Using [ChatSetAttr], don't know how to provide charids

I'd like to setup my character sheets to have a shared attribute (a party resource) between each other. I figured I'd make use of ChatSetAttr to silently send a message to all the player-characters whenever the value is adjusted. I could probably simply use --all since I will likely only have the player characters but it might be useful to know where I can get a character id so I can list them in my script. Some of the player's haven't settled on a character name but I'd like to have the script going. 

Select a token representing the character. Enter into chat: @{selected|character_id} Don't forget that the leading dash is part of the id.

Is there a way to provide the character id as a hard value?

I'm dumb, I just realized you were suggesting I do the command in chat. Thank you!