ARC

                         File Archive Utility


ARC is used to create and maintain file archives.  An archive is a 
group of files collected together into one file in such a way that the 
individual files may be recovered intact.  

ARC is different from other archive and library utilities in that it 
automatically compresses the files being archived, so that the 
resulting archive takes up a minimum amount of space.  

When ARC is used to add a file to an archive it analyzes the file to 
determine which of four storage methods will result in the greatest 
savings.  These four methods are: 

1)  No compression; the file is stored intact.  

2)  Repeated-character compression; repeated sequences of the same 
    byte value are collapsed into a three-byte code sequence.  

3)  Huffman squeezing; the file is compressed into variable length bit 
    strings, similar to the method used by the SQ programs.  

4)  Lempel-Zev compression;  the file is stored as a series of twelve 
    bit codes which represent character strings, and which are created 
    "on the fly".  

Note that since one of the four methods involves no compression at 
all, the resulting archive entry will never be larger than the 
original file.  



                               USING ARC
                               =========

ARC is invoked with a command of the following format:

    ARC <x> <arcname> [<template> . . .]

Where:

    <x> is an ARC command letter (see below), in either upper or lower 
    case.  

    <arcname> is the name of the archive to act on, with or without an 
    extension.  If no extension is supplied, then ".ARC" is assumed.  
    The archive name may include path and drive specifiers.

    <template> is one or more file name templates.  The "wildcard" 
    characters "*" and "?" may be used.  A file name template may only 
    include a path or drive specifier if you are adding a file to an 
    archive.  

If ARC is invoked with no arguments (by typing "ARC", and pressing 
"enter"), then a brief command summary is displayed.


                             ARC COMMANDS
                             ============

Following is a brief summary of the available ARC commands:

    a,u = add files to archive
    m   = move files to archive
    d   = delete files from archive
    x,e = extract files from archive
    r   = run files from archive
    p   = copy files from archive to stdout
    l   = list files in archive
    v   = verbose listing of files in archive
    t   = test archive integrity
    c   = convert entry to new packing method
    b   = retain backup copy of archive
    w   = suppress warning messages
    n   = suppress notes and comments

These commands are explained in more detail below.



ADDING FILES
------------

Files are added to an archive using the "A" (Add), "U" (Update), or 
"M" (Move) commands.  Add and Update are identical.  Move differs in 
that the source file is deleted once it has been added to the archive.

For example, if you wish to add a file named "TEST.DAT" to an archive 
named "MY.ARC", you would use a command of the form:

    ARC a my test.dat

or:

    ARC u my.arc test.dat

If you wanted to move all files in your current directory into an 
archive named "SUM.ARC", you could use a command of the form:

    ARC m sum *.*

If you wanted to add all files with a ".C" extension, and all files 
named "STUFF" to an archive named "JUNK.ARC", you could type:

    ARC a junk *.c stuff.*

Archive entries are always maintained in alphabetic order.  Archive 
entries may not have duplicate names.  If you add a file to an archive 
that already contains a file by that name, then the existing entry in 
the archive is replaced.  Also, the archive itself and its backup will 
not be added.  

You may also add a file which is in a directory other than your 
current directory.  For example, it is perfectly legal to type:

    ARC a junk c:\dustbin\stuff

The A, U, and M commands are the ONLY commands which allow you to give 
a drive or path.  Also, you cannot add two files with the same name.  
In other words, if you have a file named "C:\DUSTBIN\STUFF.TXT" and 
another file named "C:\BUCKET\STUFF.TXT", then typing:

    arc a junk c:\dustbin\*.* c:\bucket\*.*

will not work.



DELETING FILES
--------------

Archive entries are deleted with the "D" (Delete) command.  For 
example, if you had an archive named "JUNK.ARC", and you wished to 
delete all entries in it with a filename extension of ".C", you could 
type: 

    ARC d junk *.c



EXTRACTING FILES
----------------

Archive entries are extracted with the "E" (Extract) and "X" (eXtract) 
commands.  For example, if you had an archive named "JUNK.ARC", and 
you wanted all files in it with an extension of ".TXT" or ".DOC" to be 
recreated on your disk, you could type:

    ARC x junk *.txt *.doc

If you wanted to extract all of the files in an archive named 
"JUNK.ARC", you could simply type:

    ARC x junk

Whatever method of file compression was used in storing the files is 
reversed, and uncompressed copies are created in the current 
directory.



RUNNING FILES
-------------

Archive entries may be run without being extracted by use of the "R" 
(Run) command.  For example, if you had an archive named "JUNK.ARC" 
which contained a file named "LEMON.COM", which you wished to run, you 
could type:

    ARC r junk lemon.com

You can run any file from an archive which has an extension of ".COM", 
".EXE", or ".BAT".  You cannot run interpretive BASIC programs from an 
archive, nor can you give arguments to a program you are running from 
an archive.

In practice, the file to be run is extracted, run, and then deleted.  
All in all, this is a fairly useless command.



PRINTING FILES
--------------

Archive entries may be examined with the "P" (Print) command.  This 
works the same as the Extract command, except that the files are not 
created on disk.  Instead, the contents of the files are written to 
standard output.  For example, if you wanted to see the contents of 
every ".TXT" file in an archive named "JUNK.ARC", but didn't want them 
saved on disk, you could type:

    ARC p junk *.txt

If you wanted them to be printed on your printer instead of on your 
screen, you could type:

    ARC p junk *.txt >prn



LISTING ARCHIVE ENTRIES
-----------------------

You can obtain a list of the contents of an archive by using the "L" 
(List) command or the "V" (Verbose list) command.  For example, to see 
what is in an archive named "JUNK.ARC", you could type: 

    ARC l junk

If you are only interested in files with an extension of ".DOC", then 
you could type:

    ARC l junk *.doc


ARC prints a short listing of an archive's contents like this:

    Name          Length    Date
    ============  ========  =========
    ALPHA.TXT         6784  16 May 85
    BRAVO.TXT         2432  16 May 85
    COCO.TXT           256  16 May 85


"Name" is simply the name of the file.

"Length" is the unpacked file length.  In other words, it is the 
number of bytes of disk space which the file would take up if it were 
extracted.

"Date" is the date on which the file had last been modified, as of the 
time when it was added to the archive.


ARC prints a verbose listing of an archive's contents like this:

    Name          Length    Stowage    SF   Size now  Date       Time    CRC
    ============  ========  ========  ====  ========  =========  ======  ====
    ALPHA.TXT         6784  Squeezed   35%      4413  16 May 85  11:53a  8708
    BRAVO.TXT         2432  Squeezed   41%      1438  16 May 85  11:53a  5BD6
    COCO.TXT           256   Packed     5%       244  16 May 85  11:53a  3AFB


"Name", "Length", and "Date" are the same as for a short listing.

"Stowage" is the compression method used.  The following compression 
methods are currently employed:

       --          No compression.
     Packed        Runs of repeated byte values are collapsed.
    Squeezed       Huffman squeeze technique employed.
    Crunched       Lempel-Zev compression technique employed.

"SF" is the stowage factor.  In other words, it is the percentage of 
the file length which was saved by compression.

"Size now" is the number of bytes the file is occupying while in the 
archive.

"Time" is the time of last modification, and is associated with the 
date of last modification.

"CRC" is the CRC check value which has been stored with the file.  
Another CRC value will be calculated when the file is extracted or 
tested to ensure data integrity.  There is no especially good reason 
for displaying this value.



BACKUP RETENTION
----------------

When ARC adds or deletes archive entries it renames the original 
archive to give it an extension of ".BAK", and then creates a new 
archive with the desired changes.  If you wish to retain this original 
copy of the archive for backup purposes, then add the "B" (Backup) 
command to your other commands.

For example, if you wanted to delete all entries with an extension of 
".DOC" from an archive named "JUNK.ARC", but you wanted to keep a copy 
around that still has them, then you could type:

    ARC bd junk *.doc

or:

    ARC db junk *.doc



MESSAGE SUPPRESION
------------------

ARC prints two types of messages, warnings and comments.

Warnings are messages about suspected error conditions, such as when a 
file to be extracted already exists, or when an extracted file fails 
the CRC error check.  Warnings may be suppressed by use of the "W" 
(Warn) command.  You should use this command sparingly.  In fact, you 
should probably not use this command at all.

Comments (or notes) are informative messages, such as naming each file 
as it is added to the archive.  Comments and notes may be suppressed 
by use of the "N" (Note) command.

For example, suppose you extracted all files with an extension of 
".BAS" from an archive named "JUNK.ARC"  Then, after making some 
changes which you decide not to keep, you decide that you want to 
extract them all again, but you don't want to be asked to confirm 
every one.  In this case, you could type:

    ARC xw junk *.bas

Or, if you are going to add a hundred files with an extension of 
".MSG" to an archive named "TRASH.ARC", and you don't want ARC to list 
them as it adds them, you could type:

    ARC an trash *.msg

Or, if you want to extract the entire contents of an archive named 
"JUNK.ARC", and you don't want to hear anything, then type:

    ARC xnw junk



TESTING AN ARCHIVE
------------------

The integrity of an archive may be tested by use of the "T" (Test) 
command.  This checks to make sure that all of the file headers are 
properly placed, and that all of the files are in good shape.

This can be very useful for critical archives, where data integrity 
must be assured.  When an archive is tested, all of the entries in the 
archive are unpacked (without saving them anywhere) so that a CRC 
check value may be calculated and compared with the recorded CRC 
value.

For example, if you just received an archive named "JUNK.ARC" over a 
phone line, and you want to make sure that you received it properly, 
you could type:

    ARC t junk

It defeats the purpose of the T command to combine it with N or W.



CONVERTING AN ARCHIVE
---------------------

The "C" (Convert) command is used to convert an archive entry to take 
advantage of newer compression techniques.  For example, if you had an 
archive named "JUNK.ARC", and you wanted to make sure that all files 
with an extension of ".DOC" were encoded using the very latest 
methods, you could type:

    ARC c junk *.doc

Or if you wanted to convert every file in the archive, you could type:

    ARC c junk