I have found a node/npm program which monitors electricity usage on energy-monitoring TPLink smart switches. It is supplied with a shell script (listed below) which I am calling from /etc/rc.local

/home/pi/tplink/tplink-energy-monitor/tplink-start.sh

#!/bin/bash

cd /home/pi/tplink/tplink-energy-monitor
npm start &


/etc/rc.local (the operative line is the execution of /home/pi/tplink/tplink-energy-monitor/tplink-start.sh)


#!/bin/sh -e
#
# rc.local
#
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
printf "My IP address is %s\n" "$_IP"
fi

# start monitoring the energy usage of the freezers and other TPLink
HS110 start plugs
/home/pi/tplink/tplink-energy-monitor/tplink-start.sh

exit 0


rc.local has the attributes

-rwxr-xr-x 1 root root 562 Sep 19 19:49 rc.local

so it is executable by everyone. I presume it is run as root, so similar to being logged in as a non-root user but using sudo.



This appears to start node and npm, as well as the app.js

ps -alef | grep node lists

0 S root 1907 1894 0 80 0 - 473 - 19:05 pts/1 00:00:00
sh -c node ./app.js
4 S root 1908 1907 4 80 0 - 38800 - 19:05 pts/1 00:00:21
node ./app.js

and

ps -alef | grep npm lists

4 S root 1894 1 0 80 0 - 33909 - 19:05 pts/1 00:00:02
npm


However the web interface that the app presents (for displaying graphs of electricity usage) fails to locate smart plug devices.

Starting the script manually works fine:

(start a Terminal window)


sudo /home/pi/tplink/tplink-energy-monitor/tplink-start.sh &





What is the best remedy for running the script automatically at boot time? Should the rc.local entry have a "&" on the end so it runs in the
background? Is it a problem with the script expecting to run in a Terminal window that continues to have stdout?

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On Mon, 19 Sep 2022 20:00:02 +0100, "NY" <me@privacy.invalid> declaimed the following:

What is the best remedy for running the script automatically at boot time? >Should the rc.local entry have a "&" on the end so it runs in the
background? Is it a problem with the script expecting to run in a Terminal >window that continues to have stdout?

Cron job in the /user/ account (since you claim manual start works -- unless you are using sudo to start it). I believe @reboot is an option for specifying when to run. Might need to add a short delay to ensure enough of
the OS is up to support the task.



--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com http://wlfraed.microdiversity.freeddns.org/

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NY <me@privacy.invalid> wrote:

However the web interface that the app presents (for displaying graphs of electricity usage) fails to locate smart plug devices.

Starting the script manually works fine:

(start a Terminal window)

sudo /home/pi/tplink/tplink-energy-monitor/tplink-start.sh &

Does it work if you start it as the root user instead of using
sudo? When you use sudo, environment variables such as $HOME remain
set to the value for the user who runs the sudo command. If you
"sudo su" and then run the command, that is the same environment
where rc.local will start the script, where $HOME will be "/root".

What is the best remedy for running the script automatically at boot time? Should the rc.local entry have a "&" on the end so it runs in the
background?

No, because tplink-start.sh appears to background the main task
itself.

Is it a problem with the script expecting to run in a Terminal
window that continues to have stdout?

Maybe, I don't know anything about Node JS. The fact that looking
up "npm" finds descriptions of it as a package manager confuses me
already.

--
__ __
#_ < |\| |< _#

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On 20-09-2022 00:32, Computer Nerd Kev wrote:

NY <me@privacy.invalid> wrote:

However the web interface that the app presents (for displaying graphs of
electricity usage) fails to locate smart plug devices.

Starting the script manually works fine:

(start a Terminal window)


sudo /home/pi/tplink/tplink-energy-monitor/tplink-start.sh &

Does it work if you start it as the root user instead of using
sudo? When you use sudo, environment variables such as $HOME remain
set to the value for the user who runs the sudo command. If you
"sudo su" and then run the command, that is the same environment
where rc.local will start the script, where $HOME will be "/root".

This seems like a good test. Also, isn't bash disallowed in system
scripts like rc.local, or is that old info, or just wrong..? Might be
worth trying to change bash to sh in the tplink-start.sh script because
it doesn't use any bash features anyway.

What is the best remedy for running the script automatically at boot time? >> Should the rc.local entry have a "&" on the end so it runs in the
background?

No, because tplink-start.sh appears to background the main task
itself.

Yes, and so it's also unnecessary on the command line, like quoted above.

Is it a problem with the script expecting to run in a Terminal
window that continues to have stdout?

Maybe, I don't know anything about Node JS. The fact that looking
up "npm" finds descriptions of it as a package manager confuses me
already.

It's because it's more than simply a javascript interpreter/jit
compiler, although in the case of "npm start" the only thing it does is
look up the relevant "start" directive in an accompanying package file
and invoke node to execute the file listed there.

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