ARC(1) LOCAL COMMANDS ARC(1)
arc - pc archive utility
arc a|m|u|f|d|x|e|r|p|l|v|t|c [ biswnoq ] [ gpassword ] archive [ filename ...]
Arc is a general archive and file compression utility, used to maintain a compressed ar-
chive 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 compres-
sion methods for each file within the archive, based on whichever method yields the small-
Execute arc with no arguments for fairly verbose, usable instructions.
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.
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
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 com-
pares 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'
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 sys-
tems.) 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 compres-
sion). 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 (ana-
lyze, 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 every-
thing following is part of the password.
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, indi-
cates 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.
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 compres-
sion theories developed by Huffman, Welch, Knott, Knuth, and many other scientists. This
implementation is based on version 5.21 of the MSDOS program.
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:
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. Modified to support Squashing by Dan
Lanciani (email@example.com) 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)