ARC(1) LOCAL COMMANDS ARC(1)
NAME
arc - pc archive utility
SYNOPSIS
arc a|m|u|f|d|x|e|r|p|l|v|t|c [ biswnoq ] [ gpassword ] archive [ file-
name ...]
DESCRIPTION
Arc is a general archive and file compression utility, used to maintain
a compressed archive of files. An archive is a single file that com-
bines many files, reducing storage space and allowing multiple files to
be handled as one. Arc uses one of several compression methods for
each file within the archive, based on whichever method yields the
smallest result.
INSTRUCTIONS
Execute arc with no arguments for fairly verbose, usable instructions.
COMMAND SWITCHES
a add files to archive. Copies the indicated files to the archive.
m move files to archive. Same as 'a' switch except that the files are
deleted from the directory as they are moved to the archive.
u update files in archive. This switch will replace archived files
when the named file is newer than the archived copy. New files will
be added automatically.
f freshen files in archive. Same as 'u' except that new files will
not be added.
d delete files in archive. The named files are removed from the ar-
chive.
x,e
extract files from archive. The named files are extracted from the
archive and created in the current directory in an uncompressed
state.
r run one file with arguments from archive. Any program may be exe-
cuted directly from the archive. The parameters given after the
program name are passed to the program without modification.
p copy files from archive to standard output. Useful with I/O redi-
rection. A form-feed is appended after each file, to ease use with
printers.
l list files in archive. Limited information listing of files con-
tained in an archive. Displays the filename, original length, and
date last modified. If the 'n' option (see below) is used, only the
filename is displayed.
v verbose listing of files in archive. Complete information listing
of files contained in an archive. Displays the filename, original
length, storage method, storage factor (% savings), compressed size,
date, time, and CRC.
t test archive integrity. Computes CRC values for each member of the
archive and compares against the previously saved value.
c convert entry to new packing method. Convert files stored with
older methods to newer methods that are more efficient. Also useful
for files previously archived with the 's' option.
OPTIONS
b retain backup copy of archive. Keep the original archive file and
rename to .BAK. This switch may be used with the following com-
mands: a, m, u, f, d, c.
i suppress image mode. This switch causes files to be treated as text
files, and will translate their end-of-line sequence. (Unix's '\n'
vs. '\r\n' used on many other systems.) The default is to perform
no translation when compressing or extracting files. This option
makes dealing with text files much nicer, though the 'tr' command
can also be used. ('\r' in makefiles and C source code is such a
nuisance...)
s suppress compression. This forces new files to be saved using
Method 2 (no compression). This switch may be used with the follow-
ing commands: a, m, u, f, c.
w suppress warning messages. This switch will keep warning messages
from being displayed which is the default. Most warnings concern
the deletion or existence of files with the same name.
n suppress notes and comments. This switch will keep useful notes
from being displayed which is the default. Most notes indicate what
stage of compression is being run (analyze, compaction, storage).
o overwrite existing files when extracting. This switch will make ex-
isting files silently get overwritten, instead of asking for confir-
mation, which is the default.
q force Squash compression method. This switch causes the Squash com-
pression method to be used, instead of Crunch, which is the default.
g encrypt/decrypt archive entry. This is used to encode files so that
others may not read them. BE CAREFUL! This must be the last param-
eter in the switches because everything following is part of the
password.
PROGRAMMING NOTES
Arc Version 2 differs from version 1 in that archive entries are auto-
matically compressed when they are added to the archive, making a sepa-
rate compression step unnecessary. The nature of the compression is
indicated by the header version number placed in each archive entry, as
follows:
1 = Old style, no compression
2 = New style, no compression
3 = Compression of repeated characters only
4 = Compression of repeated characters plus Huffman SQueezing
5 = Lempel-Zev packing of repeated strings (old style)
6 = Lempel-Zev packing of repeated strings (new style)
7 = Lempel-Zev Williams packing with improved hash function
8 = Dynamic Lempel-Zev packing with adaptive reset
9 = Squashing
Type 5, Lempel-Zev packing, was added as of version 4.0
Type 6 is Lempel-Zev packing where runs of repeated characters have
been collapsed, and was added as of version 4.1
Type 7 is a variation of Lempel-Zev using a different hash function
which yields speed improvements of 20-25%, and was added as of version
4.6
Type 8 is a different implementation of Lempel-Zev, using a variable
code size and an adaptive block reset, and was added as of version 5.0
Type 9 is another variation of Lempel-Zev, using a larger hash table.
This method was developed by Phil Katz, and is not supported by the
"official" ARC programs.
Arc will look for environment variables named ARCTEMP or TMPDIR, which,
if present, indicates the pathname where temporary files should be cre-
ated. This is typically the location of a RAMdisk on a microcomputer,
"/tmp/" or left unset.
See the included documentation file for more details.
HISTORY
Arc has been in use in the CP/M and MSDOS world for many years. Thom
Henderson developed the original version, but it is important to note
that arc is based on the file compression theories developed by Huff-
man, Welch, Knott, Knuth, and many other scientists. This implementa-
tion is based on version 5.21 of the MSDOS program.
BUGS
Arc behaves just like the PC version of the program; all functions of
the "usage" display are working. Full compatibility with PC ARC files
is maintained, the price for which is that arc doesn't like long file-
names, and can only archive files with names of up to 12 characters.
It will *sometimes* do The Right Thing with them, but I suggest you put
long-winded filenames in a "shar" before arcing them.
There shouldn't be any problems, (hah!) but if you find any, please
send them to me at:
hyc@hanauma.jpl.nasa.gov
AUTHORS
Original MSDOS program by Thom Henderson
COPYRIGHT(C) 1985-87 by System Enhancement Associates. You may copy
and distribute this program freely, under the terms of the General Pub-
lic License.
Original Lempel-Zev code derived from compress 4.0. Modified to sup-
port Squashing by Dan Lanciani (ddl@harvard.edu) Ported from MSDOS by
Howard Chu, with help from John Gilmore (hoptoad!gnu), James Turner
(daisy!turner) and others.
Howard Chu@JPL 11 Nov 1991 ARC(1)
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