NAME¶
arc - pc archive utility
SYNOPSIS¶
arc a|m|u|f|d|x|e|r|p|l|v|t|c [ biswnoq ] [ g
password ]
archive [
filename ...]
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 combines
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
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 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 redirection. A
form-feed is appended after each file, to ease use with printers.
- 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 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 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 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 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 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 existing
files silently get overwritten, instead of asking for confirmation, which
is the default.
- 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¶
Arc 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 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 created. 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 Huffman,
Welch, Knott, Knuth, and many other scientists. This implementation 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
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
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 Public License.
Original Lempel-Zev code derived from compress 4.0. Modified to support
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.