readme.txt

arj source code

   @PRODUCT_LONG  @{r74}@{d}@{_}


   INTRODUCTION

      To meet  the data  archiving  needs, ARJ Software  Russia delivers a
      range of its own  products based  on the code of  original ARJ. From
      the  beginning,  our  goal  was  to  retain  the  functionality  and
      compatibility with  the  original ARJ  for DOS, but we  also provide
      features  and  enhancements  that  are a  must for certain  tasks or
      certain platforms where no ARJ has been before.


   NEW FEATURES AND DIFFERENCES FROM THE ORIGINAL ARJ

      ("-" indicates a  missing feature, "*" - a different  operation and
       "+" stands for a feature unique for our implementation)

      -  There may be a  significant  performance drawback  when accessing
         files on volumes with no write-back cache.

      *  The "-hm" options  are  compatible  with their ARJ implementation
         hence  a  temporary  swap  file  is  created  if  the  file  list
         exceeds  3000  files.  To keep  the  entire list  in  memory, use
         -hm65000. This  is  useful if you are running  a non-DOS version,
         have  an   adequate  amount  of   RAM  and   therefore   are  not
         constrained with RAM occupied by file lists.

      *  The ARJ display  program, ARJ$DISP, has been  renamed to ARJDISP.
         If you are using a custom  display module, you  have to rename it
         as well.

      +  "ARJ a -d1" will delete  files without asking for  permission, as
         "ARJ m". "ARJ a -d2" will  truncate  files, rather than  deleting
         them, which is usually suggested for keeping hard links.

      +  The "-h#" option  has been  improved to  allow  custom  date/time
         formats.  A  custom  format  is  specified  by  putting a  format
         sequence   right   after  the "-h#".  The  following   characters
         represent date/time macros:

          Y = year,       M = month,      D = day
          h = hour,       m = minute,     s = second
          N = day of year

          (note that these are case-sensitive)

         All  other  characters,  as  well as  those going  beyond  format
         limits (4  digits for year, 2 digits for all  other fields),  are
         treated as delimiters. Examples:

         ARJ a project- -h#YYYYMMDD              (project-19991022.arj)
         ARJ a backup- -h#MM-DD_hh-mm-ss    (backup-10-22_23-57-16.arj)
         ARJ a specs -h#YY                                (specs99.arj)
         ARJ a logs_ -h#NNN                              (logs_295.arj)
         ARJ a test -h#YYYYYYYY                      (testYYYY1999.arj)

      +  The "-ha" has been improved. Now, when  used  in conjuction  with
         an archiving  command, it does  not mark read-only  files as such
         in archive.  This simplifies  archiving from  CD-ROM media  where
         virtualized read-only  attribute  is  forced  by  respective IFS
         driver.

      +  The  "-2a"  option  is  implemented  in  ARJ  due  to  a  popular
         demand from  FidoNet system  operators.  Basically it  acts  like
         "-jo",  with   the   exception  that  file  names,  and  not  the
         extensions,  are  "serialized". Consider  having  a  file  called
         "FILE995N.TXT" and  an archive that contains  the  same  file. If
         extracted  with  the "-2a"  option,  the  file  will  be  written
         to  "FILE9950.TXT", if  you extract it  again,  it'll  be  called
         "FILE9951.TXT",  and   so   on   up   to   "FILE9959.TXT",   then
         "FILE9960.TXT". And  after  "FILE9999.TXT" ARJ  will  start  with
         "FIL00000.TXT". This option allows you  to extract  one  file  to
         100000000  unique  names.  It's  essential  to  system  operators
         since multiple mail  packets with  the same  name may  come  from
         different systems.

         NOTES:
           1. It'll be wise to  include  this  option in the  script  that
              unpacks the ARCmail  packets and  NOT  in ARJ_SW environment
              variable. This  option is  a  security  measure  for systems
              running in  unattended  mode, and  will  only confuse you if
              enabled by default.
           2. There's a security  hole: a file  called  "9999.XXX" or  so,
              will not  be  overwritten.  However, all  subsequent  writes
              will be  redirected  into  file  "0000.XXX". So, files  with
              9s in the beginning have  less  chances of being  preserved.
              Hopefully such situation is unlikely for FidoNet systems.
           3. There is  another  option, "-jo1", to  serialize  filenames,
              however  its   operation   is  different.  The  volume  must
              support  long  filenames  in   order  to  use  this  option,
              moreover,  it's  not   suitable  for  dealing  with  FidoNet
              ARCmail.

      +  "-2d" enforces  the header  compatibility mode. In this mode, the
         archive   header   format   corresponds  to   the   original  ARJ
         specification, besides this, "MS-DOS" is  stamped as the host OS,
         to prevent the "Binary file from a different OS" warning messages
         when unpacking  the archive  in DOS. "-2d1" retains  the enhanced
         header format, but makes the archive comment display correctly in
         DOS.

      +  "-2f" can be  used  to  apply  the archive  comment to the  first
         volume only, and to strip it out for subsequent volumes.

      +  "-2k" option forces 2-digit display of year in lists. This can be
         helpful if the 3-digit  year format used for dates beyond 2100 is
         confusing.

         Alternatively, "-2k1" uses a non-ambigous  format  that  is  both
         easy to read and  information-packed.  The dates are  represented
         by two digits if  the year  is 1970 to 2069, and in three  digits
         if it's 2070 or beyond.

      +  "-2r" tells ARJ to store  directory  attributes first, then store
         its contents. This is the order  that was used  by default in ARJ
         prior to 2.76. It is useful  when the archive is  to be extracted
         in an older version of ARJ to avoid directory  overwrite prompts.
         Upon extraction, it forces ARJ to ask if directory attributes are
         to  be  overwritten (by default, ARJ  will  always overwrite  the
         directory attributes without asking for confirmation).

      +  With no ARJ_SW  specified, ARJ  looks for  a file  named  ARJ.CFG
         in its home  directory. If found, this file  will  be parsed  and
         used  as  a  standard  ARJ  configuration  file (see  manual  for
         details). For UNIX platforms, this  has been changed to search in
         certain standard locations instead of home directory, see the ARJ
         for UNIX notes for further reference.

      +  REARJ v 2.42.05 and higher accepts the "T" modifier in REARJ.CFG,
         which means that it should take care to delete the output archive
         itself if rearchiving fails.


   EXTENDED ATTRIBUTES HANDLING

      Beginning  with  version  2.62.10,  the  extended  attributes  (also
      referenced to  as  EAs) can  be  backed  up  and   restored  without
      needing  any external  utilities. This is  achieved  by  compressing
      and  storing EAs as a part  of file  header. ARJ  supports SAA-style
      EAs under OS/2 and Windows NT.

      Restrictions on EA support:

      *  The multivolume restart  feature (-jn) will not  work  if EAs are
         enabled. You'll  have to  disable EAs  with -2e  prior  to  using
         -jn, or to recreate the archive if the EAs are precious.

      *  Hollow mode archives do not support EAs.

      *  Under Windows NT, extended attributes cannot be overwritten. That
         is, if the EA data is appended to  a file which  already contains
         EAs at the time of unarchiving, the file will retain its original
         EAs.

      A set of new options has been introduced to let  the user control EA
      handling:

      *  "-2c" restricts  EA  handling  to  critical  EAs  only.  Archived
         non-critical  EAs  will not  be  restored.  When  an  archive  is
         created, only critical EAs will be saved.

      *  "-2e" specifies EA inclusion  filter. With no  parameters  given,
         it disables EA  handling at  all. Otherwise, an  expression  that
         follows  it  is  interpreted  as  a   wildcard  that   limits  EA
         inclusion to a  particular EAs. Multiple  options can be  entered
         to represent a set of EA names but list files are not allowed.
         Examples:

         ARJ a test

         In this example, all EAs will be preserved.

         ARJ a no_eas -2e
         ARJ x no_eas -2e

         EAs will neither be packed nor restored.

         ARJ a documents -2e.LONGNAME

         In this case, only .LONGNAME EAs will be handled.

         ARJ a test -2e.CLASSINFO -2e.ICON*

         .CLASSINFO and .ICON* (i.e. .ICON, .ICON1, .ICONPOS) EAs  will be
         be packed and restored.

         It's wise  to specify "-2e.*" when backing up  your OS/2  desktop
         or  configuration  files.  The system  EAs  start with  dot (".")
         while application EAs start with application name.

      *  "-2l" allows to  convert  .LONGNAME  extended  attributes  (these
         represent icon titles used in  WPS) to file names, when possible.
         This feature  simplifies moving document  files away from an OS/2
         system installed on a FAT volume.

         If  the icon  title (and  so  the  extended  attribute)  contains
         line breaks, wildcard characters  or other symbols, real filename
         will be used instead and the .LONGNAME EA will be preserved.

         This option is ignored during extraction. "-2e" and "-2x" have no
         effect  on  this  option  (but  .LONGNAME EAs are  not  saved  if
         .LONGNAME EA handling is implicitly or explicitly disabled).

      *  "-2x" specifies an  exclusion  filter. It must be followed  by an
         exclusion  EA name  specification. The  rules  are  the  same  as
         with "-2e". Also, the  two options  may  work together, providing
         both an inclusion and an exclusion rule. For example:

         ARJ a backup_ -r -p1 -h#2 -2e.* -2x.FED* c:\projects

         may be used to  create  regular back-ups of your  work directory,
         including all system EAs  but  excluding  EAs  created  with FED
         (Fast Editor  Lite, an  editor written  by Sergey I. Yevtushenko,
         [e-mail]) - that program  does not follow traditional
         EA naming  conventions  and  uses  system-alike  EAs  for  anchor
         position marks.

      Extended  attributes are  also  supported in ARJSFXV self-extractors
      where they are stored using the  same  technology as with  usual ARJ
      archives.

      The presence of EAs  is  indicated  by a "(EA: ...)" message when  a
      file is packed. Note that this size  may differ from  the one  given
      when the file  is unpacked - the  former is  the EA  structure  size
      and the latter is the space allocated  for EA storage. The number of
      EAs and the size of EA structure is  also displayed when the archive
      is listed with "ARJ v" command.


   FREQUENTLY ASKED QUESTIONS

      Q: Third-party applications can't handle ARJ for @PLATFORM archives!
      A: Try to disable extended attributes (-2e), DTA/DTC  storage (-j$),
         hard  links  (-2h),  and   enforce  the  DOS  mode  (-2d).   Many
         applications   are  incapable  of  handling  new  archive  format
         (although  this  format is  fully compliant  with the  documented
         guidelines). Known  examples  of such  applications  include File
         Commander v 2.11, Norton Commander v 5.00 and WinRAR v 2.60.

      Q: Extended attribute  sizes reported  by  InfoZIP and  ARJ  differ.
         What's the cause?
      A: As we have  stated earlier, ARJ reports  the size of its internal
         EA storage structure as the  EA size when archiving files. Across
         various platforms   (OS/2-16, OS/2-32, NT)  there are  various EA
         structures.  The system is   questioned for  the  actual  EA size
         during archiving.