From: Daniel Berger <djberge@...55host11.interprise.com>
Date: 2002-07-30T05:15:25+09:00
Subject: A very basic tail -f implementation

Hi all,

I've been playing with a Ruby implementation of the *nix 'tail' command.  Here's 
what I've come up with so far.  I thought I'd put it out there for comment and see 
what people think.

It doesn't do anything fancy - it's not nearly as smart as it's Perl equivalent yet, 
for example.  But, it works.

Requires 1.7.2 (for the sysseek method).

# While this is running, try doing
# "echo 'sometext' >> test.txt" once in a while
require 'tail'
t = Tail.new("test.txt") # Or whatever

# Ctrl-C to exit
while true
   puts t.read
end

# Da code
class Tail

   attr_accessor :file, :buffer, :interval

   def initialize(file, buffer=8192, interval=10)
      @file = file
      @buffer = buffer
      @interval = interval

      @fh = File.open(file,"r")
      @fh.sysseek(-1,2)
   end

   def read
      begin
         return @fh.sysread(buffer).tr("\n","")
      rescue EOFError
         @fh.sysseek(-1,2)
         sleep interval
         retry
      end
   end
end