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ARC(1L) LOCAL COMMANDS ARC(1L)
NAME
arc - pc archive utility
SYNOPSIS
arc a|m|u|f|d|x|e|r|p|l|v|t|c [ biswnoq ] [ g_p_a_s_s_w_o_r_d ]
_a_r_c_h_i_v_e [ _f_i_l_e_n_a_m_e ...]
DESCRIPTION
_A_r_c is a general archive and file compression utility, used
to maintain a compressed archive of files. An _a_r_c_h_i_v_e is a
single file that combines many files, reducing storage space
and allowing multiple files to be handled as one. _A_r_c uses
one of several compression methods for each file within the
_a_r_c_h_i_v_e, based on whichever method yields the smallest
result.
INSTRUCTIONS
Execute _a_r_c 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 archive.
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 executed directly from the archive. The parame-
ters given after the program name are passed to the pro-
gram without modification.
p copy files from archive to standard output. Useful with
I/O redirection. A form-feed is appended after each file,
to ease use with printers.
Howard Chu@UM Last change: 12 Jun 1988 1
ARC(1L) LOCAL COMMANDS ARC(1L)
l list files in archive. Limited information listing of
files contained 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 informa-
tion 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 commands: 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 deal-
ing 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 following 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 use-
ful 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 existing files silently get overwritten,
instead of asking for confirmation, which is the default.
Howard Chu@UM Last change: 12 Jun 1988 2
ARC(1L) LOCAL COMMANDS ARC(1L)
q force Squash compression method. This switch causes the
Squash compression 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 parameter in the switches because
everything following is part of the password.
PROGRAMMING NOTES
_A_r_c Version 2 differs from version 1 in that archive entries
are automatically compressed when they are added to the
archive, making a separate compression step unecessary. 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 charac-
ters 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.
_A_r_c will look for environment variables named _A_R_C_T_E_M_P or
_T_M_P_D_I_R, which, if present, indicates the pathname where tem-
porary files should be created. This is typically the loca-
tion of a RAMdisk on a microcomputer, "/tmp/" or left unset.
See the included documentation file for more details.
HISTORY
_A_r_c has been in use in the CP/M and MSDOS world for many
years. Thom Henderson developed the original version, but
Howard Chu@UM Last change: 12 Jun 1988 3
ARC(1L) LOCAL COMMANDS ARC(1L)
it is important to note that _a_r_c is based on the file
compression theories developed by Huffman, Welch, Knott,
Knuth, and many other scientists. This implementation is
based on version 5.21 of the MSDOS program.
BUGS
_A_r_c behaves just like the PC version of the program; all
functions of the "usage" display are working. Full compati-
bility with PC ARC files is maintained, the price for which
is that _a_r_c doesn't like long filenames, 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 _a_r_cing them.
There shouldn't be any problems, (hah!) but if you find any,
please send them to me at:
hyc@umix.cc.umich.edu {rutgers, uunet}!umix!hyc
AUTHORS
Original MSDOS program by Thom Henderson
COPYRIGHT(C) 1985-87 by System Enhancement Associates; ALL
RIGHTS RESERVED
Original Lempel-Zev code derived from compress 4.0. Modi-
fied to support Squashing by Dan Lanciani (ddl@harvard.edu)
Ported from MSDOS by Howard Chu (umix!hyc), with help from
John Gilmore (hoptoad!gnu), James Turner (daisy!turner) and
others.
Howard Chu@UM Last change: 12 Jun 1988 4
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