Using Environment Variables in settings.js

[stokes776]

Hello,

I am trying to dynamically set my pageTitle.

    "editorTheme": {
        "page": {
            "title": "${BALENA_DEVICE_NAME_AT_INIT}"
        }
    }

I use Balena, and it has an environment variable, that is accessible from within the Node-Red container named BALENA_DEVICE_NAME_AT_INIT.

I tried inserting the environment variable like I have done before in the flows.json, but when its in the settings.js it doesnt seem to work.

Is there a way to use Environment Varaibles within the settings.js?

[TotallyInformation]

settings.js is a node.js file so you need to use the node libraries to access the env vars.

How to read environment variables from Node.js (nodejs.dev)

[jbudd]

No idea if this will work with Balena, but I use this script to change the editor page header and browser tab title for editor and dashboard. I hope its some use to you.

#! /bin/bash
# Change node-red editor page header to show hostname & IP. Make dashboard browser tab show hostname
############################################
DIR=/home/pi/.node-red

# Uses gawk. Probably not needed but a useful catch before running on an unknown system
gawk -V >/dev/null || { echo Please install gawk; exit 1; }
# Does /home/pi/bin/ipaddress exist?
IP=/home/pi/bin/ipaddress
test -x $IP || { echo "This program needs (missing) $IP - quitting." ; exit 1; } # {} groups commands, need ; after last command.

checkfile()
{
  file=$1; string=$2
  if test ! -f $file
  then
     echo $file not found; return 1
  elif grep $string $file >/dev/null
  then
     echo $string is already in $file - Not changed
     return 1
  fi
}

echo "=============================================== settings.js ..." # 2 insertions, above module.exports and below editorTheme
FILE=$DIR/settings.js
checkfile $FILE "process.env.HOSTNAME" || exit 1
cp $FILE $FILE.bak || exit 1
gawk ' { if ($0 ~ /^module.exports =/) {
                                          print "// ----------- added by script ----------"
                                          print " hostname = require('\''os'\'').hostname();"
                                          print " const execSync = require('\''child_process'\'').execSync;"
                                          print " const ipaddress = execSync('\''/home/pi/bin/ipaddress'\'', { encoding: '\''utf-8'\'' });"
                                          print " device = hostname + '\'' '\'' + ipaddress;"
                                          print " process.env.HOSTNAME = hostname;"
                                          print " process.env.DEVICE = device;"
                                          print "// --------------------------------------"
                                          print
                                      }
        else if ($0 ~ /editorTheme: {/) {
                                          print
                                          print "// ----------- added by script ----------"
                                          print "       header: {"
                                          print "          title: process.env.DEVICE"
                                          print "       },"
                                          print "       page: {"
                                          print "          title: process.env.DEVICE"
                                          print "       },"
                                          print "// --------------------------------------"
                                      }
        else print
      }' $FILE > $FILE.tmp
echo $FILE was changed. Original saved as $FILE.bak
echo
mv $FILE.tmp $FILE || exit 1

FLOWFILE=$(grep "^[[:space:]]*flowFile:" $FILE | cut -d "'" -f2)  # flows file may be defined in settings.js
if [ "$FLOWFILE" == "" ]; then FLOWFILE=flows_$HOSTNAME.json ; fi # default value
FILE=$DIR/$FLOWFILE
echo "=============================================== $FLOWFILE ..." # Make dashboard tab on browser = hostname

checkfile $FILE HOSTNAME || exit 1
cp $FILE $FILE.bak || exit 1
sed -i s/"Node-RED Dashboard"/'${HOSTNAME}'/ $FILE
if  cmp $FILE $FILE.bak >/dev/null
then
   echo $FILE was not changed.
   rm $FILE.bak
else
   echo $FILE was changed. Original saved as $FILE.bak
fi
echo

echo Finished. Restart node-red to activate changes.

(I think the change in the flows file is only for the dashboard, and I'm not convinced it's working! )

Oh - It calls /home/pi/bin/ipaddress:

#! /bin/bash
# Print the eth0 else wlan0 IP address

for IFACE in eth0 wlan0
do
   IP=$(ifconfig $IFACE 2>/dev/null | awk ' /broadcast/ {print  $2 }' )
   if [ "$IP" ]
   then
      echo $IP
      exit 0
   fi
done

On my Pi with HOSTNAME = "Crucial" It changes appearance from this

to this

[stokes776]

Thank you guys, I had not even considered changing that header within the page, that is something I will add in as well.

For anyone coming across this in the future, this is what worked for me, that I will expand upon:

My settings.js is very small, only containing the things I need.

setting a var at the top, and then using that within the JSON, the trick to access the ENV variable, as mentioned by someone who replied up above, is process.env.ENVIRONMENTVARIABLENAME