Tail, start reading at EOF

ruby-talk
1

Hi,

how to alter tail function to start at the end
of the file, not reading the lines already existing in file ? =

File = File.open(ARGV[0])
while File.exists?(file.path)
    puts file.gets while !file.eof?
    sleep(1)
end

Regards, Gilbert

2

Hi,

how to alter tail function to start at the end
of the file, not reading the lines already existing in file ? =

  file.seek 0, IO::SEEK_END

File = File.open(ARGV[0])
while File.exists?(file.path)
    puts file.gets while !file.eof?
    sleep(1)
end

File#eof? does not work here. When the file has been
extended it still returns true even though File#gets will
return a String object.

Bertram

···

Am Mittwoch, 22. Aug 2007, 18:20:12 +0900 schrieb Rebhan, Gilbert:

--
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-scharpf.de

3

/*
Hi,

how to alter tail function to start at the end
of the file, not reading the lines already existing in file ? =

  file.seek 0, IO::SEEK_END
*/

thanks, with your pointer and an older post by Robert Klemme
i have a working solution now =

def tail(file, interval=1)
   raise "Illegal interval #{interval}" if interval < 0

   File.open(file) do |io|
      io.seek 0, IO::SEEK_END
     loop do
       while ( line = io.gets )
         puts line
       end
       # uncomment next to watch what is happening
       puts "-"
       sleep interval
     end
   end
end

Anything to improve ?

Regards, Gilbert

···

-----Original Message-----
From: Bertram Scharpf [mailto:lists@bertram-scharpf.de]
Sent: Wednesday, August 22, 2007 12:14 PM
To: ruby-talk ML
Subject: Re: tail, start reading at EOF

Am Mittwoch, 22. Aug 2007, 18:20:12 +0900 schrieb Rebhan, Gilbert:

4

gem install file-tail

Then look at the rdoc for it. There's an example that does an implementation of the Unix tail command. It's a lot more capable that what you have here, but if you wanted to start some number of lines before the EOF, the file-tail gem is really what you want.

-Rob

Rob Biedenharn http://agileconsultingllc.com
Rob@AgileConsultingLLC.com

···

On Aug 22, 2007, at 6:27 AM, Rebhan, Gilbert wrote:

-----Original Message-----
From: Bertram Scharpf [mailto:lists@bertram-scharpf.de]
Sent: Wednesday, August 22, 2007 12:14 PM
To: ruby-talk ML
Subject: Re: tail, start reading at EOF

/*
Hi,

Am Mittwoch, 22. Aug 2007, 18:20:12 +0900 schrieb Rebhan, Gilbert:

how to alter tail function to start at the end
of the file, not reading the lines already existing in file ? =

  file.seek 0, IO::SEEK_END
*/

thanks, with your pointer and an older post by Robert Klemme
i have a working solution now =

def tail(file, interval=1)
   raise "Illegal interval #{interval}" if interval < 0

   File.open(file) do |io|
      io.seek 0, IO::SEEK_END
     loop do
       while ( line = io.gets )
         puts line
       end
       # uncomment next to watch what is happening
       puts "-"
       sleep interval
     end
   end
end

Anything to improve ?

Regards, Gilbert