I often create a multiuser GNU screen session for demonstration purposes. I do it by creating a named session with:

screen -S tutorial

And then performing

^A:multiuser on
^Aaclchg student1,student2,student3,... -wx "#?"

And that works, the students can connect with screen -r grochmal/tutorial and can see what I do. (It even locks their PTS 'cause they do not have permission for ^Ad).


What I'd like to do though is to setup aclumask so I could make my life easier since I sometimes forget to use aclchg and use acladd (and a funny student can write swear words on the terminal).

According to how I understand man screen the following should be equivalent to what I do above:

screen -S tutorial
^A:multiuser on
^A:aclumask ?-wx
^A:acladd student1,student2,student3,...

And then I could add the aclumask ?-wx to my .screenrc and never worry again about funny students.

Unfortunately that is not the case, and the aclumask line seems to have no effect on the permissions granted by acladd. I must be doing something wrong.

What is the proper way of using aclumask with users that are not yet known to screen?

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