[K12OSN] Re: Need script help for fl_teachertool

Robert Arkiletian robark at gmail.com
Wed May 3 03:39:06 UTC 2006

On 5/2/06, Eric Harrison <eharrison at mail.mesd.k12.or.us> wrote:
> Thus anything with ".0.0." in it will match "0.0".
> This should work better for you:
>         getent hosts | grep ^`echo $DISPLAY | sed -e 's/:/ /g'\   | awk '{print $1}'` | cut -f1

Thanks Eric, interesting and clear explanation. But sitting at the
server this returns nothing. I need something. works for me.
Explained below.

> BUT, this is all very convoluted. It has the feeling of approaching a problem
> in the wrong way.  What is the context of what you are working on? There may
> be a cleaner solution.

thanks to you and Jim giving me tips at LinuxFest I was able to speed
up fl_teachertool amazingly. It's FAST now :)
Using the -n like you suggested

netstat -t -e -n | grep :6000 | sed -e 's/:/ /g' | awk '{print $9,$6}'
| sort | uniq

works perfect and like lightning compared to having a dns lookup for
every line of output. So now I have ip's instead of hostnames of all
clients. This is fine BUT I use the $DISPLAY env variable to omit the
terminal machine a teacher (running fl_TT) is sitting at (for obvious
reasons like logging yourself out) So I have to omit the teacher
terminal by omitting the ip which matches the $DISPLAY.  That's why works. Since none of the terminals have this ip none are
omitted (which is what I want when someone runs fl_TT from the
This line

cat /etc/hosts | grep `echo $DISPLAY | cut -d: -f1` | cut -f1

works when running fl_TT on a terminal but not properly if the teacher
runs fl_TT on the server (as you noticed)

Long story short. Basically I just need fl_teachertool to figure out
the ip of the terminal which it's running on and if running on the
server it needs to give me an ip which none of the terminals would
have eg. or so no match to omit is found. The
only method of determining the ip of the terminals I know of is to get
the $DISPLAY var and find it's corresponding ip in /etc/hosts (since I
can't assume ws222.ltsp is If you know an easier way
I'd love to hear it.

Hope this is not as clear as mud.
Robert Arkiletian
Fl_TeacherTool http://fltk.org/links.php?V269
C++ GUI tutorial http://fltk.org/links.php?V19

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