How do you use "value" with shell integration

Hi all,

I’ve gone through the documentation but I don’t get hox I am supposed to get the output of a shell command. The doc says:

With a 0 exit code, the output (stdout) of the command is used as value

How I am supposed to interpret this ? Here is what I’ve tried (and does not work ^^):

alias: "My script"
  - service: shell_command.sync_backup_folder
    data: {}
  - service: system_log.write
      level: warning
      message: "{{ value }}"