Class: IO::Tail::File

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

Direct Known Subclasses

Logfile

Instance Attribute Summary collapse

Attributes inherited from Tailable

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

Instance Method Summary collapse

Methods inherited from Tailable

#after_reopen, #tail

Constructor Details

#initialize(file_or_filename = nil) ⇒ File

Returns a new instance of File.



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# File 'lib/io/tail.rb', line 230

def initialize(file_or_filename = nil)
  super()
  if file_or_filename.is_a?(String)
    @_file = ::File.new(file_or_filename, 'rb')
  elsif file_or_filename.is_a?(::File)
    @_file = file_or_filename
  end
  self._file.seek(0, ::File::SEEK_END)
end

Instance Attribute Details

#_file ⇒ Object (readonly)

Returns the value of attribute _file.



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# File 'lib/io/tail.rb', line 228

def _file
  @_file
end

Instance Method Details

#backward(n = 0, bufsize = nil) ⇒ Object

Rewind the last n lines of this file, starting from the end. The default is to start tailing directly from the end of the file.

The additional argument bufsize is used to determine the buffer size that is used to step through the file backwards. It defaults to the block size of the filesystem this file belongs to or 8192 bytes if this cannot be determined.



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# File 'lib/io/tail.rb', line 271

def backward(n = 0, bufsize = nil)
  if n <= 0
    self._file.seek(0, ::File::SEEK_END)
    return self
  end
  bufsize ||= default_bufsize || self._file.stat.blksize || 8192
  size = self._file.stat.size
  begin
    if bufsize < size
      self._file.seek(0, ::File::SEEK_END)
      while n > 0 and self._file.tell > 0 do
        start = self._file.tell
        self._file.seek(-bufsize, ::File::SEEK_CUR)
        buffer = self._file.read(bufsize)
        n -= buffer.count("\n")
        self._file.seek(-bufsize, ::File::SEEK_CUR)
      end
    else
      self._file.seek(0, ::File::SEEK_SET)
      buffer = self._file.read(size)
      n -= buffer.count("\n")
      self._file.seek(0, ::File::SEEK_SET)
    end
  rescue Errno::EINVAL
    size = self._file.tell
    retry
  end
  pos = -1
  while n < 0  # forward if we are too far back
    pos = buffer.index("\n", pos + 1)
    n += 1
  end
  self._file.seek(pos + 1, ::File::SEEK_CUR)
  self
end

#close ⇒ Object 



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# File 'lib/io/tail.rb', line 240

def close
  self._file.close
end

#forward(n = 0) ⇒ Object

Skip the first n lines of this file. The default is to don’t skip any lines at all and start at the beginning of this file.



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# File 'lib/io/tail.rb', line 254

def forward(n = 0)
  self._file.seek(0, ::File::SEEK_SET)
  while n > 0 and not self._file.eof?
    self._file.readline
    n -= 1
  end
  self
end

#handle_EOFError ⇒ Object

On EOF, we seek to position 0 Next read will reopen the file if it has changed



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# File 'lib/io/tail.rb', line 309

def handle_EOFError
  self._file.seek(0, ::File::SEEK_CUR)
  super
end

#handle_ReopenException(ex, &block) ⇒ Object 



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# File 'lib/io/tail.rb', line 314

def handle_ReopenException(ex, &block)
  # Something wrong with the file, attempt to go until its end
  # or at least to read n lines and then proceed to reopening
  until self._file.eof? || @n == 0
    block.call self._file.readline
    @n -= 1 if @n
  end
  super
end

#path ⇒ Object 



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# File 'lib/io/tail.rb', line 244

def path
  self._file.path
end

#puts(o) ⇒ Object 



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# File 'lib/io/tail.rb', line 248

def puts o
  self._file.puts o
end

#readline ⇒ Object 



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# File 'lib/io/tail.rb', line 324

def readline
  self._file.readline
end

#reopen_tailable(mode) ⇒ Object 



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# File 'lib/io/tail.rb', line 346

def reopen_tailable(mode)
  $DEBUG and $stdout.print "Reopening '#{path}', mode = #{mode}.\n"
  @no_read = 0
  self._file.reopen(::File.new(self._file.path, 'rb'))
  if mode == :bottom
    backward
  end
rescue Errno::ESTALE, Errno::ENOENT
  if @reopen_deleted
    sleep @max_interval
    retry
  else
    raise DeletedException
  end
end

#restat ⇒ Object 



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# File 'lib/io/tail.rb', line 328

def restat
  stat = ::File.stat(self._file.path)
  if @stat
    if stat.ino != @stat.ino or stat.dev != @stat.dev
      @stat = nil
      raise ReopenException.new(:top)
    end
    if stat.size < @stat.size
      @stat = nil
      raise ReopenException.new(:top)
    end
  else
    @stat = stat
  end
rescue Errno::ENOENT, Errno::ESTALE
  raise ReopenException
end