Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
XZ(1)				   XZ Utils				 XZ(1)

NAME
       xz,  unxz,  xzcat, lzma,	unlzma,	lzcat -	Compress or decompress .xz and
       .lzma files

SYNOPSIS
       xz [option]...  [file]...

       unxz is equivalent to xz	--decompress.
       xzcat is	equivalent to xz --decompress --stdout.
       lzma is equivalent to xz	--format=lzma.
       unlzma is equivalent to xz --format=lzma	--decompress.
       lzcat is	equivalent to xz --format=lzma --decompress --stdout.

       When writing scripts that need to decompress files, it  is  recommended
       to  always use the name xz with appropriate arguments (xz -d or xz -dc)
       instead of the names unxz and xzcat.

DESCRIPTION
       xz is a general-purpose data compression	tool with command line	syntax
       similar	to  gzip(1)  and  bzip2(1).  The native	file format is the .xz
       format, but also	the legacy .lzma format	 and  raw  compressed  streams
       with no container format	headers	are supported.

       xz compresses or	decompresses each file according to the	selected oper-
       ation mode.  If no files	are given or file is -,	xz reads from standard
       input and writes	the processed data to standard output.	xz will	refuse
       (display	an error and skip the file) to write compressed	data to	 stan-
       dard output if it is a terminal.	Similarly, xz will refuse to read com-
       pressed data from standard input	if it is a terminal.

       Unless --stdout is specified, files other than -	are written to	a  new
       file whose name is derived from the source file name:

       o  When	compressing,  the  suffix  of  the  target file	format (.xz or
	  .lzma) is appended to	the source filename to get  the	 target	 file-
	  name.

       o  When	decompressing,	the  .xz  or  .lzma suffix is removed from the
	  filename to get the target filename.	xz also	 recognizes  the  suf-
	  fixes	.txz and .tlz, and replaces them with the .tar suffix.

       If  the	target file already exists, an error is	displayed and the file
       is skipped.

       Unless writing to standard output, xz will display a warning  and  skip
       the file	if any of the following	applies:

       o  File	is  not	 a regular file. Symbolic links	are not	followed, thus
	  they are not considered to be	regular	files.

       o  File has more	than one hard link.

       o  File has setuid, setgid, or sticky bit set.

       o  The operation	mode is	set to compress, and the file  already	has  a
	  suffix  of  the  target file format (.xz or .txz when	compressing to
	  the .xz format, and .lzma or .tlz when compressing to	the .lzma for-
	  mat).

       o  The operation	mode is	set to decompress, and the file	doesn't	have a
	  suffix of any	of the supported file formats (.xz,  .txz,  .lzma,  or
	  .tlz).

       After successfully compressing or decompressing the file, xz copies the
       owner, group, permissions, access time, and modification	time from  the
       source file to the target file. If copying the group fails, the permis-
       sions are modified so that the target file doesn't become accessible to
       users who didn't	have permission	to access the source file.  xz doesn't
       support copying other metadata like access control  lists  or  extended
       attributes yet.

       Once  the  target file has been successfully closed, the	source file is
       removed unless --keep was specified. The	source file is	never  removed
       if the output is	written	to standard output.

       Sending	SIGINFO	 or  SIGUSR1 to	the xz process makes it	print progress
       information to standard error.  This has	only limited  use  since  when
       standard	error is a terminal, using --verbose will display an automati-
       cally updating progress indicator.

   Memory usage
       The memory usage	of xz varies from a few	hundred	kilobytes  to  several
       gigabytes depending on the compression settings.	The settings used when
       compressing a file affect also the memory usage	of  the	 decompressor.
       Typically  the decompressor needs only 5	% to 20	% of the amount	of RAM
       that the	compressor needed when creating	the file.  Still,  the	worst-
       case memory usage of the	decompressor is	several	gigabytes.

       To  prevent uncomfortable surprises caused by huge memory usage,	xz has
       a built-in memory usage limiter.	While some operating  systems  provide
       ways  to	 limit	the  memory  usage  of processes, relying on it	wasn't
       deemed to be flexible enough. The default limit depends	on  the	 total
       amount of physical RAM:

       o  If 40	% of RAM is at least 80	MiB, 40	% of RAM is used as the	limit.

       o  If 80	% of RAM is over 80 MiB, 80 MiB	is used	as the limit.

       o  Otherwise 80 % of RAM	is used	as the limit.

       When  compressing, if the selected compression settings exceed the mem-
       ory usage limit,	the settings are automatically adjusted	downwards  and
       a  notice about this is displayed. As an	exception, if the memory usage
       limit is	exceeded when compressing with --format=raw, an	error is  dis-
       played and xz will exit with exit status	1.

       If  source  file	 cannot	 be  decompressed without exceeding the	memory
       usage limit, an error message is	displayed and  the  file  is  skipped.
       Note that compressed files may contain many blocks, which may have been
       compressed with different settings.  Typically  all  blocks  will  have
       roughly	the  same memory requirements, but it is possible that a block
       later in	the file will exceed the memory	 usage	limit,	and  an	 error
       about  too  low	memory	usage limit gets displayed after some data has
       already been decompressed.

       The absolute value of the active	memory usage limit can	be  seen  with
       --info-memory  or  near	the  bottom of the output of --long-help.  The
       default limit can be overridden with --memory=limit.

OPTIONS
   Integer suffixes and	special	values
       In most places where an integer argument	is expected, an	optional  suf-
       fix  is	supported  to easily indicate large integers. There must be no
       space between the integer and the suffix.

       KiB    The integer is multiplied	by 1,024 (2^10). Also Ki,  k,  kB,  K,
	      and KB are accepted as synonyms for KiB.

       MiB    The  integer  is	multiplied by 1,048,576	(2^20).	Also Mi, m, M,
	      and MB are accepted as synonyms for MiB.

       GiB    The integer is multiplied	by 1,073,741,824 (2^30). Also  Gi,  g,
	      G, and GB	are accepted as	synonyms for GiB.

       A  special  value max can be used to indicate the maximum integer value
       supported by the	option.

   Operation mode
       If multiple operation mode  options  are	 given,	 the  last  one	 takes
       effect.

       -z, --compress
	      Compress.	 This  is the default operation	mode when no operation
	      mode option is specified,	and no other operation mode is implied
	      from the command name (for example, unxz implies --decompress).

       -d, --decompress, --uncompress
	      Decompress.

       -t, --test
	      Test the integrity of compressed files.  No files	are created or
	      removed. This option  is	equivalent  to	--decompress  --stdout
	      except  that the decompressed data is discarded instead of being
	      written to standard output.

       -l, --list
	      View information about the  compressed  files.  No  uncompressed
	      output is	produced, and no files are created or removed. In list
	      mode, the	program	cannot read the	compressed data	from  standard
	      input or from other unseekable sources.

	      This feature has not been	implemented yet.

   Operation modifiers
       -k, --keep
	      Keep (don't delete) the input files.

       -f, --force
	      This option has several effects:

	      o	 If the	target file already exists, delete it before compress-
		 ing or	decompressing.

	      o	 Compress or decompress	even if	the input is a	symbolic  link
		 to  a	regular	 file,	has  more  than	 one hard link,	or has
		 setuid, setgid, or sticky bit set.  The setuid,  setgid,  and
		 sticky	bits are not copied to the target file.

	      o	 If  combined with --decompress	--stdout and xz	doesn't	recog-
		 nize the type of the source file, xz  will  copy  the	source
		 file  as  is  to  standard  output.  This  allows using xzcat
		 --force like cat(1) for files that have not  been  compressed
		 with  xz.   Note  that	 in  future, xz	might support new com-
		 pressed file formats, which may make xz decompress more types
		 of  files  instead  of	copying	them as	is to standard output.
		 --format=format can be	used to	restrict xz to decompress only
		 a single file format.

       -c, --stdout, --to-stdout
	      Write  the  compressed  or  decompressed data to standard	output
	      instead of a file. This implies --keep.

       --no-sparse
	      Disable creation of sparse files.	By default,  if	 decompressing
	      into  a  regular	file,  xz tries	to make	the file sparse	if the
	      decompressed data	contains long sequences	of  binary  zeros.  It
	      works  also  when	writing	to standard output as long as standard
	      output is	connected to a regular file,  and  certain  additional
	      conditions  are  met  to make it safe. Creating sparse files may
	      save disk	space and speed	up the decompression by	 reducing  the
	      amount of	disk I/O.

       -S .suf,	--suffix=.suf
	      When  compressing,  use  .suf  as	the suffix for the target file
	      instead of .xz or	.lzma.	If not writing to standard output  and
	      the  source  file	already	has the	suffix .suf, a warning is dis-
	      played and the file is skipped.

	      When decompressing, recognize also files with the	suffix .suf in
	      addition	to files with the .xz, .txz, .lzma, or .tlz suffix. If
	      the source file has the suffix .suf, the suffix  is  removed  to
	      get the target filename.

	      When  compressing	 or  decompressing raw streams (--format=raw),
	      the suffix must always be	specified unless writing  to  standard
	      output, because there is no default suffix for raw streams.

       --files[=file]
	      Read  the	 filenames  to	process	from file; if file is omitted,
	      filenames	are read from standard input. Filenames	must be	termi-
	      nated with the newline character.	A dash (-) is taken as a regu-
	      lar filename; it doesn't mean standard input.  If	filenames  are
	      given  also as command line arguments, they are processed	before
	      the filenames read from file.

       --files0[=file]
	      This is identical	to --files[=file] except  that	the  filenames
	      must be terminated with the null character.

   Basic file format and compression options
       -F format, --format=format
	      Specify the file format to compress or decompress:

	      o	 auto:	This is	the default. When compressing, auto is equiva-
		 lent to xz.  When decompressing, the format of	the input file
		 is  automatically  detected.	Note that raw streams (created
		 with --format=raw) cannot be auto-detected.

	      o	 xz: Compress to the .xz file format, or accept	only .xz files
		 when decompressing.

	      o	 lzma  or  alone: Compress to the legacy .lzma file format, or
		 accept	only .lzma files when decompressing.  The  alternative
		 name  alone is	provided for backwards compatibility with LZMA
		 Utils.

	      o	 raw: Compress or uncompress a raw stream (no  headers).  This
		 is  meant for advanced	users only. To decode raw streams, you
		 need to set not only --format=raw but also specify the	filter
		 chain,	which would normally be	stored in the container	format
		 headers.

       -C check, --check=check
	      Specify the type of the integrity	 check,	 which	is  calculated
	      from  the	uncompressed data. This	option has an effect only when
	      compressing into the .xz format; the .lzma format	 doesn't  sup-
	      port integrity checks.  The integrity check (if any) is verified
	      when the .xz file	is decompressed.

	      Supported	check types:

	      o	 none: Don't calculate an integrity check at all. This is usu-
		 ally  a  bad  idea.  This can be useful when integrity	of the
		 data is verified by other means anyway.

	      o	 crc32:	Calculate CRC32	using the polynomial  from  IEEE-802.3
		 (Ethernet).

	      o	 crc64:	 Calculate  CRC64  using the polynomial	from ECMA-182.
		 This is the default, since it is slightly better  than	 CRC32
		 at detecting damaged files and	the speed difference is	negli-
		 gible.

	      o	 sha256: Calculate SHA-256. This is somewhat slower than CRC32
		 and CRC64.

	      Integrity	 of  the .xz headers is	always verified	with CRC32. It
	      is not possible to change	or disable it.

       -0 ... -9
	      Select compression preset. If a preset level is specified	multi-
	      ple times, the last one takes effect.

	      The  compression	preset	levels can be categorised roughly into
	      three categories:

	      -0 ... -2
		     Fast presets with relatively low memory usage.  -1	and -2
		     should  give  compression	speed and ratios comparable to
		     bzip2 -1 and bzip2	-9, respectively.  Currently -0	is not
		     very  good	 (not  much faster than	-1 but much worse com-
		     pression).	In future, -0 may be indicate some fast	 algo-
		     rithm instead of LZMA2.

	      -3 ... -5
		     Good  compression	ratio with low to medium memory	usage.
		     These are significantly slower than levels	0-2.

	      -6 ... -9
		     Excellent compression with	medium to high	memory	usage.
		     These  are	 also slower than the lower preset levels. The
		     default is	-6.  Unless you	want to	maximize the  compres-
		     sion ratio, you probably don't want a higher preset level
		     than -7 due to speed and memory usage.

	      The exact	compression settings (filter chain) used by each  pre-
	      set  may	vary  between  xz versions. The	settings may also vary
	      between files being compressed, if xz determines	that  modified
	      settings	will  probably	give  better compression ratio without
	      significantly affecting compression time or memory usage.

	      Because the settings may vary, the memory	usage  may  vary  too.
	      The  following table lists the maximum memory usage of each pre-
	      set level, which won't be	exceeded even in  future  versions  of
	      xz.

	      FIXME: The table below is	just a rough idea.

		     Preset   Compression   Decompression
		       -0	  6 MiB		1 MiB
		       -1	  6 MiB		1 MiB
		       -2	 10 MiB		1 MiB
		       -3	 20 MiB		2 MiB
		       -4	 30 MiB		3 MiB
		       -5	 60 MiB		6 MiB
		       -6	100 MiB	       10 MiB
		       -7	200 MiB	       20 MiB
		       -8	400 MiB	       40 MiB
		       -9	800 MiB	       80 MiB

	      When  compressing, xz automatically adjusts the compression set-
	      tings downwards if the memory usage limit	would be exceeded,  so
	      it  is  safe to specify a	high preset level even on systems that
	      don't have lots of RAM.

       --fast and --best
	      These are	somewhat misleading aliases for	 -0  and  -9,  respec-
	      tively.	These  are  provided  only for backwards compatibility
	      with LZMA	Utils.	Avoid using these options.

	      Especially the name of --best is misleading, because the defini-
	      tion  of best depends on the input data, and that	usually	people
	      don't want the very best compression ratio  anyway,  because  it
	      would be very slow.

       -e, --extreme
	      Modify  the  compression preset (-0 ... -9) so that a little bit
	      better compression ratio can be achieved without increasing mem-
	      ory usage	of the compressor or decompressor (exception: compres-
	      sor memory usage may increase a little with presets -0 ...  -2).
	      The downside is that the compression time	will increase dramati-
	      cally (it	can easily double).

       -M limit, --memory=limit
	      Set the memory usage limit. If this option is specified multiple
	      times,  the last one takes effect. The limit can be specified in
	      multiple ways:

	      o	 The limit can be an absolute value in bytes. Using an integer
		 suffix	like MiB can be	useful.	Example: --memory=80MiB

	      o	 The  limit  can be specified as a percentage of physical RAM.
		 Example: --memory=70%

	      o	 The limit can be reset	back to	its default value  by  setting
		 it  to	 0.   See the section Memory usage for how the default
		 limit is defined.

	      o	 The memory usage limiting can be effectively disabled by set-
		 ting limit to max.  This isn't	recommended. It's usually bet-
		 ter to	use, for example, --memory=90%.

	      The current limit	can be seen near the bottom of the  output  of
	      the --long-help option.

       -T threads, --threads=threads
	      Specify the maximum number of worker threads to use. The default
	      is the number of available CPU cores. You	can  see  the  current
	      value  of	 threads near the end of the output of the --long-help
	      option.

	      The actual number	of worker threads can be less than threads  if
	      using  more  threads  would  exceed  the memory usage limit.  In
	      addition to CPU-intensive	worker threads,	xz may use a few  aux-
	      iliary threads, which don't use a	lot of CPU time.

	      Multithreaded  compression and decompression are not implemented
	      yet, so this option has no effect	for now.

   Custom compressor filter chains
       A custom	filter chain allows specifying	the  compression  settings  in
       detail instead of relying on the	settings associated to the preset lev-
       els.  When a custom filter chain	is specified, the  compression	preset
       level options (-0 ... -9	and --extreme) are silently ignored.

       A  filter chain is comparable to	piping on the UN*X command line.  When
       compressing, the	uncompressed input goes	to  the	 first	filter,	 whose
       output  goes to the next	filter (if any). The output of the last	filter
       gets written to the compressed file. The	maximum	number of  filters  in
       the  chain  is  four,  but typically a filter chain has only one	or two
       filters.

       Many filters have limitations where they	can be in  the	filter	chain:
       some  filters  can work only as the last	filter in the chain, some only
       as a non-last filter, and some work  in	any  position  in  the	chain.
       Depending on the	filter,	this limitation	is either inherent to the fil-
       ter design or exists to prevent security	issues.

       A custom	filter chain is	specified by using one or more filter  options
       in the order they are wanted in the filter chain. That is, the order of
       filter options  is  significant!	 When  decoding	 raw  streams  (--for-
       mat=raw),  the  filter  chain  is specified in the same order as	it was
       specified when compressing.

       Filters take filter-specific options as a comma-separated  list.	 Extra
       commas in options are ignored. Every option has a default value,	so you
       need to specify only those you want to change.

       --lzma1[=options], --lzma2[=options]
	      Add LZMA1	or LZMA2 filter	to the filter chain. These filter  can
	      be used only as the last filter in the chain.

	      LZMA1  is	 a legacy filter, which	is supported almost solely due
	      to the legacy .lzma file	format,	 which	supports  only	LZMA1.
	      LZMA2  is	 an  updated  version  of  LZMA1 to fix	some practical
	      issues of	LZMA1. The .xz format uses LZMA2, and doesn't  support
	      LZMA1  at	 all.  Compression speed and ratios of LZMA1 and LZMA2
	      are practically the same.

	      LZMA1 and	LZMA2 share the	same set of options:

	      preset=preset
		     Reset all LZMA1 or	LZMA2 options to preset.  Preset  con-
		     sist  of an integer, which	may be followed	by single-let-
		     ter preset	modifiers. The integer can be  from  0	to  9,
		     matching  the  command  line options -0 ... -9.  The only
		     supported	modifier  is  currently	  e,   which   matches
		     --extreme.

		     The  default  preset  is 6, from which the	default	values
		     for the rest of the LZMA1 or LZMA2	options	are taken.

	      dict=size
		     Dictionary	(history buffer) size indicates	how many bytes
		     of	 the  recently	processed uncompressed data is kept in
		     memory. One method	to reduce  size	 of  the  uncompressed
		     data  is  to  store distance-length pairs,	which indicate
		     what data to repeat from the dictionary buffer. The  big-
		     ger the dictionary, the better the	compression ratio usu-
		     ally is, but dictionaries bigger  than  the  uncompressed
		     data are waste of RAM.

		     Typical  dictionary  size	is  from 64 KiB	to 64 MiB. The
		     minimum is	4 KiB.	The maximum for	 compression  is  cur-
		     rently 1.5	GiB. The decompressor already supports dictio-
		     naries up to one byte less	than 4 GiB, which is the maxi-
		     mum for LZMA1 and LZMA2 stream formats.

		     Dictionary	 size  has  the	 biggest effect	on compression
		     ratio.  Dictionary	size and match finder together	deter-
		     mine  the memory usage of the LZMA1 or LZMA2 encoder. The
		     same dictionary size is required for  decompressing  that
		     was  used	when compressing, thus the memory usage	of the
		     decoder is	determined by the dictionary  size  used  when
		     compressing.

	      lc=lc  Specify  the  number of literal context bits. The minimum
		     is	0 and the maximum is 4;	the default is	3.   In	 addi-
		     tion, the sum of lc and lp	must not exceed	4.

	      lp=lp  Specify  the number of literal position bits. The minimum
		     is	0 and the maximum is 4;	the default is 0.

	      pb=pb  Specify the number	of position bits. The minimum is 0 and
		     the maximum is 4; the default is 2.

	      mode=mode
		     Compression  mode	specifies the function used to analyze
		     the data produced by the match finder.   Supported	 modes
		     are fast and normal.  The default is fast for presets 0-2
		     and normal	for presets 3-9.

	      mf=mf  Match finder has a	major effect on	encoder	speed,	memory
		     usage,  and  compression  ratio. Usually Hash Chain match
		     finders are faster	than Binary Tree match	finders.  Hash
		     Chains  are  usually  used	 together  with	 mode=fast and
		     Binary Trees with mode=normal.  The memory	usage formulas
		     are  only	rough  estimates, which	are closest to reality
		     when dict is a power of two.

		     hc3    Hash Chain with 2- and 3-byte hashing
			    Minimum value for nice: 3
			    Memory usage: dict * 7.5 (if dict <= 16 MiB);
			    dict * 5.5 + 64 MiB	(if dict > 16 MiB)

		     hc4    Hash Chain with 2-,	3-, and	4-byte hashing
			    Minimum value for nice: 4
			    Memory usage: dict * 7.5

		     bt2    Binary Tree	with 2-byte hashing
			    Minimum value for nice: 2
			    Memory usage: dict * 9.5

		     bt3    Binary Tree	with 2-	and 3-byte hashing
			    Minimum value for nice: 3
			    Memory usage: dict * 11.5 (if dict <= 16 MiB);
			    dict * 9.5 + 64 MiB	(if dict > 16 MiB)

		     bt4    Binary Tree	with 2-, 3-, and 4-byte	hashing
			    Minimum value for nice: 4
			    Memory usage: dict * 11.5

	      nice=nice
		     Specify what is considered	to be  a  nice	length	for  a
		     match.  Once a match of at	least nice bytes is found, the
		     algorithm stops looking for possibly better matches.

		     nice can be 2-273 bytes. Higher values tend to give  bet-
		     ter  compression  ratio  at expense of speed. The default
		     depends on	the preset level.

	      depth=depth
		     Specify the maximum search	depth in the match finder. The
		     default  is the special value 0, which makes the compres-
		     sor determine a reasonable	depth from mf and nice.

		     Using very	high values for	depth  can  make  the  encoder
		     extremely	slow with carefully crafted files.  Avoid set-
		     ting the depth over  1000	unless	you  are  prepared  to
		     interrupt the compression in case it is taking too	long.

	      When  decoding  raw streams (--format=raw), LZMA2	needs only the
	      value of dict.  LZMA1 needs also lc, lp, and pb.

       --x86[=options]

       --powerpc[=options]

       --ia64[=options]

       --arm[=options]

       --armthumb[=options]

       --sparc[=options]
	      Add a branch/call/jump (BCJ) filter to the filter	 chain.	 These
	      filters can be used only as non-last filter in the filter	chain.

	      A	 BCJ filter converts relative addresses	in the machine code to
	      their absolute counterparts. This	doesn't	change the size	of the
	      data,  but  it  increases	redundancy, which allows e.g. LZMA2 to
	      get better compression ratio.

	      The BCJ filters are always reversible, so	using a	BCJ filter for
	      wrong  type of data doesn't cause	any data loss. However,	apply-
	      ing a BCJ	filter for wrong type of data is a bad	idea,  because
	      it tends to make the compression ratio worse.

	      Different	instruction sets have have different alignment:

		     Filter	 Alignment   Notes
		     x86	     1	     32-bit and	64-bit x86
		     PowerPC	     4	     Big endian	only
		     ARM	     4	     Little endian only
		     ARM-Thumb	     2	     Little endian only
		     IA-64	    16	     Big or little endian
		     SPARC	     4	     Big or little endian

	      Since  the  BCJ-filtered	data is	usually	compressed with	LZMA2,
	      the compression ratio may	be  improved  slightly	if  the	 LZMA2
	      options  are set to match	the alignment of the selected BCJ fil-
	      ter. For example,	with the IA-64 filter, it's good to  set  pb=4
	      with  LZMA2  (2^4=16). The x86 filter is an exception; it's usu-
	      ally good	to stick to LZMA2's default four-byte  alignment  when
	      compressing x86 executables.

	      All BCJ filters support the same options:

	      start=offset
		     Specify  the  start  offset  that is used when converting
		     between relative and absolute addresses.  The offset must
		     be	a multiple of the alignment of the filter (see the ta-
		     ble above).   The	default	 is  zero.  In	practice,  the
		     default  is  good;	 specifying  a custom offset is	almost
		     never useful.

		     Specifying	a non-zero start  offset  is  probably	useful
		     only  if  the executable has multiple sections, and there
		     are many cross-section jumps or  calls.  Applying	a  BCJ
		     filter separately for each	section	with proper start off-
		     set and then compressing the result as a single chunk may
		     give  some	 improvement  in compression ratio compared to
		     applying the BCJ filter with the default offset  for  the
		     whole executable.

       --delta[=options]
	      Add  Delta  filter  to the filter	chain. The Delta filter	can be
	      used only	as non-last filter in the filter chain.

	      Currently	only simple byte-wise delta calculation	is  supported.
	      It  can  be  useful  when	 compressing  e.g. uncompressed	bitmap
	      images or	uncompressed PCM audio.	However, special purpose algo-
	      rithms may give significantly better results than	Delta +	LZMA2.
	      This is true especially with audio, which	compresses faster  and
	      better e.g. with FLAC.

	      Supported	options:

	      dist=distance
		     Specify  the  distance of the delta calculation as	bytes.
		     distance must be 1-256. The default is 1.

		     For example, with dist=2 and eight-byte input A1 B1 A2 B3
		     A3	B5 A4 B7, the output will be A1	B1 01 02 01 02 01 02.

   Other options
       -q, --quiet
	      Suppress	warnings  and  notices.	Specify	this twice to suppress
	      errors too.  This	option has no effect on	the exit status.  That
	      is,  even	 if a warning was suppressed, the exit status to indi-
	      cate a warning is	still used.

       -v, --verbose
	      Be verbose. If standard error is connected  to  a	 terminal,  xz
	      will  display  a progress	indicator.  Specifying --verbose twice
	      will give	even more verbose output  (useful  mostly  for	debug-
	      ging).

	      The progress indicator shows the following information:

	      o	 Completion  percentage	is shown if the	size of	the input file
		 is known.  That is, percentage	cannot be shown	in pipes.

	      o	 Amount	of compressed data produced (compressing) or  consumed
		 (decompressing).

	      o	 Amount	 of  uncompressed  data	consumed (compressing) or pro-
		 duced (decompressing).

	      o	 Compression ratio, which is calculated	by dividing the	amount
		 of  compressed	 data processed	so far by the amount of	uncom-
		 pressed data processed	so far.

	      o	 Compression or	decompression speed. This is measured  as  the
		 amount	 of  uncompressed  data	consumed (compression) or pro-
		 duced (decompression) per second. It is shown once a few sec-
		 onds have passed since	xz started processing the file.

	      o	 Elapsed  time	or  estimated time remaining.  Elapsed time is
		 displayed in the  format  M:SS	 or  H:MM:SS.	The  estimated
		 remaining  time  is  displayed	in a less precise format which
		 never has colons, for example,	2 min 30 s. The	 estimate  can
		 be  shown only	when the size of the input file	is known and a
		 couple	of seconds have	already	passed since xz	 started  pro-
		 cessing the file.

	      When  standard  error  is	not a terminal,	--verbose will make xz
	      print the	filename, compressed size, uncompressed	size, compres-
	      sion ratio, speed, and elapsed time on a single line to standard
	      error after compressing or decompressing the file. If  operating
	      took at least a few seconds, also	the speed and elapsed time are
	      printed. If the operation	didn't finish, for example due to user
	      interruption,  also  the completion percentage is	printed	if the
	      size of the input	file is	known.

       -Q, --no-warn
	      Don't set	the exit status	to 2 even if a condition worth a warn-
	      ing  was	detected.  This	 option	 doesn't  affect the verbosity
	      level, thus both --quiet and --no-warn have to be	 used  to  not
	      display warnings and to not alter	the exit status.

       --robot
	      Print messages in	a machine-parsable format. This	is intended to
	      ease writing frontends that want to use xz instead  of  liblzma,
	      which may	be the case with various scripts. The output with this
	      option enabled is	meant to be stable across  xz  releases.  Cur-
	      rently  --robot is implemented only for --info-memory and	--ver-
	      sion, but	the idea is to make it usable for  actual  compression
	      and decompression	too.

       --info-memory
	      Display  the current memory usage	limit in human-readable	format
	      on a single line,	and exit successfully. To see how much RAM  xz
	      thinks your system has, use --memory=100%	--info-memory.	To get
	      machine-parsable output (memory usage  limit  as	bytes  without
	      thousand separators), specify --robot before --info-memory.

       -h, --help
	      Display  a  help	message	 describing  the  most	commonly  used
	      options, and exit	successfully.

       -H, --long-help
	      Display a	help message describing	all features of	xz,  and  exit
	      successfully

       -V, --version
	      Display  the  version number of xz and liblzma in	human readable
	      format. To get machine-parsable output, specify  --robot	before
	      --version.

EXIT STATUS
       0      All is good.

       1      An error occurred.

       2      Something	 worth	a  warning  occurred,  but  no	actual	errors
	      occurred.

       Notices (not warnings or	errors)	printed	on standard error don't	affect
       the exit	status.

ENVIRONMENT
       XZ_OPT A	 space-separated  list of options is parsed from XZ_OPT	before
	      parsing the options given	on the command line.  Note  that  only
	      options  are  parsed  from  XZ_OPT; all non-options are silently
	      ignored. Parsing is done with getopt_long(3) which is used  also
	      for the command line arguments.

LZMA UTILS COMPATIBILITY
       The  command  line  syntax  of  xz  is  practically a superset of lzma,
       unlzma, and lzcat as found from LZMA Utils 4.32.x. In most cases, it is
       possible	 to replace LZMA Utils with XZ Utils without breaking existing
       scripts.	There are some incompatibilities though, which	may  sometimes
       cause problems.

   Compression preset levels
       The  numbering  of the compression level	presets	is not identical in xz
       and LZMA	Utils.	The most important difference is how dictionary	 sizes
       are  mapped  to	different presets. Dictionary size is roughly equal to
       the decompressor	memory usage.

	      Level	xz	LZMA Utils
	       -1      64 KiB	  64 KiB
	       -2     512 KiB	   1 MiB
	       -3	1 MiB	 512 KiB
	       -4	2 MiB	   1 MiB
	       -5	4 MiB	   2 MiB
	       -6	8 MiB	   4 MiB
	       -7      16 MiB	   8 MiB
	       -8      32 MiB	  16 MiB
	       -9      64 MiB	  32 MiB

       The dictionary size differences affect the compressor memory usage too,
       but  there  are some other differences between LZMA Utils and XZ	Utils,
       which make the difference even bigger:

	      Level	xz	LZMA Utils 4.32.x
	       -1	2 MiB	       2 MiB
	       -2	5 MiB	      12 MiB
	       -3      13 MiB	      12 MiB
	       -4      25 MiB	      16 MiB
	       -5      48 MiB	      26 MiB
	       -6      94 MiB	      45 MiB
	       -7     186 MiB	      83 MiB
	       -8     370 MiB	     159 MiB
	       -9     674 MiB	     311 MiB

       The default preset level	in LZMA	Utils is -7 while in XZ	 Utils	it  is
       -6, so both use 8 MiB dictionary	by default.

   Streamed vs.	non-streamed .lzma files
       Uncompressed  size  of the file can be stored in	the .lzma header. LZMA
       Utils does that when compressing	regular	files.	The alternative	is  to
       mark that uncompressed size is unknown and use end of payload marker to
       indicate	where the decompressor should  stop.   LZMA  Utils  uses  this
       method  when uncompressed size isn't known, which is the	case for exam-
       ple in pipes.

       xz supports decompressing .lzma files with or without  end  of  payload
       marker,	but  all  .lzma	 files	created	 by xz will use	end of payload
       marker and have uncompressed  size  marked  as  unknown	in  the	 .lzma
       header.	This may be a problem in some (uncommon) situations. For exam-
       ple, a .lzma decompressor in an embedded	device might  work  only  with
       files  that  have known uncompressed size. If you hit this problem, you
       need to use LZMA	Utils or LZMA SDK to create  .lzma  files  with	 known
       uncompressed size.

   Unsupported .lzma files
       The  .lzma format allows	lc values up to	8, and lp values up to 4. LZMA
       Utils can decompress files with any lc and lp, but always creates files
       with  lc=3  and	lp=0.  Creating	files with other lc and	lp is possible
       with xz and with	LZMA SDK.

       The implementation of the LZMA1 filter in liblzma requires that the sum
       of  lc  and  lp	must not exceed	4. Thus, .lzma files which exceed this
       limitation, cannot be decompressed with xz.

       LZMA Utils creates only .lzma files which have dictionary size  of  2^n
       (a  power  of  2), but accepts files with any dictionary	size.  liblzma
       accepts only .lzma files	which have dictionary size of  2^n  or	2^n  +
       2^(n-1).	  This	is  to	decrease  false	positives when detecting .lzma
       files.

       These limitations shouldn't be a	problem	in practice, since practically
       all  .lzma  files  have been compressed with settings that liblzma will
       accept.

   Trailing garbage
       When decompressing, LZMA	Utils silently	ignore	everything  after  the
       first  .lzma stream. In most situations,	this is	a bug. This also means
       that LZMA Utils don't support decompressing concatenated	.lzma files.

       If there	is data	left after the first .lzma stream,  xz	considers  the
       file  to	 be corrupt. This may break obscure scripts which have assumed
       that trailing garbage is	ignored.

NOTES
   Compressed output may vary
       The exact compressed output produced from the same  uncompressed	 input
       file may	vary between XZ	Utils versions even if compression options are
       identical.  This	is because the encoder can be improved (faster or bet-
       ter compression)	without	affecting the file format. The output can vary
       even between different builds of	the same XZ Utils version, if  differ-
       ent build options are used.

       The  above  means that implementing --rsyncable to create rsyncable .xz
       files is	not going to happen without freezing a	part  of  the  encoder
       implementation, which can then be used with --rsyncable.

   Embedded .xz	decompressors
       Embedded	.xz decompressor implementations like XZ Embedded don't	neces-
       sarily support files created with  check	 types	other  than  none  and
       crc32.	Since  the default is --check=crc64, you must use --check=none
       or --check=crc32	when creating files for	embedded systems.

       Outside embedded	systems, all .xz format	decompressors support all  the
       check  types, or	at least are able to decompress	the file without veri-
       fying the integrity check if the	particular check is not	supported.

       XZ Embedded supports BCJ	filters, but only with the default start  off-
       set.

SEE ALSO
       xzdec(1), gzip(1), bzip2(1)

       XZ Utils: <http://tukaani.org/xz/>
       XZ Embedded: <http://tukaani.org/xz/embedded.html>
       LZMA SDK: <http://7-zip.org/sdk.html>

Tukaani				  2010-03-07				 XZ(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | ENVIRONMENT | LZMA UTILS COMPATIBILITY | NOTES | SEE ALSO

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=xz&sektion=1&manpath=FreeBSD+8.1-RELEASE>

home | help