Ah!, now I understand you . I think that you won’t be able to get around it that easy as I think the command line way would still require an app to be installed?.
The link below may/may not be of help to you?:
There is a button on my Logitec webcam but it doesn’t do anything in Linux!. 
Maybe one of these might prove useful to you?:
https://filmora.wondershare.com/video-editing-tips/screen-capture-tools-for-linux.html