A placeholder cannot be used to disable the admin interface about caddy

[francislavoie]

You have to use the {$ENV} style: https://caddyserver.com/docs/caddyfile/concepts#environment-variables

[jpluscplusm]

You have to use the {$ENV} style

I thought that style was only available inside a Caddyfile - how does the JSON-config-producing user control the setting through the environment, in the scenario I outlined?

[francislavoie]

Currently, you don't - you're right that's a limitation right now. But you quoted using a Caddyfile so that's my suggestion.

[jpluscplusm]

that's a limitation right now.

Would you like me to open an issue tracking this?

[francislavoie]

If you're using JSON, then just set admin.disabled to true. https://caddyserver.com/docs/json/admin/

admin off is just a Caddyfile config shortcut for the disabled property. I don't think it makes sense to complicate JSON by overloading listen to possibly also disable. That's out of scope of the listen config property.

That said, I just checked the code, and {env.SOME_VAR} will work for using an env var to set the listen address. But it doesn't work to turn off admin (and I don't think it should work either).