I had a question today about sharing the contents of a directory with other users, linked to my alog I posted last week about how CDS ensures files under /opt/rtcds/userapps are shared between users of the controls group.

If, for example, you have a directory in your home area which you wish to share with everyone, you need to change the group ownership to controls and set the permission of the directory to 2775

chgrp controls <directory-name>

chmod 2775 <directory-name>

the directory permissions should now be

drwxrwsr-x   2 david.barker controls              2 Mar 14 16:50 directory_name

https://cdswiki.ligo-wa.caltech.edu/wiki/LinuxFilePermissionsExplained