PLOGHELP CURRENT_DISK                      Jonathan Laventhol March 1984
                              Revised by Kathryn Seifert  September 1986

Library package for finding out about disk files

Keywords: disk files, operating system


CONTENTS - (Use <ENTER> g to access sections)

 -- INTRODUCTION
 -- AN EXAMPLE INVOLVING 'CURRENT_DISK/1'
 -- AN EXAMPLE INVOLVING 'CURRENT_DISK/3'
 -- EXAMPLE OF USE
 -- RELATED DOCUMENTATION


-- INTRODUCTION -------------------------------------------------------

The CURRENT_DISK library package provides two predicates for finding out
information about disk files.  To load the library file, type:

    ?- library(current_disk).

You will now have the two predicates 'current_disk/1' and
'current_disk/2' available.


-- AN EXAMPLE INVOLVING 'CURRENT_DISK/1' ------------------------------

    ?- current_disk(Name).
    Name = are
    ? ;
    Name = arithmetic
    ? ;
    Name = arrow
    ? 
    yes

The variable Name is unified with an atom for each file in the current
directory.  The format of the name will be dependant on the operating
system you are using; the example above was done under UNIX.


-- AN EXAMPLE INVOLVING 'CURRENT_DISK/3' ------------------------------

Note: The printout in this section was done with the predicate 'portray'
(see PLOGHELP * PORTRAY) defined as:
    portray(X) :- writeq(X).
This makes quotes appear around atoms in the solutions where necessary)

    ?- current_disk('~kaths/pdoc', Nameparts, Statparts).
    Nameparts = ['/cog1/psunb/kaths/pdoc', '', '', '/cog1/psunb/kaths',
                  pdoc, '', '']
    Statparts = [512, 525117464, 0, 177, 16877]
    ? 
    yes

    ?- current_disk('[pop]*.p', Nameparts, Statparts).
    Nameparts = ['_dra2:[pop]grum.p.2', '', '_dra2:', '[pop]', grum, p, 2]
    Statparts = [158, '26-JAN-1984 14:35', 83, 41, 40960] ? ;

    Nameparts = ['_dra2:[pop]temp.p.1', '', '_dra2:', '[pop]', temp, p, 1]
    Statparts = [108, '28-FEB-1984 16:16', 83, 41, 40960] ? ;

    no

The first argument to 'current_disk/3' is an atom representing a file
specification, possibly with wildcards.  The format of this argument is
dependant on the operating system; the first example above is for the
UNIX operating system; the second example is for the VMS operating
system (directory [pop], any name, filetype 'p').  The variable
Nameparts will be unified with a list representing the parts of the
filename.  The parts are atoms in the following format:

        [Fullname, Host, Device, Directory, Name, Type, Version]

the exact format is operating system dependant.  Note that some of the
atoms may be empty. Fullname will be an atom representing
the file (probably the most useful of the entries).

The variable Statparts gets unified with a list of five elements giving
statistics about the file in the following format:

        [Size, Date, Group, Owner, Protection]
            Size is in bytes.
            Date is an atom.  Format dependant on OS.
            Group and Owner are the user's group and user numbers.
            Protection is number representing protection.
                                            Dependant on OS.

If for some reason the statistics cannot be accessed (perhaps you don't
have appropriate privileges) then Statparts will be a list of five
question marks.


-- EXAMPLE OF USE -----------------------------------------------------

You can make predicates to print the current directory:

    dire :-
        (current_disk(X),
        write(X), nl,
        fail);
        true.

Or give you a list of the files, sorted by size:

    dirlist(Spec, X) :-
            fast_bagof(foo(Size, Name),
                       current_disk(Spec, [Name|_], [Size|_]), L),
            keysort(L, X).
                /* see PLOGHELP * KEYSORT, PLOGHELP * BAGOF */

    ?- dirlist('[pop]*.p', X).
        X = [foo(108, '_dra2:[pop]temp.p.1'),
        foo(158, '_dra2:[pop]jcl.p.2')] ? ;
        no


-- RELATED DOCUMENTATION ----------------------------------------------

PLOGHELP * LIBRARIES
 Overview of Prolog library programs