Creating custom sensor

[sullen perch]

Hi all!
I would like to create an add-on what can follow my stock portfolio's value and visualize it. The add-on is ready to use, I can install in HA OS also and I have an automation trigger to update the portfolio data regularly. This portfolio date is saved in a json file in /share folder. The next step should be to create a custom sensor to read the json data and make accessible in visualization.

My json file content is something:
{
"timestamp": "2025-07-18T10:26:00+02:00",
"summary": [
{
"buy_price": 18747.3,
"portfolio_value": 1866.2,
"gain_percent": -0.36,
"gain_huf": -631.11
}
]
}

The sensor definition is:

• platform: command_line
  name: portfolio value
  command: "cat /share/portfolio_log.json"
  scan_interval: 60
  json_attributes_path: "$.summary" # Example path, adjust as needed
  json_attributes:
  • "buy_price"
  • "portfolio_value"
  • "gain_percent"
  • "gain_huf"

The problem is this sensor doesn't exist in my HA system after a reboot, I cannot see any error log in system log. I tried some other option like jq instead of cat and value_templates, etc... Sometimes this sensor appears in my HA system but doesn't get any value from file.
I try to seek in documentation, google and AI, but didn't find any solution yet. I saw many people using rest platform for reading json, but this filed is not published.

Any suggestion or solution?

Thanks in advance

Ps.: if it's in wrong topic please let me know and move to the right one.

Creating custom sensor

[tawny path]

Your configuration is under the wrong integration

Also, your JSON attributes path needs to reference a dict, right now it references a list

You need something like

command_line:
  - sensor:
      name: portfolio value
      command: "cat /share/portfolio_log.json"
      scan_interval: 60
      json_attributes_path: "$.summary[0]"
      json_attributes:
        - "buy_price"
        - "portfolio_value"
        - "gain_percent"
        - "gain_huf"