Grant accesses in Linux

    Grant read access (r) to a file to all members of your group (g):
    chmod g+r file-name
    Grant read access to a directory to all members your group:
    chmod g+rx directory-name
    Note that "execute" permission is required in order to read a directory.
    Grant read permissions to everyone on the system to a file which you own so that everyone may read it: (u)ser, (g)roup and (o)ther.
    chmod ugo+r file-name
    Grant read permissions on a directory to everyone on the system:
    chmod ugo+rx directory-name
    Grant modify or delete permissions to a file which you own for everyone in the group:
    chmod ugo+rw file-name
    Note: In order for modify and delete permissions to be useful, one must be able to modify the directory in which the file is located: chmod ugo+rwx ./
    Deny read access to a file by everyone except yourself:
    chmod go-r file-name
    Allow everyone in your group to be able to modify the file:
    chmod 660 file-name