In the web I have found a script called "Autosuspend".

I'm no programmer. But it is my understanding that the part of the script below looks for active clients on port 9981 and 9982.
Though I have one or more active clients on port 9982 the variable "$active_clients" never gets TRUE.
Can someone tell me if there is a mistake in this part of the script.

The script is running on Linux Mint 20.



Here is the part of the script that is not working

TVHEADEND_IP=$(echo ${TVHEADEND_IP:-$(hostname -I)} | tr -d [:space:])
TVHEADEND_HTTP_PORT=${TVHEADEND_HTTP_PORT:-9981}
TVHEADEND_HTSP_PORT=${TVHEADEND_HTSP_PORT:-9982}

TVHEADEND_PORTS="$TVHEADEND_HTTP_PORT $TVHEADEND_HTSP_PORT"
LANG=C
active_clients=()
for port in $TVHEADEND_PORTS; do
IFS=$'\n' active_clients+=($(netstat -n | grep -oP "$TVHEADEND_IP:$port\s+\K([^\s]+)(?=:\d+\s+ESTABLISHED)"))
done
if [ $active_clients ]; then
logit "Tvheadend has active clients: ${active_clients[@]}"
return 1
fi

hostname -I may return more than one IP address. Provided TVHEADEND_IP is not set elsewhere, this code won't work in that case.

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looks like the same problem as your other post. What I don't really understand: how do you want to solve it if you are not a programmer. [How] Do you think without any knowledge a script named autosuspend will do what you need? How do you know that part of the code which is not working?

You can debug your code with set -xv.
hostname -I may return more than one IP addresses, in that case the script cannot work.

By the way, would be nice to post your code in code tags.

2 members found this post helpful.

@ pan64
When I was younger I programmed a little bit (Basic, Turbo Pascal, C++).

In principle I understand in which way the script "autosuspend" is working. I already checked some parts of the script. I checked e.g. that the "FOR DO" loop is running two times. And I understand that my pc is not running down when "$active_clients" is TRUE. But " $active_clients" never gets TRUE. That's why I try do understand this line
IFS=$'\n' active_clients+=($(netstat -n | grep -oP "$TVHEADEND_IP:$port\s+\K([^\s]+)(?=:\d+\s+ESTABLISHED)"))

Can you check if there is a mistake in this line?

I understand that this part of the script should check if there is traffic on port 9981 and 9982 of the localhost. If there is traffic "$active_clients" gets TRUE.

yes, I can check and I think that line is correct. what we found is the very first line (containing hostname -I). But without details hard to say more

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https://www.shellcheck.net/

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netstat is a legacy tool, nowadays many would rather prefer ss. Something like
Other than that the command looks OK.

I think the prefix
IFS=$'\n'
has no effect, can be omitted.

The prefix sets an environment for a forked shell, such as a command.
But an assignment = or += is not a command; no fork happens.
The environment is only set for the $( ) sub shell where it has no effect, neither in netstat nor in grep.

TVHEADEND_IP=$(echo ${TVHEADEND_IP:-$(hostname -I)} | tr -d [:space:])
should be
[ "$TVHEADEND_IP" ] || read TVHEADEND_IP junk < <(hostname -i)
or
[ "$TVHEADEND_IP" ] || TVHEADEND_IP=( $(hostname -i) )

The script should be entirely rewritten...

Thank you for all this hints here. But I still don't understand how to change this line now.
IFS=$'\n' active_clients+=($(netstat -n | grep -oP "$TVHEADEND_IP:$port\s+\K([^\s]+)(?=:\d+\s+ESTABLISHED)"))

I tested again a little bit.
When I have NO active client and write in the terminal this
netstat -n | grep -oP 192.168.178.60:9982
I get as result "nothing".

When I have AN active client and write in the terminal this
netstat -n | grep -oP 192.168.178.60:9982
I get this line as result
192.168.178.60:9982

So my script needs to do something like this:
active_clients=()
if [ (netstat -n | grep -oP 192.168.178.60:9982) = (192.168.178.60:9982) ]; then
logit "Tvheadend has active clients: ${active_clients[@]}"
return 1
fi

It is my understanding that "return 1" means that "active_clients=1" right?
Can this work? What do I have to change in my script?

Nice weekend!

could you be so kind as to click the advance and then click code then insert it in the code brackets Thank you

On my Mint 20 VM since there is a line in /etc/hosts i.e. 127.0.1.1 <hostname> and there are no other virtual ports besides lo, hostname -I is the correct syntax. However, since I don't know exactly how your system is configured make sure the output is as expected. Run the command from a terminal.

hostname -I

There are a few statements that could be rewritten but the partial script "as is" works on my Mint 20 VM. I used ssh port 22 as a test instead of 9981,9982. I assume logit is a function and I did not need the return statement.

I believe since $active_clients is an array the if statement checks if there an element 0. If there is the statement is true.

There could be other problems with the script.

See my terminal output

I hoped that it is an easy and good idea what I have written here. No one an idea how this part of the script should look like?