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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 ] [ gpassword ] archive [ file-
       name ...]

DESCRIPTION
       Arc is a general archive and file(1,n) compression utility, used to maintain
       a  compressed  archive of files.  An archive is a single file(1,n) that com-
       bines many files, reducing storage space and allowing multiple files to
       be  handled  as  one.   Arc uses one of several compression methods for
       each file(1,n) 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(3x,7,3x curs_move) files to archive.  Same as 'a' switch(1,n) except that the files are
          deleted from the directory as they are moved to the archive.

       u  update(7,n)  files  in(1,8)  archive.  This switch(1,n) will replace archived files
          when the named(5,8) file(1,n) is newer than the archived copy.  New files will
          be added automatically.

       f  freshen  files  in(1,8)  archive.  Same as 'u' except that new files will
          not be added.

       d  delete files in(1,8) archive.  The named(5,8) files are removed from  the  ar-
          chive.

       x,e
          extract  files from archive.  The named(5,8) files are extracted from the
          archive and created in(1,8) the  current  directory  in(1,8)  an  uncompressed
          state.

       r  run  one  file(1,n) with arguments from archive.  Any program may be exe-
          cuted 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 redi-
          rection. A form-feed is appended after each file(1,n), to ease  use  with
          printers.

       l  list  files  in(1,8)  archive.  Limited information listing of files con-
          tained in(1,8) 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(1,8) archive.  Complete  information  listing
          of  files  contained in(1,8) an archive.  Displays the filename, original
          length, storage method, storage factor(1,6) (% savings), compressed size,
          date, time(1,2,n), 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(1,n)  and
          rename(1,2,n)  to  .BAK.   This  switch(1,n) may be used with the following com-
          mands:  a, m, u, f, d, c.

       i  suppress image mode.  This switch(1,n) 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(1,8) 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(1,n) may be used with the follow-
          ing commands:  a, m, u, f, c.

       w  suppress warning messages.  This switch(1,n) 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(1,n)  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(1,n)  will  make
          existing  files silently get overwritten, instead of asking for con-
          firmation, which is the default.

       q  force Squash compression method.  This switch(1,n) causes the Squash com-
          pression 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(2,n,1 builtins) them.  BE CAREFUL!  This must be the last param-
          eter in(1,8) the switches because everything following  is  part  of  the
          password.

PROGRAMMING NOTES
       Arc  Version 2 differs from version(1,3,5) 1 in(1,8) that archive entries are auto-
       matically compressed when they are added to the archive, making a sepa-
       rate  compression  step  unecessary.   The nature of the compression is
       indicated by the header version(1,3,5) number placed in(1,8) 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(1,7,1 tput)
                9 = Squashing

       Type 5, Lempel-Zev packing, was added as of version(1,3,5) 4.0

       Type  6  is  Lempel-Zev  packing where runs of repeated characters have
       been collapsed, and was added as of version(1,3,5) 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(1,3,5)
       4.6

       Type 8 is a different implementation of Lempel-Zev,  using  a  variable
       code size and an adaptive block reset(1,7,1 tput), and was added as of version(1,3,5) 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(1,8,3 Search::Dict) for environment variables named(5,8) ARCTEMP or TMPDIR, which,
       if(3,n) present, indicates the pathname where temporary files should be cre-
       ated.  This  is typically the location of a RAMdisk on a microcomputer,
       "/tmp/" or left unset.

       See the included documentation file(1,n) for more details.

HISTORY
       Arc has been in(1,8) use in(1,8) the CP/M and MSDOS world for many  years.   Thom
       Henderson  developed  the original version(1,3,5), but it is important to note
       that arc is based on the file(1,n) compression theories developed  by  Huff-
       man(1,5,7),  Welch,  Knott, Knuth, and many other scientists. This implementa-
       tion is based on version(1,3,5) 5.21 of the MSDOS program.

BUGS
       Arc behaves just like the PC version(1,3,5) 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  file-
       names,  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(1,8) a "shar" before arcing them.

       There  shouldn't  be  any  problems, (hah!) but if(3,n) you find any, please
       send(2,n) 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 sup-
       port 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(1L)

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