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 ARC(1L)                       Howard Chu@JPL                        ARC(1L)
 LOCAL COMMANDS                                               LOCAL COMMANDS

                                 11 Nov 1991



 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 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,



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 ARC(1L)                       Howard Chu@JPL                        ARC(1L)
 LOCAL COMMANDS                                               LOCAL COMMANDS

                                 11 Nov 1991



         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.




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 ARC(1L)                       Howard Chu@JPL                        ARC(1L)
 LOCAL COMMANDS                                               LOCAL COMMANDS

                                 11 Nov 1991



      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 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 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



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 ARC(1L)                       Howard Chu@JPL                        ARC(1L)
 LOCAL COMMANDS                                               LOCAL COMMANDS

                                 11 Nov 1991



      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.



























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