward => 10) do |log|
  log.tail { |line| puts line }
end

Or a bit shorter:

File::Tail::Logfile.tail(filename, :backward => 10) do |line|
  puts line
end

To skip the first 10 lines of the file do that:

File::Tail::Logfile.open(filename, :forward => 10) do |log|
  log.tail { |line| puts line }
end

The unix command “head -10 filename” can be emulated like that:

File::Tail::Logfile.open(filename, :return_if_eof => true) do |log|
  log.tail(10) { |line| puts line }
end

Instance Attribute Summary

Attributes inherited from File

#_file

Attributes inherited from Tailable

#break_if_eof, #default_bufsize, #interval, #max_interval, #reopen_deleted, #reopen_suspicious, #return_if_eof, #suspicious_interval

Class Method Summary collapse

Methods inherited from File

#backward, #close, #forward, #handle_EOFError, #handle_ReopenException, #initialize, #path, #puts, #readline, #reopen_tailable, #restat

Methods inherited from Tailable

#after_reopen, #close, #tail

Constructor Details

This class inherits a constructor from IO::Tail::File

Class Method Details

.open(filename, opts = {}, &block) ⇒ Object

This method creates an File::Tail::Logfile object and yields to it, and closes it, if a block is given, otherwise it just returns it. The opts hash takes an option like

  • :backward => 10 to go backwards

  • :forward => 10 to go forwards

in the logfile for 10 lines at the start. The buffersize for going backwards can be set with the

  • :bufsiz => 8192 option.

To define a callback, that will be called after a reopening occurs, use:

  • :after_reopen => lambda { |file| p file }

Every attribute of File::Tail can be set with a :attributename => value option.



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# File 'lib/io/tail/logfile.rb', line 41

def self.open(filename, opts = {}, &block) # :yields: file
  file = new filename
  opts.each do |o, v|
    writer = o.to_s + "="
    file.__send__(writer, v) if file.respond_to? writer
  end
  if opts.key?(:wind) or opts.key?(:rewind)
    warn ":wind and :rewind options are deprecated, "\
      "use :forward and :backward instead!"
  end
  if backward = opts[:backward] || opts[:rewind]
    (args = []) << backward
    args << opt[:bufsiz] if opts[:bufsiz]
    file.backward(*args)
  elsif forward = opts[:forward] || opts[:wind]
    file.forward(forward)
  end
  if opts[:after_reopen]
    file.after_reopen(&opts[:after_reopen])
  end
  if block_given?
    begin
      block.call file
    ensure
      file.close
      nil
    end
  else
    file
  end
end

.tail(filename, opts = {}, &block) ⇒ Object

Like open, but yields to every new line encountered in the logfile in block.



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# File 'lib/io/tail/logfile.rb', line 75

def self.tail(filename, opts = {}, &block)
  if ([ :forward, :backward ] & opts.keys).empty?
    opts[:backward] = 0
  end
  open(filename, opts) do |log|
    log.tail { |line| block.call line }
  end
end