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                RAR - What's new in the latest version


   Version 5.30

   1. Directory wildcards are allowed in RAR command line in file names to
      archive. For example:

      rar a backup c:\backup\2015*\*

      Recursion is enabled automatically for such directory wildcards
      even if -r switch is not specified.

   2. New 'R' object for -sc switch defines encoding of console
      RAR messages sent to redirected files and pipes. For example:

      rar lb -scur data > list.txt

      will produce Unicode list.txt with archived file names.

   3. Console RAR "l" and "v" commands display file time in YYYY-MM-DD
      format.

   4. "Test" command also verifies contents of NTFS alternate data streams
      in RAR 3.x - 5.x archives. Previously their contents was checked
      only during extraction command.

   5. Bugs fixed:

      a) console RAR crashed instead of displaying an overwrite prompt
         when attempting to add files to already existing volumes;

      b) console RAR "lt" command did not display seconds in file timestamp.

   
   Version 5.21

   1. While previous versions could produce RAR5 volumes of slightly
      smaller than requested size sometimes, such situation is less
      likely now. In most cases volume size equals to specified by user.

   2. Now by default RAR skips symbolic links with absolute paths
      in link target when extracting. You can enable creating such links
      with -ola switch.

      Such links pointing to directories outside of extraction destination
      directory can present a security risk. Enable their extraction only
      if you are sure that archive contents is safe, such as your own backup.

   
   Version 5.20

   1. RAR can read the default set of switches from .rarrc file stored
      in the user's home directory. Previously it was possible to
      define only the same set of switches for all RAR command with
      "switches=<switches>" string. Now .rarrc also allows to specify
      separate switch sets for individual RAR commands using
      the following syntax:

      switches_<command>=<any RAR switches, separated by spaces>

      For example:

      switches_a=-m5 -s
      switches_x=-o+

   2. File overwrite prompt displays the size and modification time
      for existing and new files.

   3. When archiving from stdin with -si switch, RAR sets the current system
      time to modification time of archived file. Previous version did not
      set this time at all.

   4. It is possible to use -si and -v<size> switches together. Previous
      versions did not allow to create volumes when archiving from stdin.

   
   Version 5.11

   1. Timestamp is set to extracted symlinks.

   2. Bugs fixed:

      a) deleting a file in RAR5 solid archive containing files stored
         with -ver switch caused such files to lose version information.

   
   Version 5.10

   1. Switch -ai can be used when creating RAR archive,
      so predefined values, typical for file and directory,
      are stored instead of actual attributes.
      Previously this switch could be used only when extracting.

   
   Version 5.00

   1. New RAR 5.0 archiving format. You can use -ma command line switch
      to create RAR 5.0 archives. By default RAR creates archives
      in 4.x format.

   2. Changes in RAR 5.0 compression algorithm:

      a) maximum compression dictionary size is increased up to 1 GB
         in 64 bit RAR. 32 bit RAR version can use up to 256 MB
         dictionary when creating an archive. Both 32 bit and 64 bit
         versions can unpack archives with any dictionary size,
         including 1 GB;

      b) default dictionary size for RAR 5.0 is 32 MB, typically resulting
         in higher compression ratio and lower speed than RAR 4.x 4 MB.
         You can use -md<size> switch to change this value;

      c) -md<size> switch syntax is modified to support larger dictionary
         sizes. Append 'k', 'm' and 'g' modifiers to specify the size
         in kilo-, mega- and gigabytes, like -md64m for 64 MB dictionary.
         If modifiers are not present, megabytes are assumed,
         so -md64m is equal to -md64;

      d) RAR 5.0 format includes Intel IA-32 executable and delta
         compression algorithms, but RAR 4.x text, audio, true color
         and Itanium algorithms are not supported. These excluded algorithms
         are not efficient for modern data types and hardware configurations;

      e) RAR 5.0 decompression can utilize several CPU cores.
         Though not to same extent as in compression algorithm,
         it improves the decompression speed on large files
         with poorly compressible data or when using BLAKE2 checksums.

   3. Changes in RAR 5.0 archive format:

      a) file times are stored as Coordinated Universal Time (UTC)
         instead of former local time, making file exchange among
         several time zones more straightforward;

      b) file names and archive comments use UTF-8 encoding.
   
   4. RAR 5.0 recovery record is based on Reed-Solomon error correction
      codes. If recovery record size is large enough, 5% and more,
      the new error correction scheme provides much higher resistance to
      multiple damages comparing to RAR 4.x recovery record.
      Smaller record, such as 1 - 2%, or less random damage type would
      result in less difference between 4.x and 5.0. For single continuous
      damage 4.x and 5.0 efficiency is about the same.

      Additionally to usual data erasures, the new recovery record
      is able to detect deletions and insertions of much larger size
      than in previous RAR versions. Maximum insertion size is several
      megabytes. Maximum deletion size depends on the damage type
      and in some cases can be as large as the recovery record size.
      
      Still, the best recovery performance and efficiency is achieved
      if no deletions and insertions are present, so all data including
      damaged sectors preserve their original positions. Thus, if you use
      some special software to copy an archive from damaged media,
      it is better to choose the mode, when damaged sectors are filled by
      zeroes or any other data instead of cutting them out completely
      from resulting file.

      RAR 5.0 recovery record is more resistant to damage of recovery record
      itself and can utilize a partially corrupt recovery record data.
      Note, though, that "Repair" command does not fix broken blocks
      in recovery record. Only file data are corrected. After successful
      archive repair, you may need to create a new recovery record
      for saved files.

      New recovery record is not based on 512 byte sectors anymore 
      and incorporates more complicated data structures. So it is impossible
      to specify its size in sectors. For RAR 5.0 archives the parameter of
      -rr[N] switch and rr[N] command is always treated as a percent of
      archive size regardless of presence of % character. Typically N%
      recovery record can repair up to N% of continuously damaged data
      and increases the archive size by only slightly more than N%.
      Ability to fix multiple damages is proportional to N.

      We used "Screaming Fast Galois Field Arithmetic Using Intel
      SIMD Instructions" paper by James S. Plank, Kevin M. Greenan
      and Ethan L. Miller to improve Reed-Solomon coding performance.
      Also we are grateful to Artem Drobanov and Bulat Ziganshin
      for samples and ideas allowed to make Reed-Solomon coding
      more efficient.

   5. "Test" command verifies validity of RAR 5.0 recovery record.
      Recovery record is tested after processing all archived files.

      If corrupt archive contains the recovery record, it might be possible
      to repair it even if recovery record validity test is failed.
      "Repair" command attempts to utilize even a partially damaged
      recovery record. So treat the negative recovery record test result
      as a reason to re-create the archive if original files are still
      available, but not as a reason to avoid "Repair" command.

   6. Changes in RAR 5.0 encryption algorithm:

      a) encryption algorithm is changed from AES-128 to AES-256 in CBC mode.
         Key derivation function is based on PBKDF2 using HMAC-SHA256;

      b) special password verification value allows to detect most of
         wrong passwords without necessity to unpack the entire file;

      c) if archive headers are not encrypted ("Encrypt file names" option
         is off), file checksums for encrypted RAR 5.0 files are modified
         using a special password dependent algorithm, to make impossible
         guessing file contents based on checksums. Do not expect such
         encrypted file checksums to match usual CRC32 and BLAKE2 values.
   
   7. Switch -htb allows to utilize 256 bit length BLAKE2sp hash
      ( https://blake2.net ) instead of 32 bit CRC32 as a file checksum.

      While producing slightly larger archives, BLAKE2 can be used
      for file contents identification. If two files have the same
      BLAKE2 value, it practically guarantees that file contents
      is the same. BLAKE2 error detection property is also stronger
      than in much shorter CRC32.

   8. Features removed:

      a) authenticity verification feature did not provide the required
         level of reliability and was removed;
      
      b) switch -en (do not add "end of archive" block) is not supported
         by RAR 5.0 archives, which always have the end of archive block.
         This block helps RAR to safely skip external data like
         digital signatures appended to archive;

      c) old style extension based arcname.rNN volume names are not
         supported by RAR 5.0 archives, which use only arcname.partN.rar
         volume names;
      
      d) file comments are not supported anymore both in RAR 4.x
         and RAR 5.0 archives. Console RAR 'cf' command is removed.
         It does not affect the archive comment support, which is present
         in both versions of archive format and is not planned for removal.

   9. Switch -oh stores hard links as link instead of file. It is available
      only for RAR 5.0 archive format.
   
  10. Changes in recovery volume processing in RAR 5.0 archive format:

      a) maximum number of RAR+REV volumes in RAR 5.0 format is 65535
         instead of 255;

      b) recovery volume operations are faster than in RAR 4.x;

      c) additionally to recovery data, RAR 5.0 REV files also store
         service information such as checksums of protected RAR files.
         So they are slightly larger than RAR volumes which they protect.
         If you plan to copy individual RAR and REV files to some removable
         media, you need to take it into account and specify RAR volume
         size by a few kilobytes smaller than media size.
  
  11. Command line RAR returns the exit code 11 if it can detect that
      user entered a wrong password. This code can be returned only
      for RAR 5.0 archives. It is impossible to distinguish a wrong
      password and data damage for RAR 4.x archives.

  12. 'v' and 'l' commands display archived file names in the end of line,
      not in that beginning as before. Also some fields previously
      available in 'l' and 'v' output are now shown only by 'lt' and 'vt'.
      
      'vt' and 'lt' commands provide the detailed multiline information
      for every archived file.

      'vta' and 'lta' also include service headers into list.

   13. UTF-16 little endian encoding is used in RAR log file rar.log,
       so Unicode file names are stored in the log correctly.

       You can use -sc<charset>g switch to change the default log file
       encoding, such as -scag for native single byte encoding.

   14. Command line 'r' (repair) command can include an optional destpath\
       parameter defining the destination folder for repaired archive:

       rar r archive.rar destpath\

   
   Version 4.20

   1. Changes in RAR compression:

      a) Multithreaded RAR compression is enabled by default.
         You can disable it with -mt1 switch.

         Comparing to RAR 4.11, some speed gain is possible
         in single processor mode as well.

         Speed gain depends on data type and average file size.
         Several cores are utilized more efficiently when compressing
         large files.

      b) we had to increase memory requirements to achieve higher
         compression speed. General RAR compression algorithm allocates
         about 120 MB comparing to 40 MB in RAR 4.11;

      c) RAR text compression algorithm cannot utilize several CPU cores
         efficiently, so its performance in multiprocessor environment
         is much lower than for general algorithm. Also its decompression
         speed is much lower than in general algorithm regardless of
         CPU number. So we decided to disable the text algorithm by default.

         If you need maximum possible compression ratio for plain text data
         regardless of speed, you can enable the text compression
         with -mct switch.

   2. RAR general decompression algorithm speed is slightly improved,
      though not to same extent as RAR compression. RAR decompression
      is not able to use several processor cores, so its performance
      does not depend on a number of cores.


   Version 4.11

   1. Bugs fixed:

      a) if -x*\somedir\* exclusion mask was specified when archiving 
         and if name of current directory contained 'somedir', RAR could
         exclude all files and stop creating an archive.


   Version 4.10

   1. Modifications of switch -ag behavior:

      a) -ag can be used with all RAR commands, not just with archiving only;

      b) 'N' format character behavior differs in archiving and non-archiving
         operations. When archiving, it is incremented until the first unused
         name is found. In non-archiving operations like extracting it selects
         the existing archive preceding the first unused name;

      c) 'I' format character allows to specify minutes regardless of presence
         and position of 'H' (hours) in format string. It can be used
         instead of 'M' (minutes), when you wish to place minutes before
         hours or do not need hours at all.

   2. New -log[fmt][=name] switch allows to write archive and file names
      to log file in archiving, extracting, deleting and listing commands.
      This switch is especially useful, when you need to further process
      an archive created with -ag or -v switches, because -log provides
      the archive name generated by RAR.
  
   3. New -@[+] switch allows to process all parameters starting from
      '@' character either as file names (-@) or as file lists (-@+).

   4. Volume size in -v<size> switch can be specified as a decimal fraction.
      Dot (.) is used as the decimal mark. For example, -v1.5g means
      1.5 gigabytes.

   
   Version 4.01

   1. Bugs fixed:

      a) "Repair" command failed to properly reconstruct structure
         of RAR archives, which contained at least one file with packed
         size exceeding 4 GB.

         This bug did not affect the recovery record based repair.
         It happened only if recovery record was not found and RAR
         performed reconstruction of archive structure;

      b) RAR could crash when creating a new archive with -agNNNN switch
         if archive number in generated name was very large,
         like a thousand or more.


   Version 4.00

   1. RAR decompression speed is improved. Depending on data type,
      decompression can be up to 30% faster than in previous versions.

      Both the general RAR algorithm and most of special RAR multimedia
      methods benefit from this improvement. The only module of RAR
      algorithm, which is not affected, is "Text compression" method.
   
   2. Changes in -x<file> switch syntax. Now you can specify a wildcard
      exclusion mask for folders. Such mask must have the trailing '\'
      character, like -x*tmp*\ or -x*\temp\

   3. Recovery volume processing involves less disk seek operations
      resulting in higher performance.

   4. New error code 10 ("no files") is added to list of error codes.
      This new code can be returned by archive, extract, delete
      and repair commands. It means that RAR did not find any files
      matched the specified file or archive mask.