Linux Gazette

   ...making Linux just a little more fun!

May 2005 (#114):

     * [1]The Mailbag
     * [2]The Answer Gang
     * [3]News Bytes, by Michael Conry
     * [4]Python for scientific use. Part I: Data Visualization, by Anders
       Andreasen
     * [5]A Tale of Three Conferences, by Howard Dyckoff
     * [6]Secure Knoppix on CD-ROM for Disaster Recovery, by Edgar Howell
     * [7]Shelling your Linux box with Festival, by Maxin B. John
     * [8]Right To Your Own Devices, by Kapil Hari Paranjape
     * [9]Lock It Down With Arno's iptables-firewall, by S. Keeling
     * [10]Introduction to Shell Scripting, part 4, by Ben Okopnik
     * [11]Measure CPU Fan Speed with an RTAI/LXRT Stroboscope!, by Pramode
       C.E.
     * [12]HelpDex, by Shane Collinge
     * [13]Qubism, by Jon "Sir Flakey" Harsem
     * [14]PmWiki - Wiki the Painless Way, by Raj Shekhar
     * [15]The Foolish Things We Do With Our Computers, by Ben Okopnik
     * [16]The Linux Launderette

The Mailbag
     _________________________________________________________________

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   Submit comments about articles, or articles themselves (after reading
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     * [20]Python, tail -f, pyurlview, non-blocking I/O
     * [21]Which flavour?!
            ____________________________________________________

Python, tail -f, pyurlview, non-blocking I/O

   Mon, 28 Mar 2005 05:03:50 +0100
   Thomas Adam ([22]thomas from edulinux.homeunix.org)

   Hello,

   I'm hoping this will drum up some replies. I'm tumbling head-first into the
   world of python and ncurses for this, and know very little about both.

   To cut a long (and rather boring) story short, I run [23]irssi in a screen
   session on my poor P166 server. X11-forwarding is not an option as I don't
   have nor want X11 installed, and it's damn slow even if I did. But one
   useful feature is using one of the many scripts off of irssi's website, I
   can get irssi to scrape urls into a text file. "Wooooo, I hear you say".

   Well, it is nice. And thanks to network transparency, I am able to tail that
   logfile via shfs (ssh filesystem, essentially). So then I got to thinking.
   What's  an easy way of displaying the URLs in the file? I remembered a
   program that ships (often) with mutt -- "urlview". It scans a file for a
   regexp for URLs and presents a means of selecting them and launching them.
   Brilliant. Except... it expects a file -- piping to stdin blocks.

   Bah! I don't want to hack the source-code, unblocked I/O in C is a headache.
   So I stumbled across pyurlview [1] a replacement written in Python. It's
   "ok" and is in a language I can read.

   What I'm wanting to do is emulate this:

tail -f ./some_file | pyurlview

   Now that doesn't work as-is. So I thought about it a bit, and came up with
   this little bit of python code (which I hope is the correct "way" to do it):

#! /usr/bin/env python
import os,sys

while 1:
  #sys.stdin.fileno()
  s = sys.stdin.readline()
  print "Got", s

   Which seems to work when one does:

tail -f ./foo | testfile.py

   So I thought I'd try and incorporate that idea into the pyurlview script [1]
   I tried all I might, to no avail. The closest I got was here [2] but that's
   mangling everything and isn't functioning like in the example I correctly
   showed above.

   So if someone can see the error in logic, do say. Or does anyone know of an
   existing program that will do what I want? I can use any form of scripting
   language to do it (awk, ruby, etc) already -- but it's more the curses and
   non-blocking I/O I'm interested about. Plus, I'd rather not reinvent the
   wheel, hence battling it out with python. maybe I could use 'multitail' but
   it's UI sucks for what I am wanting.

   Thanks In Advance,

   -- Thomas Adam