*command
**
ALTER command
Form:           ALTER   "NAME/A,ACCESS/A"
Purpose:        To alter the access matrix associated with a directory entry.
Author:         MFR

Specification:

NAME is the name of a filing system file or directory (strictly, the
    directory entry referring to it).

ACCESS is an access matrix, in the form
                      /v-part/x-part/y-part/z-part

    Each of the parts can contain any combination (possibly empty) of the
    characters
                      CVXZY, RWE, DAU

    Provided that no protection violation occurs the access matrix will be set
    to the specified value. Note that the filing machine will not permit
    matrices to be created which have neither D(elete) not A(lter) access.
    See HELP ACCESS MATRIX for further information.

    Parts may be omitted, eg ( /v-part/x-part ) if no access is to be given
    to trailing parts. Note that no check is made that the bits specified (ie.,
    CVXYZ or RWE) are appropriate to the object type, although no irrevocable
    damage can ensue (you'll just get an unexpected access matrix as the
    result).

    The ACCESS field may also be given as the string "default".  This will,
    if allowed, set the matrix to the default value for the given object type.
    At the time of writing this is /DAURW/ARW/RW/R for a file and
    /ACV/ACX/CY/Z for a directory.

Example:        ALTER WOMBAT /DAURW/ARW//R
                ALTER WOMBAT DEFAULT
                ALTER POSSUM /D
                ALTER MYDIR /ACVXY/Z/Z/Z


