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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 [ filename ...]

DESCRIPTION
       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-
       est 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 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'
	  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  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.

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, 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.

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  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.

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; ALL RIGHTS RESERVED

       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.

Howard Chu@JPL				   11 Nov 1991					   ARC(1)
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