How do you change a user's primary group as they change directory

[whir]

User1 is a member of Group1, Group2 and Group3, each group has a directory (say /home/group1, /home/group2, ...)

How do I make it so that when User1 cds to /home/group1, their primary group becomes group1, when they cd to group2 they become group2, etc?

Essentially, I'm only looking to do this so that when User1 makes a new file in each respective directory, it can be set group writable for the appropriate group.

I will be doing this on Solaris 10 (Although I am testing on Ubuntu 8.10...)

Thanks!

[kaarthikeyapreyan]

I suggest that u set up a cron that updates the permission once a file is created or check for any new file in the corresponding directory and update its permissions.

[Nepomuk]

Another option would be to overload the cd command with a local script, so that if checks if the directory that it's changing to is in one of these places and if so change the default group.

Greetings,
Nepomuk

[kvmreddy]

Change group owner ship of each directory first, then add setgid bit on each
directory. setgid allows to inherit parent directory GID, when file or
directory created in that directory. To know mor about setgid, setuid
check bellow link.
Advanced Linux/UNIX file permissions

[ennoil]

To do what you want, as written, is impossible. To change a user's primary group requires them to log out and log back in again. You will need to, as suggested above, use setGID to allow users to act on the directory as the primary group.