/sys$common/syshlp/DFUHLP.HLB  —  DFU  DIRECTORY
 The DIRECTORY command provides 7 different functions depending on the
 qualifiers used.
 Syntax:
    DIRECTORY/COMPRESS <file>
    Compresses one or more directories.

    DIRECTORY/DUMP <file>
    Provides a block level dump of a directory

    DIRECTORY/REBUILD_MFD <device>
    Recovers a corrupted MFD directory (000000.DIR)

    DIRECTORY/RECOVER <file>
    Recovers a corrupted directory

    DIRECTORY/ALIAS <device>
    Searches all directories on the device for alias file entries

    DIRECTORY/EMPTY <device>
    Searches the disk for empty directories.

    DIRECTORY/VERSION=n <device>
    Searches all directories on the device for files which
    have at least n versions.

 The qualifiers /ALIAS, /EMPTY, and /VERSION can be
 combined in one command.
 Other combinations of qualifiers are not possible.

1  –  Parameters 

 file,(@file)

 The /COMPRESS , /DUMP and /RECOVER qualifier require a
 directory-file name as a parameter. A logical name or an indirect
 command file can also be used as a parameter eg.: DIR/COMPRESS @DIR.COM .
 Thus it is possible to generate a list with SEARCH device/OUTPUT=file
 and use that file as input to the DIRECTORY command.
 The list generated by DFU SEARCH will contain the device name in
 the file specification. If a filelist is used from another source
 which does not contain the device name, the /DEVICE must be used to
 append the device name to the file.

 device

 The /ALIAS, /EMPTY , /REBUILD_MFD and /VERSION qualifier require
 a device name as a parameter.

2  –  Qualifiers

2.1    /ALIAS 

    Scan all directories on a disk for alias files.

2.2    /COMPRESS 

    Recreates and compresses the directory. Because directories
    are alphabetically sorted files, deleting and entering files
    randomly will create 'holes' in directory files. /COMPRESS
    will remove these holes by rebuilding and truncating the
    directory.

2.3    /DEVICE=device-name 

    Append the device name to the directory-file name. Can only be
    used with /COMPRESS or /DUMP

2.4    /DUMP 

    Produces a dump of the directory file block by block.
    This command may be usefull for debugging corrupted
    or suspected directories.

2.5    /EMPTY 

    Scan the disk for empty directories.

2.6    /FILL_FACTOR 

    /FILL_FACTOR=percentage

    This qualifier is only valid in combination with /COMPRESS.
    Default behaviour for DFU is to compress a directory as tight
    as possible; this is equivalent to /FILL_FACTOR=100.
    By choosing a lower fill_factor DFU will leave some free
    space in each directory block. /FILL_FACTOR may be between
    50 and 100 %. Caution : choosing a fill_factor lower than
    100% may fail if the directory file is not large enough.
    In that case DFU will signal an error and advise using
    a higher fill_factor.

2.7    /FORMAT 

    /FORMAT=format_string

    Used with /VERSION and /OUTPUT. Create an output file using
    the format as described in formatstring. The format string
    MUST contains the !AS directive; DFU fills in the resultant
    file there. Example :

 	DFU> DIR/VERSION=3/OUT=P.COM/FORMAT="$purge !AS"

2.8    /OUTPUT 

    /OUTPUT=filename

    This qualifier redirects the output from DFU to an output file.

2.9    /REBUILD_MFD 

    /REBUILD_MFD

    Rebuilds the disk's 000000.DIR directory and makes sure
    the file backlinks to itself.

2.10    /RECOVER 

    /RECOVER

    Rebuilds a corrupted directory file. Do not use this
    command on critical (system)directories!

2.11    /STATISTICS 

    /STATISTICS
    /NOSTATISTICS  (default)

    Controls whether CPU and I/O consumption of the
    command are shown.

2.12    /TEST 

    This qualifier can be used only in conjunction with /COMPRESS.
    When /TEST is specified DFU will show the results of a
    directory compression without actually performing a compress
    operation.

2.13    /TRUNCATE 

    /TRUNCATE(=n)
    This qualifier is only valid in combination with /COMPRESS.
    After compressing a directory DFU will NOT truncate the
    empty blocks at the end of the directory , unless /TRUNCATE
    is specified. A number 'n' may be specified to let DFU truncate
    no further than 'n' blocks. ('n' will be rounded up to a
    multiple of the disks cluster size.) Example: a 60 block
    directory A.DIR can be compressed to 20 blocks. The results are:

 	DIR/COMPRESS 	            -->  A.DIR size 20/60 blocks.
 	DIR/COMPRESS/TRUNCATE       -->  A.DIR size 20/20 blocks.
 	DIR/COMPRESS/TRUNCATE=40    -->  A.DIR size 20/40 blocks.

2.14    /VERSION 

    /VERSION=n

    Scan all directories of a given device for files which have
    at least 'n' versions.
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