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authorKarl Berry <karl@freefriends.org>2011-04-03 23:53:28 +0000
committerKarl Berry <karl@freefriends.org>2011-04-03 23:53:28 +0000
commit1e665e264ead3dedcf83afc950c43a6764a79884 (patch)
treef2de017feac2b53a9fc3c15b31d9dba1541a7837 /Build/source/extra/xz/doc/man
parent7566b1e9fc57db87642f5e344164e5bbfe209b50 (diff)
xz 5.0.2, from http://tukaani.org/xz/xz-5.0.2.tar.xz
git-svn-id: svn://tug.org/texlive/trunk@21944 c570f23f-e606-0410-a88d-b1316a301751
Diffstat (limited to 'Build/source/extra/xz/doc/man')
-rw-r--r--Build/source/extra/xz/doc/man/pdf-a4/lzmainfo-a4.pdfbin4318 -> 4416 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-a4/xz-a4.pdfbin49793 -> 73968 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-a4/xzdec-a4.pdfbin6900 -> 6668 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-a4/xzdiff-a4.pdfbin4241 -> 4300 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-a4/xzgrep-a4.pdfbin4443 -> 4486 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-a4/xzless-a4.pdfbin4274 -> 4395 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-a4/xzmore-a4.pdfbin4212 -> 4272 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-letter/lzmainfo-letter.pdfbin4316 -> 4407 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-letter/xz-letter.pdfbin49760 -> 75192 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-letter/xzdec-letter.pdfbin6895 -> 6658 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-letter/xzdiff-letter.pdfbin4241 -> 4331 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-letter/xzgrep-letter.pdfbin4440 -> 4506 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-letter/xzless-letter.pdfbin4273 -> 4382 bytes
-rw-r--r--Build/source/extra/xz/doc/man/pdf-letter/xzmore-letter.pdfbin4210 -> 4276 bytes
-rw-r--r--Build/source/extra/xz/doc/man/txt/lzmainfo.txt16
-rw-r--r--Build/source/extra/xz/doc/man/txt/xz.txt1418
-rw-r--r--Build/source/extra/xz/doc/man/txt/xzdec.txt41
-rw-r--r--Build/source/extra/xz/doc/man/txt/xzdiff.txt14
-rw-r--r--Build/source/extra/xz/doc/man/txt/xzgrep.txt8
-rw-r--r--Build/source/extra/xz/doc/man/txt/xzless.txt2
-rw-r--r--Build/source/extra/xz/doc/man/txt/xzmore.txt2
21 files changed, 886 insertions, 615 deletions
diff --git a/Build/source/extra/xz/doc/man/pdf-a4/lzmainfo-a4.pdf b/Build/source/extra/xz/doc/man/pdf-a4/lzmainfo-a4.pdf
index 997898861a2..c2880f37901 100644
--- a/Build/source/extra/xz/doc/man/pdf-a4/lzmainfo-a4.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-a4/lzmainfo-a4.pdf
Binary files differ
diff --git a/Build/source/extra/xz/doc/man/pdf-a4/xz-a4.pdf b/Build/source/extra/xz/doc/man/pdf-a4/xz-a4.pdf
index b893db2b190..f57b03cbf8a 100644
--- a/Build/source/extra/xz/doc/man/pdf-a4/xz-a4.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-a4/xz-a4.pdf
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diff --git a/Build/source/extra/xz/doc/man/pdf-a4/xzdec-a4.pdf b/Build/source/extra/xz/doc/man/pdf-a4/xzdec-a4.pdf
index f79f6076132..5ce079b3ce1 100644
--- a/Build/source/extra/xz/doc/man/pdf-a4/xzdec-a4.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-a4/xzdec-a4.pdf
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diff --git a/Build/source/extra/xz/doc/man/pdf-a4/xzdiff-a4.pdf b/Build/source/extra/xz/doc/man/pdf-a4/xzdiff-a4.pdf
index f6c3a7ca0dc..5c4558a3ed1 100644
--- a/Build/source/extra/xz/doc/man/pdf-a4/xzdiff-a4.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-a4/xzdiff-a4.pdf
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diff --git a/Build/source/extra/xz/doc/man/pdf-a4/xzgrep-a4.pdf b/Build/source/extra/xz/doc/man/pdf-a4/xzgrep-a4.pdf
index 7408a58d466..0fcf79c0586 100644
--- a/Build/source/extra/xz/doc/man/pdf-a4/xzgrep-a4.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-a4/xzgrep-a4.pdf
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diff --git a/Build/source/extra/xz/doc/man/pdf-a4/xzless-a4.pdf b/Build/source/extra/xz/doc/man/pdf-a4/xzless-a4.pdf
index 96af27715c1..1df408e71f1 100644
--- a/Build/source/extra/xz/doc/man/pdf-a4/xzless-a4.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-a4/xzless-a4.pdf
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diff --git a/Build/source/extra/xz/doc/man/pdf-a4/xzmore-a4.pdf b/Build/source/extra/xz/doc/man/pdf-a4/xzmore-a4.pdf
index de444b8e9a1..2655bdf7073 100644
--- a/Build/source/extra/xz/doc/man/pdf-a4/xzmore-a4.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-a4/xzmore-a4.pdf
Binary files differ
diff --git a/Build/source/extra/xz/doc/man/pdf-letter/lzmainfo-letter.pdf b/Build/source/extra/xz/doc/man/pdf-letter/lzmainfo-letter.pdf
index 513b8c03fbb..bde50e13a29 100644
--- a/Build/source/extra/xz/doc/man/pdf-letter/lzmainfo-letter.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-letter/lzmainfo-letter.pdf
Binary files differ
diff --git a/Build/source/extra/xz/doc/man/pdf-letter/xz-letter.pdf b/Build/source/extra/xz/doc/man/pdf-letter/xz-letter.pdf
index 330f6f1d710..3c5fd40503e 100644
--- a/Build/source/extra/xz/doc/man/pdf-letter/xz-letter.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-letter/xz-letter.pdf
Binary files differ
diff --git a/Build/source/extra/xz/doc/man/pdf-letter/xzdec-letter.pdf b/Build/source/extra/xz/doc/man/pdf-letter/xzdec-letter.pdf
index 8476663bcc2..d2cc85daa1d 100644
--- a/Build/source/extra/xz/doc/man/pdf-letter/xzdec-letter.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-letter/xzdec-letter.pdf
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index 2955ec38ae0..9f3011b9a5e 100644
--- a/Build/source/extra/xz/doc/man/pdf-letter/xzdiff-letter.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-letter/xzdiff-letter.pdf
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index 494101e7da2..5d976c12e78 100644
--- a/Build/source/extra/xz/doc/man/pdf-letter/xzgrep-letter.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-letter/xzgrep-letter.pdf
Binary files differ
diff --git a/Build/source/extra/xz/doc/man/pdf-letter/xzless-letter.pdf b/Build/source/extra/xz/doc/man/pdf-letter/xzless-letter.pdf
index 02324f6f13c..da7e166bda2 100644
--- a/Build/source/extra/xz/doc/man/pdf-letter/xzless-letter.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-letter/xzless-letter.pdf
Binary files differ
diff --git a/Build/source/extra/xz/doc/man/pdf-letter/xzmore-letter.pdf b/Build/source/extra/xz/doc/man/pdf-letter/xzmore-letter.pdf
index 3bd45d57eea..720fc299a61 100644
--- a/Build/source/extra/xz/doc/man/pdf-letter/xzmore-letter.pdf
+++ b/Build/source/extra/xz/doc/man/pdf-letter/xzmore-letter.pdf
Binary files differ
diff --git a/Build/source/extra/xz/doc/man/txt/lzmainfo.txt b/Build/source/extra/xz/doc/man/txt/lzmainfo.txt
index 28b1f962f58..2af7801ad21 100644
--- a/Build/source/extra/xz/doc/man/txt/lzmainfo.txt
+++ b/Build/source/extra/xz/doc/man/txt/lzmainfo.txt
@@ -3,22 +3,22 @@ LZMAINFO(1) XZ Utils LZMAINFO(1)
NAME
- lzmainfo - show infomation stored in the .lzma file header
+ lzmainfo - show information stored in the .lzma file header
SYNOPSIS
lzmainfo [--help] [--version] [file]...
DESCRIPTION
- lzmainfo shows information stored in the .lzma file header. It reads
+ lzmainfo shows information stored in the .lzma file header. It reads
the first 13 bytes from the specified file, decodes the header, and
- prints it to standard output in human readable format. If no files are
+ prints it to standard output in human readable format. If no files are
given or file is -, standard input is read.
Usually the most interesting information is the uncompressed size and
- the dictionary size. Uncompressed size can be shown only if the file is
- in the non-streamed .lzma format variant. The amount of memory required
- to decompress the file is a few dozen kilobytes plus the dictionary
- size.
+ the dictionary size. Uncompressed size can be shown only if the file
+ is in the non-streamed .lzma format variant. The amount of memory
+ required to decompress the file is a few dozen kilobytes plus the dic-
+ tionary size.
lzmainfo is included in XZ Utils primarily for backward compatibility
with LZMA Utils.
@@ -37,4 +37,4 @@ SEE ALSO
-Tukaani 2009-08-13 LZMAINFO(1)
+Tukaani 2010-09-27 LZMAINFO(1)
diff --git a/Build/source/extra/xz/doc/man/txt/xz.txt b/Build/source/extra/xz/doc/man/txt/xz.txt
index 5e71d7cca45..bb5ffcf0473 100644
--- a/Build/source/extra/xz/doc/man/txt/xz.txt
+++ b/Build/source/extra/xz/doc/man/txt/xz.txt
@@ -22,15 +22,15 @@ SYNOPSIS
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.
+ format, but the legacy .lzma format used by LZMA Utils and raw com-
+ pressed streams with no container format headers are also 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.
+ dard output if it is a terminal. Similarly, xz will refuse to read
+ compressed 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:
@@ -49,32 +49,32 @@ DESCRIPTION
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 is not a regular file. Symbolic links are not followed, and
+ 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
+ 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
+ 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.
+ source file to the target file. If copying the group fails, the per-
+ missions 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
+ 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
@@ -84,52 +84,50 @@ DESCRIPTION
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.
+ gigabytes depending on the compression settings. The settings used
+ when compressing a file determine the memory requirements of the decom-
+ pressor. Typically the decompressor needs 5 % to 20 % of the amount of
+ memory that the compressor needed when creating the file. For example,
+ decompressing a file created with xz -9 currently requires 65 MiB of
+ memory. Still, it is possible to have .xz files that require several
+ gigabytes of memory to decompress.
+
+ Especially users of older systems may find the possibility of very
+ large memory usage annoying. To prevent uncomfortable surprises, xz
+ has a built-in memory usage limiter, which is disabled by default.
+ While some operating systems provide ways to limit the memory usage of
+ processes, relying on it wasn't deemed to be flexible enough (e.g.
+ using ulimit(1) to limit virtual memory tends to cripple mmap(2)).
+
+ The memory usage limiter can be enabled with the command line option
+ --memlimit=limit. Often it is more convenient to enable the limiter by
+ default by setting the environment variable XZ_DEFAULTS, e.g.
+ XZ_DEFAULTS=--memlimit=150MiB. It is possible to set the limits sepa-
+ rately for compression and decompression by using --memlimit-com-
+ press=limit and --memlimit-decompress=limit. Using these two options
+ outside XZ_DEFAULTS is rarely useful because a single run of xz cannot
+ do both compression and decompression and --memlimit=limit (or -M
+ limit) is shorter to type on the command line.
+
+ If the specified memory usage limit is exceeded when decompressing, xz
+ will display an error and decompressing the file will fail. If the
+ limit is exceeded when compressing, xz will try to scale the settings
+ down so that the limit is no longer exceeded (except when using --for-
+ mat=raw or --no-adjust). This way the operation won't fail unless the
+ limit is very small. The scaling of the settings is done in steps that
+ don't match the compression level presets, e.g. if the limit is only
+ slightly less than the amount required for xz -9, the settings will be
+ scaled down only a little, not all the way down to xz -8.
Concatenation and padding with .xz files
It is possible to concatenate .xz files as is. xz will decompress such
files as if they were a single .xz file.
- It is possible to insert padding between the concenated parts or after
- the last part. The padding must be null bytes and the size of the pad-
- ding must be a multiple of four bytes. This can be useful if the .xz
- file is stored on a medium that stores file sizes e.g. as 512-byte
- blocks.
+ It is possible to insert padding between the concatenated parts or
+ after the last part. The padding must consist of null bytes and the
+ size of the padding must be a multiple of four bytes. This can be use-
+ ful e.g. if the .xz file is stored on a medium that measures file sizes
+ in 512-byte blocks.
Concatenation and padding are not allowed with .lzma files or raw
streams.
@@ -137,19 +135,19 @@ DESCRIPTION
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
+ 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.
+ KiB Multiply the integer by 1,024 (2^10). 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.
+ MiB Multiply the integer by 1,048,576 (2^20). 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.
+ GiB Multiply the integer by 1,073,741,824 (2^30). Gi, g, G, and GB
+ are accepted as synonyms for GiB.
- A special value max can be used to indicate the maximum integer value
+ The special value max can be used to indicate the maximum integer value
supported by the option.
Operation mode
@@ -157,40 +155,40 @@ OPTIONS
effect.
-z, --compress
- Compress. This is the default operation mode when no operation
- mode option is specified, and no other operation mode is implied
+ 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.
+ Test the integrity of compressed files. This option is equiva-
+ lent to --decompress --stdout except that the decompressed data
+ is discarded instead of being written to standard output. No
+ files are created or removed.
-l, --list
- List information about 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.
+ Print information about compressed files. No uncompressed out-
+ put 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.
The default listing shows basic information about files, one
- file per line. To get more detailed information, use also the
- --verbose option. For even more information, use --verbose
- twice, but note that it may be slow, because getting all the
- extra information requires many seeks. The width of verbose out-
- put exceeds 80 characters, so piping the output to e.g. less -S
- may be convenient if the terminal isn't wide enough.
+ file per line. To get more detailed information, use also the
+ --verbose option. For even more information, use --verbose
+ twice, but note that this may be slow, because getting all the
+ extra information requires many seeks. The width of verbose
+ output exceeds 80 characters, so piping the output to e.g.
+ less -S may be convenient if the terminal isn't wide enough.
The exact output may vary between xz versions and different
- locales. To get machine-readable output, --robot --list should
- be used.
+ locales. For machine-readable output, --robot --list should be
+ used.
Operation modifiers
-k, --keep
- Keep (don't delete) the input files.
+ Don't delete the input files.
-f, --force
This option has several effects:
@@ -199,31 +197,31 @@ OPTIONS
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
+ to a regular file, has more than one hard link, or has the
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.
+ o When used with --decompress --stdout and xz cannot recognize
+ the type of the source file, copy the source file as is to
+ standard output. This allows xzcat --force to be used like
+ cat(1) for files that have not been compressed with xz. Note
+ that in future, xz might support new compressed 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 for-
+ mat.
-c, --stdout, --to-stdout
Write the compressed or decompressed data to standard output
- instead of a file. This implies --keep.
+ instead of a file. This implies --keep.
--no-sparse
- Disable creation of sparse files. By default, if decompressing
+ 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
+ decompressed data contains long sequences of binary zeros. It
+ also works 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.
@@ -233,8 +231,8 @@ OPTIONS
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
+ When decompressing, recognize 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.
@@ -244,285 +242,407 @@ OPTIONS
--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.
+ filenames are read from standard input. Filenames must be ter-
+ minated with the newline character. A dash (-) is taken as a
+ regular 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
+ This is identical to --files[=file] except that each filename
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.
+ 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.
+ 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.
+ lzma, 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.
+ raw Compress or uncompress a raw stream (no headers). This
+ is meant for advanced users only. To decode raw streams,
+ you need use --format=raw and explicitly specify the fil-
+ ter chain, which normally would have been stored in the
+ container 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.
+ Specify the type of the integrity check. The check is calcu-
+ lated from the uncompressed data and stored in the .xz file.
+ This option has an effect only when compressing into the .xz
+ format; the .lzma format doesn't support integrity checks. The
+ integrity check (if any) is verified when the .xz file is decom-
+ pressed.
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.
+ 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).
+ 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.
+ 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 neg-
+ ligible.
- o sha256: Calculate SHA-256. This is somewhat slower than CRC32
- and CRC64.
+ sha256 Calculate SHA-256. This is somewhat slower than CRC32
+ and CRC64.
- Integrity of the .xz headers is always verified with CRC32. It
+ 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.
+ Select a compression preset level. The default is -6. If mul-
+ tiple preset levels are specified, the last one takes effect.
+ If a custom filter chain was already specified, setting a com-
+ pression preset level clears the custom filter chain.
+
+ The differences between the presets are more significant than
+ with gzip(1) and bzip2(1). The selected compression settings
+ determine the memory requirements of the decompressor, thus
+ using a too high preset level might make it painful to decom-
+ press the file on an old system with little RAM. Specifically,
+ it's not a good idea to blindly use -9 for everything like it
+ often is with gzip(1) and bzip2(1).
+
+ -0 ... -3
+ These are somewhat fast presets. -0 is sometimes faster
+ than gzip -9 while compressing much better. The higher
+ ones often have speed comparable to bzip2(1) with compa-
+ rable or better compression ratio, although the results
+ depend a lot on the type of data being compressed.
+
+ -4 ... -6
+ Good to very good compression while keeping decompressor
+ memory usage reasonable even for old systems. -6 is the
+ default, which is usually a good choice e.g. for dis-
+ tributing files that need to be decompressible even on
+ systems with only 16 MiB RAM. (-5e or -6e may be worth
+ considering too. See --extreme.)
+
+ -7 ... -9
+ These are like -6 but with higher compressor and decom-
+ pressor memory requirements. These are useful only when
+ compressing files bigger than 8 MiB, 16 MiB, and 32 MiB,
+ respectively.
+
+ On the same hardware, the decompression speed is approximately a
+ constant number of bytes of compressed data per second. In
+ other words, the better the compression, the faster the decom-
+ pression will usually be. This also means that the amount of
+ uncompressed output produced per second can vary a lot.
+
+ The following table summarises the features of the presets:
+
+ Preset DictSize CompCPU CompMem DecMem
+ -0 256 KiB 0 3 MiB 1 MiB
+ -1 1 MiB 1 9 MiB 2 MiB
+ -2 2 MiB 2 17 MiB 3 MiB
+ -3 4 MiB 3 32 MiB 5 MiB
+ -4 4 MiB 4 48 MiB 5 MiB
+ -5 8 MiB 5 94 MiB 9 MiB
+ -6 8 MiB 6 94 MiB 9 MiB
+ -7 16 MiB 6 186 MiB 17 MiB
+ -8 32 MiB 6 370 MiB 33 MiB
+ -9 64 MiB 6 674 MiB 65 MiB
+
+ Column descriptions:
+
+ o DictSize is the LZMA2 dictionary size. It is waste of memory
+ to use a dictionary bigger than the size of the uncompressed
+ file. This is why it is good to avoid using the presets -7
+ ... -9 when there's no real need for them. At -6 and lower,
+ the amount of memory wasted is usually low enough to not mat-
+ ter.
+
+ o CompCPU is a simplified representation of the LZMA2 settings
+ that affect compression speed. The dictionary size affects
+ speed too, so while CompCPU is the same for levels -6 ... -9,
+ higher levels still tend to be a little slower. To get even
+ slower and thus possibly better compression, see --extreme.
+
+ o CompMem contains the compressor memory requirements in the
+ single-threaded mode. It may vary slightly between xz ver-
+ sions. Memory requirements of some of the future multi-
+ threaded modes may be dramatically higher than that of the
+ single-threaded mode.
+
+ o DecMem contains the decompressor memory requirements. That
+ is, the compression settings determine the memory require-
+ ments of the decompressor. The exact decompressor memory
+ usage is slighly more than the LZMA2 dictionary size, but the
+ values in the table have been rounded up to the next full
+ MiB.
-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).
+ Use a slower variant of the selected compression preset level
+ (-0 ... -9) to hopefully get a little bit better compression
+ ratio, but with bad luck this can also make it worse. Decom-
+ pressor memory usage is not affected, but compressor memory
+ usage increases a little at preset levels -0 ... -3.
+
+ Since there are two presets with dictionary sizes 4 MiB and
+ 8 MiB, the presets -3e and -5e use slightly faster settings
+ (lower CompCPU) than -4e and -6e, respectively. That way no two
+ presets are identical.
+
+ Preset DictSize CompCPU CompMem DecMem
+ -0e 256 KiB 8 4 MiB 1 MiB
+ -1e 1 MiB 8 13 MiB 2 MiB
+ -2e 2 MiB 8 25 MiB 3 MiB
+ -3e 4 MiB 7 48 MiB 5 MiB
+ -4e 4 MiB 8 48 MiB 5 MiB
+ -5e 8 MiB 7 94 MiB 9 MiB
+ -6e 8 MiB 8 94 MiB 9 MiB
+ -7e 16 MiB 8 186 MiB 17 MiB
+ -8e 32 MiB 8 370 MiB 33 MiB
+ -9e 64 MiB 8 674 MiB 65 MiB
+
+ For example, there are a total of four presets that use 8 MiB
+ dictionary, whose order from the fastest to the slowest is -5,
+ -6, -5e, and -6e.
+
+ --fast
+ --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.
- -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:
+ --memlimit-compress=limit
+ Set a memory usage limit for compression. If this option is
+ specified multiple times, the last one takes effect.
- o The limit can be an absolute value in bytes. Using an integer
- suffix like MiB can be useful. Example: --memory=80MiB
+ If the compression settings exceed the limit, xz will adjust the
+ settings downwards so that the limit is no longer exceeded and
+ display a notice that automatic adjustment was done. Such
+ adjustments are not made when compressing with --format=raw or
+ if --no-adjust has been specified. In those cases, an error is
+ displayed and xz will exit with exit status 1.
- o The limit can be specified as a percentage of physical RAM.
- Example: --memory=70%
+ The limit can be specified in multiple ways:
- 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 limit can be an absolute value in bytes. Using an inte-
+ ger suffix like MiB can be useful. Example: --memlimit-com-
+ press=80MiB
- 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%.
+ o The limit can be specified as a percentage of total physical
+ memory (RAM). This can be useful especially when setting the
+ XZ_DEFAULTS environment variable in a shell initialization
+ script that is shared between different computers. That way
+ the limit is automatically bigger on systems with more mem-
+ ory. Example: --memlimit-compress=70%
- The current limit can be seen near the bottom of the output of
- the --long-help option.
+ o The limit can be reset back to its default value by setting
+ it to 0. This is currently equivalent to setting the limit
+ to max (no memory usage limit). Once multithreading support
+ has been implemented, there may be a difference between 0 and
+ max for the multithreaded case, so it is recommended to use 0
+ instead of max until the details have been decided.
+
+ See also the section Memory usage.
+
+ --memlimit-decompress=limit
+ Set a memory usage limit for decompression. This also affects
+ the --list mode. If the operation is not possible without
+ exceeding the limit, xz will display an error and decompressing
+ the file will fail. See --memlimit-compress=limit for possible
+ ways to specify the limit.
+
+ -M limit, --memlimit=limit, --memory=limit
+ This is equivalent to specifying --memlimit-compress=limit
+ --memlimit-decompress=limit.
+
+ --no-adjust
+ Display an error and exit if the compression settings exceed the
+ the memory usage limit. The default is to adjust the settings
+ downwards so that the memory usage limit is not exceeded. Auto-
+ matic adjusting is always disabled when creating raw streams
+ (--format=raw).
-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.
+ Specify the number of worker threads to use. The actual number
+ of threads can be less than threads if using more threads would
+ exceed the memory usage limit.
- Multithreaded compression and decompression are not implemented
+ Multithreaded compression and decompression are not implemented
yet, so this option has no effect for now.
+ As of writing (2010-09-27), it hasn't been decided if threads
+ will be used by default on multicore systems once support for
+ threading has been implemented. Comments are welcome. The com-
+ plicating factor is that using many threads will increase the
+ memory usage dramatically. Note that if multithreading will be
+ the default, it will probably be done so that single-threaded
+ and multithreaded modes produce the same output, so compression
+ ratio won't be significantly affected if threading will be
+ enabled by default.
+
Custom compressor filter chains
- A custom filter chain allows specifying the compression settings in
+ 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
+ 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.
+ A filter chain is comparable to piping on the command line. When com-
+ pressing, 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 fil-
+ ters.
- 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.
+ Many filters have limitations on 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
+ 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.
+ 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[=options]
+ --lzma2[=options]
+ Add LZMA1 or LZMA2 filter to the filter chain. These filters
+ 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
+ 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.
+ 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-
+ memory. The algorithm tries to find repeating byte
+ sequences (matches) in the uncompressed data, and replace
+ them with references to the data currently in the dictio-
+ nary. The bigger the dictionary, the higher is the
+ chance to find a match. Thus, increasing dictionary size
+ usually improves compression ratio, but a dictionary big-
+ ger than the uncompressed file is waste of memory.
+
+ 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 (1536 MiB). The decompressor already sup-
+ ports dictionaries up to one byte less than 4 GiB, which
+ is the maximum for the LZMA1 and LZMA2 stream formats.
+
+ Dictionary size and match finder (mf) together determine
+ the memory usage of the LZMA1 or LZMA2 encoder. The same
+ (or bigger) 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. The .xz headers store the dictionary
+ size either as 2^n or 2^n + 2^(n-1), so these sizes are
+ somewhat preferred for compression. Other sizes will get
+ rounded up when stored in the .xz headers.
+
+ 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
+ All bytes that cannot be encoded as matches are encoded
+ as literals. That is, literals are simply 8-bit bytes
+ that are encoded one at a time.
+
+ The literal coding makes an assumption that the highest
+ lc bits of the previous uncompressed byte correlate with
+ the next byte. E.g. in typical English text, an upper-
+ case letter is often followed by a lower-case letter, and
+ a lower-case letter is usually followed by another lower-
+ case letter. In the US-ASCII character set, the highest
+ three bits are 010 for upper-case letters and 011 for
+ lower-case letters. When lc is at least 3, the literal
+ coding can take advantage of this property in the uncom-
+ pressed data.
+
+ The default value (3) is usually good. If you want maxi-
+ mum compression, test lc=4. Sometimes it helps a little,
+ and sometimes it makes compression worse. If it makes it
+ worse, test e.g. lc=2 too.
+
+ 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.
+ Lp affects what kind of alignment in the uncompressed
+ data is assumed when encoding literals. See pb below for
+ more information about alignment.
+
+ pb=pb Specify the number of position bits. The minimum is 0
+ and the maximum is 4; the default is 2.
+
+ Pb affects what kind of alignment in the uncompressed
+ data is assumed in general. The default means four-byte
+ alignment (2^pb=2^2=4), which is often a good choice when
+ there's no better guess.
+
+ When the aligment is known, setting pb accordingly may
+ reduce the file size a little. E.g. with text files hav-
+ ing one-byte alignment (US-ASCII, ISO-8859-*, UTF-8),
+ setting pb=0 can improve compression slightly. For
+ UTF-16 text, pb=1 is a good choice. If the alignment is
+ an odd number like 3 bytes, pb=0 might be the best
+ choice.
+
+ Even though the assumed alignment can be adjusted with pb
+ and lp, LZMA1 and LZMA2 still slightly favor 16-byte
+ alignment. It might be worth taking into account when
+ designing file formats that are likely to be often com-
+ pressed with LZMA1 or LZMA2.
+
+ 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. The
+ default depends on the preset: 0 uses hc3, 1-3 use hc4,
+ and the rest use bt4.
+
+ The following match finders are supported. The memory
+ usage formulas below are rough approximations, which are
+ closest to the 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);
+ 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
+ Memory usage:
+ dict * 7.5 (if dict <= 32 MiB);
+ dict * 6.5 (if dict > 32 MiB)
bt2 Binary Tree with 2-byte hashing
Minimum value for nice: 2
@@ -530,202 +650,235 @@ OPTIONS
bt3 Binary Tree with 2- and 3-byte hashing
Minimum value for nice: 3
- Memory usage: dict * 11.5 (if dict <= 16 MiB);
+ 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
+ Memory usage:
+ dict * 11.5 (if dict <= 32 MiB);
+ dict * 10.5 (if dict > 32 MiB)
+
+ mode=mode
+ Compression mode specifies the method to analyze the data
+ produced by the match finder. Supported modes are fast
+ and normal. The default is fast for presets 0-3 and nor-
+ mal for presets 4-9.
+
+ Usually fast is used with Hash Chain match finders and
+ normal with Binary Tree match finders. This is also what
+ the presets do.
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.
+ Nice can be 2-273 bytes. Higher values tend to give bet-
+ ter compression ratio at the expense of speed. The
+ default depends on the preset.
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.
+ Specify the maximum search depth in the match finder.
+ The default is the special value of 0, which makes the
+ compressor 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.
+ Reasonable depth for Hash Chains is 4-100 and 16-1000 for
+ Binary Trees. Using very high values for depth can make
+ the encoder extremely slow with some files. Avoid set-
+ ting the depth over 1000 unless you are prepared to
+ interrupt the compression in case it is taking far too
+ long.
When decoding raw streams (--format=raw), LZMA2 needs only the
- value of dict. LZMA1 needs also lc, lp, and pb.
+ dictionary size. 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.
+ Add a branch/call/jump (BCJ) filter to the filter chain. These
+ filters can be used only as a 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 can help LZMA2 to
+ produce 0-15 % smaller .xz file. The BCJ filters are always
+ reversible, so using a BCJ filter for wrong type of data doesn't
+ cause any data loss, although it may make the compression ratio
+ slightly worse.
+
+ It is fine to apply a BCJ filter on a whole executable; there's
+ no need to apply it only on the executable section. Applying a
+ BCJ filter on an archive that contains both executable and non-
+ executable files may or may not give good results, so it gener-
+ ally isn't good to blindly apply a BCJ filter when compressing
+ binary packages for distribution.
+
+ These BCJ filters are very fast and use insignificant amount of
+ memory. If a BCJ filter improves compression ratio of a file,
+ it can improve decompression speed at the same time. This is
+ because, on the same hardware, the decompression speed of LZMA2
+ is roughly a fixed number of bytes of compressed data per sec-
+ ond.
+
+ These BCJ filters have known problems related to the compression
+ ratio:
+
+ o Some types of files containing executable code (e.g. object
+ files, static libraries, and Linux kernel modules) have the
+ addresses in the instructions filled with filler values.
+ These BCJ filters will still do the address conversion, which
+ will make the compression worse with these files.
+
+ o Applying a BCJ filter on an archive containing multiple simi-
+ lar executables can make the compression ratio worse than not
+ using a BCJ filter. This is because the BCJ filter doesn't
+ detect the boundaries of the executable files, and doesn't
+ reset the address conversion counter for each executable.
+
+ Both of the above problems will be fixed in the future in a new
+ filter. The old BCJ filters will still be useful in embedded
+ systems, because the decoder of the new filter will be bigger
+ and use more memory.
Different instruction sets have have different alignment:
Filter Alignment Notes
- x86 1 32-bit and 64-bit x86
+ x86 1 32-bit or 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
+ 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
+ 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
+ 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.
+ Add the Delta filter to the filter chain. The Delta filter can
+ be only used as a 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.
+ images or uncompressed PCM audio. However, special purpose
+ algorithms may give significantly better results than Delta +
+ LZMA2. This is true especially with audio, which compresses
+ faster and better e.g. with flac(1).
Supported options:
dist=distance
- Specify the distance of the delta calculation as bytes.
- distance must be 1-256. The default is 1.
+ Specify the distance of the delta calculation in 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
+ 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
+ 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).
+ will give even more verbose output.
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 Completion percentage is shown if the size of the input file
+ is known. That is, the percentage cannot be shown in pipes.
- o Amount of compressed data produced (compressing) or consumed
+ o Amount of compressed data produced (compressing) or consumed
(decompressing).
- o Amount of uncompressed data consumed (compressing) or pro-
+ 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-
+ 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 Compression or decompression speed. This is measured as the
+ amount of uncompressed data consumed (compression) or pro-
+ duced (decompression) per second. It is shown after a few
+ seconds have passed since xz started processing the file.
+
+ o Elapsed time in the format M:SS or H:MM:SS.
- 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.
+ o Estimated remaining time is shown only when the size of the
+ input file is known and a couple of seconds have already
+ passed since xz started processing the file. The time is
+ shown in a less precise format which never has any colons,
+ e.g. 2 min 30 s.
- When standard error is not a terminal, --verbose will make xz
+ 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.
+ sion ratio, and possibly also the speed and elapsed time on a
+ single line to standard error after compressing or decompressing
+ the file. The speed and elapsed time are included only when the
+ operation took at least a few seconds. If the operation didn't
+ finish, e.g. due to user interruption, also the completion per-
+ centage 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
+ 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. See the
- section ROBOT MODE for details.
+ 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. See the section ROBOT MODE for details.
--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.
+ Display, in human-readable format, how much physical memory
+ (RAM) xz thinks the system has and the memory usage limits for
+ compression and decompression, and exit successfully.
-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
+ 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
+ Display the version number of xz and liblzma in human readable
+ format. To get machine-parsable output, specify --robot before
--version.
ROBOT MODE
- The robot mode is activated with the --robot option. It makes the out-
- put of xz easier to parse by other programs. Currently --robot is sup-
- ported only together with --version, --info-memory, and --list. It
- will be supported for normal compression and decompression in the
+ The robot mode is activated with the --robot option. It makes the out-
+ put of xz easier to parse by other programs. Currently --robot is sup-
+ ported only together with --version, --info-memory, and --list. It
+ will be supported for normal compression and decompression in the
future.
Version
@@ -737,10 +890,10 @@ ROBOT MODE
X Major version.
- YYY Minor version. Even numbers are stable. Odd numbers are alpha
+ YYY Minor version. Even numbers are stable. Odd numbers are alpha
or beta versions.
- ZZZ Patch level for stable releases or just a counter for develop-
+ ZZZ Patch level for stable releases or just a counter for develop-
ment releases.
S Stability. 0 is alpha, 1 is beta, and 2 is stable. S should be
@@ -752,158 +905,129 @@ ROBOT MODE
Examples: 4.999.9beta is 49990091 and 5.0.0 is 50000002.
Memory limit information
- xz --robot --info-memory prints the current memory usage limit as bytes
- on a single line. To get the total amount of installed RAM, use xz
- --robot --memory=100% --info-memory.
+ xz --robot --info-memory prints a single line with three tab-separated
+ columns:
+
+ 1. Total amount of physical memory (RAM) in bytes
+
+ 2. Memory usage limit for compression in bytes. A special value of
+ zero indicates the default setting, which for single-threaded mode
+ is the same as no limit.
+
+ 3. Memory usage limit for decompression in bytes. A special value of
+ zero indicates the default setting, which for single-threaded mode
+ is the same as no limit.
+
+ In the future, the output of xz --robot --info-memory may have more
+ columns, but never more than a single line.
List mode
- xz --robot --list uses tab-separated output. The first column of every
- line has a string that indicates the type of the information found on
+ xz --robot --list uses tab-separated output. The first column of every
+ line has a string that indicates the type of the information found on
that line:
name This is always the first line when starting to list a file. The
second column on the line is the filename.
- file This line contains overall information about the .xz file. This
+ file This line contains overall information about the .xz file. This
line is always printed after the name line.
stream This line type is used only when --verbose was specified. There
are as many stream lines as there are streams in the .xz file.
- block This line type is used only when --verbose was specified. There
- are as many block lines as there are blocks in the .xz file. The
- block lines are shown after all the stream lines; different line
- types are not interleaved.
+ block This line type is used only when --verbose was specified. There
+ are as many block lines as there are blocks in the .xz file.
+ The block lines are shown after all the stream lines; different
+ line types are not interleaved.
summary
- This line type is used only when --verbose was specified twice.
- This line is printed after all block lines. Like the file line,
- the summary line contains overall information about the .xz
+ This line type is used only when --verbose was specified twice.
+ This line is printed after all block lines. Like the file line,
+ the summary line contains overall information about the .xz
file.
- totals This line is always the very last line of the list output. It
+ totals This line is always the very last line of the list output. It
shows the total counts and sizes.
The columns of the file lines:
-
2. Number of streams in the file
-
3. Total number of blocks in the stream(s)
-
4. Compressed size of the file
-
5. Uncompressed size of the file
-
- 6. Compression ratio, for example 0.123. If ratio is over
- 9.999, three dashes (---) are displayed instead of the
+ 6. Compression ratio, for example 0.123. If ratio is over
+ 9.999, three dashes (---) are displayed instead of the
ratio.
-
- 7. Comma-separated list of integrity check names. The following
- strings are used for the known check types: None, CRC32,
- CRC64, and SHA-256. For unknown check types, Unknown-N is
- used, where N is the Check ID as a decimal number (one or
+ 7. Comma-separated list of integrity check names. The follow-
+ ing strings are used for the known check types: None, CRC32,
+ CRC64, and SHA-256. For unknown check types, Unknown-N is
+ used, where N is the Check ID as a decimal number (one or
two digits).
-
8. Total size of stream padding in the file
The columns of the stream lines:
-
2. Stream number (the first stream is 1)
-
3. Number of blocks in the stream
-
4. Compressed start offset
-
5. Uncompressed start offset
-
6. Compressed size (does not include stream padding)
-
7. Uncompressed size
-
8. Compression ratio
-
9. Name of the integrity check
-
10. Size of stream padding
The columns of the block lines:
-
2. Number of the stream containing this block
-
- 3. Block number relative to the beginning of the stream (the
+ 3. Block number relative to the beginning of the stream (the
first block is 1)
-
4. Block number relative to the beginning of the file
-
- 5. Compressed start offset relative to the beginning of the
+ 5. Compressed start offset relative to the beginning of the
file
-
- 6. Uncompressed start offset relative to the beginning of the
+ 6. Uncompressed start offset relative to the beginning of the
file
-
7. Total compressed size of the block (includes headers)
-
8. Uncompressed size
-
9. Compression ratio
-
10. Name of the integrity check
- If --verbose was specified twice, additional columns are included on
- the block lines. These are not displayed with a single --verbose,
- because getting this information requires many seeks and can thus be
+ If --verbose was specified twice, additional columns are included on
+ the block lines. These are not displayed with a single --verbose,
+ because getting this information requires many seeks and can thus be
slow:
-
11. Value of the integrity check in hexadecimal
-
12. Block header size
-
- 13. Block flags: c indicates that compressed size is present,
- and u indicates that uncompressed size is present. If the
- flag is not set, a dash (-) is shown instead to keep the
- string length fixed. New flags may be added to the end of
+ 13. Block flags: c indicates that compressed size is present,
+ and u indicates that uncompressed size is present. If the
+ flag is not set, a dash (-) is shown instead to keep the
+ string length fixed. New flags may be added to the end of
the string in the future.
-
- 14. Size of the actual compressed data in the block (this
+ 14. Size of the actual compressed data in the block (this
excludes the block header, block padding, and check fields)
-
- 15. Amount of memory (as bytes) required to decompress this
+ 15. Amount of memory (in bytes) required to decompress this
block with this xz version
-
- 16. Filter chain. Note that most of the options used at compres-
- sion time cannot be known, because only the options that are
- needed for decompression are stored in the .xz headers.
+ 16. Filter chain. Note that most of the options used at com-
+ pression time cannot be known, because only the options that
+ are needed for decompression are stored in the .xz headers.
The columns of the totals line:
-
2. Number of streams
-
3. Number of blocks
-
4. Compressed size
-
5. Uncompressed size
-
6. Average compression ratio
-
- 7. Comma-separated list of integrity check names that were
+ 7. Comma-separated list of integrity check names that were
present in the files
-
8. Stream padding size
-
- 9. Number of files. This is here to keep the order of the ear-
+ 9. Number of files. This is here to keep the order of the ear-
lier columns the same as on file lines.
- If --verbose was specified twice, additional columns are included on
+ If --verbose was specified twice, additional columns are included on
the totals line:
-
- 10. Maximum amount of memory (as bytes) required to decompress
+ 10. Maximum amount of memory (in bytes) required to decompress
the files with this xz version
-
- 11. yes or no indicating if all block headers have both com-
+ 11. yes or no indicating if all block headers have both com-
pressed size and uncompressed size stored in them
- Future versions may add new line types and new columns can be added to
+ Future versions may add new line types and new columns can be added to
the existing line types, but the existing columns won't be changed.
EXIT STATUS
@@ -918,98 +1042,124 @@ EXIT STATUS
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.
+ xz parses space-separated lists of options from the environment vari-
+ ables XZ_DEFAULTS and XZ_OPT, in this order, before parsing the options
+ from the command line. Note that only options are parsed from the
+ environment variables; all non-options are silently ignored. Parsing
+ is done with getopt_long(3) which is used also for the command line
+ arguments.
+
+ XZ_DEFAULTS
+ User-specific or system-wide default options. Typically this is
+ set in a shell initialization script to enable xz's memory usage
+ limiter by default. Excluding shell initialization scripts and
+ similar special cases, scripts must never set or unset
+ XZ_DEFAULTS.
+
+ XZ_OPT This is for passing options to xz when it is not possible to set
+ the options directly on the xz command line. This is the case
+ e.g. when xz is run by a script or tool, e.g. GNU tar(1):
+
+ XZ_OPT=-2v tar caf foo.tar.xz foo
+
+ Scripts may use XZ_OPT e.g. to set script-specific default com-
+ pression options. It is still recommended to allow users to
+ override XZ_OPT if that is reasonable, e.g. in sh(1) scripts one
+ may use something like this:
+
+ XZ_OPT=${XZ_OPT-"-7e"}
+ export XZ_OPT
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.
+ 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 exist-
+ ing scripts. There are some incompatibilities though, which may some-
+ times 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 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
+ -0 256 KiB N/A
+ -1 1 MiB 64 KiB
+ -2 2 MiB 1 MiB
+ -3 4 MiB 512 KiB
+ -4 4 MiB 1 MiB
+
+ -5 8 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,
+ 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
+ -0 3 MiB N/A
+ -1 9 MiB 2 MiB
+ -2 17 MiB 12 MiB
+ -3 32 MiB 12 MiB
+ -4 48 MiB 16 MiB
+ -5 94 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.
+ The default preset level in LZMA Utils is -7 while in XZ Utils it is
+ -6, so both use an 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
+ The 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
+ example 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 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
+ 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
+ LZMA Utils creates only .lzma files which have a dictionary size of 2^n
+ (a power of 2) but accepts files with any dictionary size. liblzma
+ accepts only .lzma files which have a 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
+ 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.
+ 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
+ file to be corrupt. This may break obscure scripts which have assumed
that trailing garbage is ignored.
NOTES
@@ -1017,9 +1167,9 @@ NOTES
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.
+ ter compression) without affecting the file format. The output can
+ vary even between different builds of the same XZ Utils version, if
+ different 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
@@ -1027,9 +1177,9 @@ NOTES
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.
+ sarily support files created with integrity 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-
@@ -1040,31 +1190,169 @@ NOTES
EXAMPLES
Basics
+ Compress the file foo into foo.xz using the default compression level
+ (-6), and remove foo if compression is successful:
+
+ xz foo
+
+ Decompress bar.xz into bar and don't remove bar.xz even if decompres-
+ sion is successful:
+
+ xz -dk bar.xz
+
+ Create baz.tar.xz with the preset -4e (-4 --extreme), which is slower
+ than e.g. the default -6, but needs less memory for compression and
+ decompression (48 MiB and 5 MiB, respectively):
+
+ tar cf - baz | xz -4e > baz.tar.xz
+
A mix of compressed and uncompressed files can be decompressed to stan-
dard output with a single command:
- xz -dcf a.txt b.txt.xz c.txt d.txt.xz > abcd.txt
+ xz -dcf a.txt b.txt.xz c.txt d.txt.lzma > abcd.txt
Parallel compression of many files
- On GNU and *BSD, find(1) and xargs(1) can be used to parallellize com-
+ On GNU and *BSD, find(1) and xargs(1) can be used to parallelize com-
pression of many files:
- find . -type f \! -name '*.xz' -print0 | xargs -0r -P4 -n16 xz
+ find . -type f \! -name '*.xz' -print0 \
+ | xargs -0r -P4 -n16 xz -T1
- The -P option sets the number of parallel xz processes. The best value
- for the -n option depends on how many files there are to be compressed.
- If there are only a couple of files, the value should probably be 1;
- with tens of thousands of files, 100 or even more may be appropriate to
- reduce the number of xz processes that xargs(1) will eventually create.
+ The -P option to xargs(1) sets the number of parallel xz processes.
+ The best value for the -n option depends on how many files there are to
+ be compressed. If there are only a couple of files, the value should
+ probably be 1; with tens of thousands of files, 100 or even more may be
+ appropriate to reduce the number of xz processes that xargs(1) will
+ eventually create.
- Robot mode examples
- Calculating how many bytes have been saved in total after compressing
+ The option -T1 for xz is there to force it to single-threaded mode,
+ because xargs(1) is used to control the amount of parallelization.
+
+ Robot mode
+ Calculate how many bytes have been saved in total after compressing
multiple files:
xz --robot --list *.xz | awk '/^totals/{print $5-$4}'
+ A script may want to know that it is using new enough xz. The follow-
+ ing sh(1) script checks that the version number of the xz tool is at
+ least 5.0.0. This method is compatible with old beta versions, which
+ didn't support the --robot option:
+
+ if ! eval "$(xz --robot --version 2> /dev/null)" ||
+ [ "$XZ_VERSION" -lt 50000002 ]; then
+ echo "Your xz is too old."
+ fi
+ unset XZ_VERSION LIBLZMA_VERSION
+
+ Set a memory usage limit for decompression using XZ_OPT, but if a limit
+ has already been set, don't increase it:
+
+ NEWLIM=$((123 << 20)) # 123 MiB
+ OLDLIM=$(xz --robot --info-memory | cut -f3)
+ if [ $OLDLIM -eq 0 -o $OLDLIM -gt $NEWLIM ]; then
+ XZ_OPT="$XZ_OPT --memlimit-decompress=$NEWLIM"
+ export XZ_OPT
+ fi
+
+ Custom compressor filter chains
+ The simplest use for custom filter chains is customizing a LZMA2 pre-
+ set. This can be useful, because the presets cover only a subset of
+ the potentially useful combinations of compression settings.
+
+ The CompCPU columns of the tables from the descriptions of the options
+ -0 ... -9 and --extreme are useful when customizing LZMA2 presets.
+ Here are the relevant parts collected from those two tables:
+
+ Preset CompCPU
+ -0 0
+ -1 1
+ -2 2
+ -3 3
+ -4 4
+ -5 5
+ -6 6
+ -5e 7
+ -6e 8
+
+ If you know that a file requires somewhat big dictionary (e.g. 32 MiB)
+ to compress well, but you want to compress it quicker than xz -8 would
+ do, a preset with a low CompCPU value (e.g. 1) can be modified to use a
+ bigger dictionary:
+
+ xz --lzma2=preset=1,dict=32MiB foo.tar
+
+ With certain files, the above command may be faster than xz -6 while
+ compressing significantly better. However, it must be emphasized that
+ only some files benefit from a big dictionary while keeping the CompCPU
+ value low. The most obvious situation, where a big dictionary can help
+ a lot, is an archive containing very similar files of at least a few
+ megabytes each. The dictionary size has to be significantly bigger
+ than any individual file to allow LZMA2 to take full advantage of the
+ similarities between consecutive files.
+
+ If very high compressor and decompressor memory usage is fine, and the
+ file being compressed is at least several hundred megabytes, it may be
+ useful to use an even bigger dictionary than the 64 MiB that xz -9
+ would use:
+
+ xz -vv --lzma2=dict=192MiB big_foo.tar
+
+ Using -vv (--verbose --verbose) like in the above example can be useful
+ to see the memory requirements of the compressor and decompressor.
+ Remember that using a dictionary bigger than the size of the uncom-
+ pressed file is waste of memory, so the above command isn't useful for
+ small files.
+
+ Sometimes the compression time doesn't matter, but the decompressor
+ memory usage has to be kept low e.g. to make it possible to decompress
+ the file on an embedded system. The following command uses -6e (-6
+ --extreme) as a base and sets the dictionary to only 64 KiB. The
+ resulting file can be decompressed with XZ Embedded (that's why there
+ is --check=crc32) using about 100 KiB of memory.
+
+ xz --check=crc32 --lzma2=preset=6e,dict=64KiB foo
+
+ If you want to squeeze out as many bytes as possible, adjusting the
+ number of literal context bits (lc) and number of position bits (pb)
+ can sometimes help. Adjusting the number of literal position bits (lp)
+ might help too, but usually lc and pb are more important. E.g. a
+ source code archive contains mostly US-ASCII text, so something like
+ the following might give slightly (like 0.1 %) smaller file than xz -6e
+ (try also without lc=4):
+
+ xz --lzma2=preset=6e,pb=0,lc=4 source_code.tar
+
+ Using another filter together with LZMA2 can improve compression with
+ certain file types. E.g. to compress a x86-32 or x86-64 shared library
+ using the x86 BCJ filter:
+
+ xz --x86 --lzma2 libfoo.so
+
+ Note that the order of the filter options is significant. If --x86 is
+ specified after --lzma2, xz will give an error, because there cannot be
+ any filter after LZMA2, and also because the x86 BCJ filter cannot be
+ used as the last filter in the chain.
+
+ The Delta filter together with LZMA2 can give good results with bitmap
+ images. It should usually beat PNG, which has a few more advanced fil-
+ ters than simple delta but uses Deflate for the actual compression.
+
+ The image has to be saved in uncompressed format, e.g. as uncompressed
+ TIFF. The distance parameter of the Delta filter is set to match the
+ number of bytes per pixel in the image. E.g. 24-bit RGB bitmap needs
+ dist=3, and it is also good to pass pb=0 to LZMA2 to accommodate the
+ three-byte alignment:
+
+ xz --delta=dist=3 --lzma2=pb=0 foo.tiff
+
+ If multiple images have been put into a single archive (e.g. .tar), the
+ Delta filter will work on that too as long as all images have the same
+ number of bytes per pixel.
+
SEE ALSO
- xzdec(1), gzip(1), bzip2(1)
+ xzdec(1), xzdiff(1), xzgrep(1), xzless(1), xzmore(1), gzip(1),
+ bzip2(1), 7z(1)
XZ Utils: <http://tukaani.org/xz/>
XZ Embedded: <http://tukaani.org/xz/embedded.html>
@@ -1072,4 +1360,4 @@ SEE ALSO
-Tukaani 2010-06-01 XZ(1)
+Tukaani 2010-10-04 XZ(1)
diff --git a/Build/source/extra/xz/doc/man/txt/xzdec.txt b/Build/source/extra/xz/doc/man/txt/xzdec.txt
index bbd39f32dcb..7801afa7c93 100644
--- a/Build/source/extra/xz/doc/man/txt/xzdec.txt
+++ b/Build/source/extra/xz/doc/man/txt/xzdec.txt
@@ -18,11 +18,11 @@ DESCRIPTION
lzmadec supports .lzma files instead of .xz files.
To reduce the size of the executable, xzdec doesn't support multi-
- threading or localization, and doesn't read options from XZ_OPT envi-
- ronment variable. xzdec doesn't support displaying intermediate
- progress information: sending SIGINFO to xzdec does nothing, but send-
- ing SIGUSR1 terminates the process instead of displaying progress
- information.
+ threading or localization, and doesn't read options from XZ_DEFAULTS
+ and XZ_OPT environment variables. xzdec doesn't support displaying
+ intermediate progress information: sending SIGINFO to xzdec does noth-
+ ing, but sending SIGUSR1 terminates the process instead of displaying
+ progress information.
OPTIONS
-d, --decompress, --uncompress
@@ -37,27 +37,6 @@ OPTIONS
Ignored for xz(1) compatibility. xzdec always writes the decom-
pressed data to standard output.
- -M limit, --memory=limit
- Set the memory usage limit. If this option is specified multi-
- ple 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.
-
- 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 --help option.
-
-q, --quiet
Specifying this once does nothing since xzdec never displays any
warnings or notices. Specify this twice to suppress errors.
@@ -81,10 +60,14 @@ EXIT STATUS
status 2 is not used by xzdec.
NOTES
- xzdec and lzmadec are not really that small. The size can be reduced
+ Use xz(1) instead of xzdec or lzmadec for normal everyday use. xzdec
+ or lzmadec are meant only for situations where it is important to have
+ a smaller decompressor than the full-featured xz(1).
+
+ xzdec and lzmadec are not really that small. The size can be reduced
further by dropping features from liblzma at compile time, but that
shouldn't usually be done for executables distributed in typical non-
- embedded operating system distributions. If you need a truly small .xz
+ embedded operating system distributions. If you need a truly small .xz
decompressor, consider using XZ Embedded.
SEE ALSO
@@ -94,4 +77,4 @@ SEE ALSO
-Tukaani 2010-03-07 XZDEC(1)
+Tukaani 2010-09-27 XZDEC(1)
diff --git a/Build/source/extra/xz/doc/man/txt/xzdiff.txt b/Build/source/extra/xz/doc/man/txt/xzdiff.txt
index 0e7b2d1ee32..99af443b2cc 100644
--- a/Build/source/extra/xz/doc/man/txt/xzdiff.txt
+++ b/Build/source/extra/xz/doc/man/txt/xzdiff.txt
@@ -14,12 +14,12 @@ SYNOPSIS
DESCRIPTION
xzcmp and xzdiff invoke cmp(1) or diff(1) on files compressed with
xz(1), lzma(1), gzip(1), or bzip2(1). All options specified are passed
- directly to cmp or diff. If only one file is specified, then the files
- compared are file1 (which must have a suffix of a supported compression
- format) and file1 from which the compression format suffix has been
- stripped. If two files are specified, then they are uncompressed if
- necessary and fed to cmp(1) or diff(1). The exit status from cmp or
- diff is preserved.
+ directly to cmp(1) or diff(1). If only one file is specified, then the
+ files compared are file1 (which must have a suffix of a supported com-
+ pression format) and file1 from which the compression format suffix has
+ been stripped. If two files are specified, then they are uncompressed
+ if necessary and fed to cmp(1) or diff(1). The exit status from cmp(1)
+ or diff(1) is preserved.
The names lzcmp and lzdiff are provided for backward compatibility with
LZMA Utils.
@@ -33,4 +33,4 @@ BUGS
-Tukaani 2009-07-05 XZDIFF(1)
+Tukaani 2010-09-27 XZDIFF(1)
diff --git a/Build/source/extra/xz/doc/man/txt/xzgrep.txt b/Build/source/extra/xz/doc/man/txt/xzgrep.txt
index 7f665bce295..cdffd0735cf 100644
--- a/Build/source/extra/xz/doc/man/txt/xzgrep.txt
+++ b/Build/source/extra/xz/doc/man/txt/xzgrep.txt
@@ -18,9 +18,9 @@ DESCRIPTION
compressed with xz(1), lzma(1), gzip(1), or bzip2(1). All options
specified are passed directly to grep(1).
- If no file is specified, then the standard input is decompressed if
- necessary and fed to grep(1). When reading from standard input,
- gzip(1) and bzip2(1) compressed files are not supported.
+ If no file is specified, then standard input is decompressed if neces-
+ sary and fed to grep(1). When reading from standard input, gzip(1) and
+ bzip2(1) compressed files are not supported.
If xzgrep is invoked as xzegrep or xzfgrep then egrep(1) or fgrep(1) is
used instead of grep(1). The same applies to names lzgrep, lzegrep,
@@ -36,4 +36,4 @@ SEE ALSO
-Tukaani 2009-07-05 XZGREP(1)
+Tukaani 2010-09-27 XZGREP(1)
diff --git a/Build/source/extra/xz/doc/man/txt/xzless.txt b/Build/source/extra/xz/doc/man/txt/xzless.txt
index cacb752ee0b..5c14c80c235 100644
--- a/Build/source/extra/xz/doc/man/txt/xzless.txt
+++ b/Build/source/extra/xz/doc/man/txt/xzless.txt
@@ -36,4 +36,4 @@ SEE ALSO
-Tukaani 2009-07-05 XZLESS(1)
+Tukaani 2010-09-27 XZLESS(1)
diff --git a/Build/source/extra/xz/doc/man/txt/xzmore.txt b/Build/source/extra/xz/doc/man/txt/xzmore.txt
index 6f6cfe93eea..a32f44077e9 100644
--- a/Build/source/extra/xz/doc/man/txt/xzmore.txt
+++ b/Build/source/extra/xz/doc/man/txt/xzmore.txt
@@ -31,4 +31,4 @@ SEE ALSO
-Tukaani 2009-07-05 XZMORE(1)
+Tukaani 2010-09-27 XZMORE(1)