Generate a json with variable value from a file using bash

Question

I have a fleet of raspberry pi's running as access points. I set the default SSID and PASSWORD using a simple bash script that runs at boot. I get unique values for this:

SSID = cat /sys/class/net/wlan0/address | tail -c 10 | tr -d ":"

PW = cat /proc/cpuinfo | tail -c 9

I just echo the results on the hostapd file, everything work just fine, each Raspberry Pi get unique SSID and PW. Now I need to generate a JSON file with this values (via bash) in a format like this.

{
  "wifi": {
    "ssid": "SSID",
    "pw": "PW"
  }
}

Can anyone shed some light on this?

Regards

Answer 1

Heredocs perform variable expansion, so you can do something like

SSID=$(cat /sys/class/net/wlan0/address | tail -c 10 | tr -d ":")
PW=$(cat /proc/cpuinfo | tail -c 9)

cat >./config.json <<EOF
    {
      "wifi": {
          "ssid": "$SSID",
          "pw":   "$PW"
      }
    }
EOF