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Re: How to streamingly read text file and display whenever updated text

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On 07.10.2013 03:54, galeomaga@gmail.com wrote:
> https://docs.google.com/file/d/0B2D69u2pweEvelh1T25ra19oZEU/edit?usp=sharing
>

For the readers who don't bother clicking on the link above: It's a 
short video where the OP demonstrates how her/his usage of tail doesn't 
work.

> no matter call tail directly in python or using the script of tail
> all failed
> it seems it can not read next line

In your video you use gedit to write some file and "tail -f <file>" to 
follow it. But "tail -f" will follow the file descriptor. Usually, 
editors like gedit won't save your changes to the original file but 
create a new temporary file and rename it later to the original file 
name after deleting the original one. Thus tail will follow an already 
deleted file.
See also this blog post:
http://tech.shantanugoel.com/2009/12/23/continuous-monitor-tail-fails.html

For your example you will have to use "tail -F <file>" which will follow 
the file name.

Alternatively you could write a simple script to simulate a continously 
growing file like

import time
for i in range(1000):
     with open("test.txt", "a") as f:
         f.write(str(i) + '\n')
     time.sleep(1)

which should work with "tail -f".

Bye, Andreas

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How to streamingly read text file and display whenever updated text galeomaga@gmail.com - 2013-10-05 00:38 -0700
  Re: How to streamingly read text file and display whenever updated text galeomaga@gmail.com - 2013-10-05 00:54 -0700
    Re: How to streamingly read text file and display whenever updated text Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-10-05 09:12 +0100
  Re: How to streamingly read text file and display whenever updated text "James Harris" <james.harris.1@gmail.com> - 2013-10-05 09:06 +0100
    Re: How to streamingly read text file and display whenever updated text Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-10-05 09:14 +0100
  Re: How to streamingly read text file and display whenever updated text Nobody <nobody@nowhere.com> - 2013-10-05 11:25 +0100
  Re: How to streamingly read text file and display whenever updated text Joost Molenaar <j.j.molenaar@gmail.com> - 2013-10-05 13:02 +0200
    Re: How to streamingly read text file and display whenever updated text galeomaga@gmail.com - 2013-10-05 20:17 -0700
      Re: How to streamingly read text file and display whenever updated text Chris Angelico <rosuav@gmail.com> - 2013-10-06 14:28 +1100
      Re: How to streamingly read text file and display whenever updated text Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-10-06 04:06 +0000
        Re: How to streamingly read text file and display whenever updated text galeomaga@gmail.com - 2013-10-06 01:49 -0700
        Re: How to streamingly read text file and display whenever updated text Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-10-06 11:36 +0100
        Re: How to streamingly read text file and display whenever updated text Chris Angelico <rosuav@gmail.com> - 2013-10-06 22:03 +1100
        Re: How to streamingly read text file and display whenever updated text Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-10-06 12:13 +0100
        Re: How to streamingly read text file and display whenever updated text Chris Angelico <rosuav@gmail.com> - 2013-10-06 22:15 +1100
        Re: How to streamingly read text file and display whenever updated text Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-10-06 12:31 +0100
        Re: How to streamingly read text file and display whenever updated text Chris Angelico <rosuav@gmail.com> - 2013-10-06 22:44 +1100
          Re: How to streamingly read text file and display whenever updated text galeomaga@gmail.com - 2013-10-06 18:54 -0700
            Re: How to streamingly read text file and display whenever updated text Andreas Perstinger <andipersti@gmail.com> - 2013-10-07 11:52 +0200
  Re: How to streamingly read text file and display whenever updated text Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-10-05 12:08 +0100

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