UNIX for Beginners Questions & Answers

I have a textfile with a list of strings I want to monitor in my network.

alertlist:

Code:

hans
franz
tanz

So it can output for me whenever the a strings it matched:

Code:

#!/bin/sh
while : ; do
    testfile="/var/media/ftp/alertlist.txt"
  [[ -f "$testfile" ]] && echo "${testfile##*/} exists." ||  echo "${testfile##*/} does not exist."
  while /var/media/ftp/look.sh active | grep -i -f  /var/media/ftp/alertlist.txt
  do
???
        sleep 4 
    done
    sleep 4
done&

Now what I want is eh a notification, whenever the state changes, example, hans joins, franz leaves franz and tanz joins etc.

not when found or nor, only when the situation changes

how can I do this while keepin the I/O to the flashdrives to a minimum?

Hmm. Quick question - if a process or user is blacklisted correctly - iptables in linux can do this for you - then it never, ever get your system to start with. Why do you allow them to get going on your system to start with??

The tool to block access by IP is OS dependent. I gave a linux example.

this is more for that I'm informed if specific people are coming or nearby to my place via wifi

okay blacklist is misleading here, it is more an "alert list"

I have optimized the question. I hope it is clearer now...

I just want to do soemthing in this loop, if one the strings in the textfile apear in the shell output the first time, or when they disappear, or re appear..

If you want to keep I/O to a flashdrive to a minimum, why are you accessing that flashdrive at least four times every 4 seconds?

If you have a list of strings to search for, why do you have to test every four seconds whether or not your list exists? Does this list change frequently while you're running your script?

If you have a program you want to run every 4 seconds and you want to minimize accesses to a flashdrive, why is the program you want to run on a flashdrive?

What does /var/media/ftp/look.sh do? Does it invoke any other software that is located on that flashdrive? Does it access any other files that are located on that flashdrive?

Why are any of these files on a flashdrive if you don't want to access the flashdrive?

What output does /var/media/ftp/look.sh produce? Is the output just strings exactly matching the format of the strings in /var/media/ftp/alertlist.txt, or do lines in the output contain additional text that needs to be stripped away as part of your output?

Can a string in /var/media/ftp/alertlist.txt appear in the output from /var/media/ftp/look.sh more than once? If so, does the output from your script need to notice differences in the number of times a string is found? Or, does it just need to notice when the number of times a given string string appears changes from zero to non-zero and from non-zero to zero?

Does you output just need to give a list of the strings that changed status? Or does the output need to report strings that appeared and strings that disappeared, or the number of times a string appeared in the latest time through the loop?

If these strings are people's names or login IDs, do you really need case insensitive matches? Are UserName and username to be treated as different strings or as a single string?

Thats a good point! I need to fix this. 8-)

The list changes, but reading it once every hour should be sufficient

If you have a program you want to run every 4 seconds and you want to minimize accesses to a flashdrive, why is the program you want to run on a flashdrive?

Look.sh calls a system internal function which goes through a set of arrays with which you can output several information. in this case I just let output clients in the network and its state (active/online)

it is how it is...

lines in the output like in the alertlist.txt

If you mean as a part of a string yes. so if alertlist.txt contains hans, look.sh could output this what I would like to have considered

hans
hansolo
Hansala

Hans joined
Hansala left
Hans left
hansolo joined

etc...

ideally yes

I saw there is a watch command available
This should display all output differences? can maybe this be used for this?

can this be used to just consider the data in the lists?

watch - Repeat Linux / Unix Command Regular Intervals