i have a one large server, we are divude in theree group in company, one group member do not view another group member,but some files are shared in two teams, how can its passible.

Move the three user groups into different unix groups. usermod will allow you to change user groups. You can add a single user to many groups as well. Change the ownership of the files (and directories) you want to restrict access to with chown. Then, if you chmod 660 the restricted files, they will not be accessible to anyone outside the groups that have been granted permission to view them (and root). ex) user1, user2, user3 user1 : group1, group2 user2 : group2, group3 user3 : group3 file1 : chown user1:group2 660 - user1 and user2 can access (rw) file2 : chown user2:group3 640 - user2 has rw access, user3 has r only access file3 : chown user1:group1 660 - user1 is the only one with access (rw).