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Signed-off-by: Daniel Baumann <daniel@debian.org>
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@ -11,13 +11,13 @@ File: plzip.info, Node: Top, Next: Introduction, Up: (dir)
Plzip Manual
************
This manual is for Plzip (version 1.10, 24 January 2022).
This manual is for Plzip (version 1.11, 21 January 2024).
* Menu:
* Introduction:: Purpose and features of plzip
* Output:: Meaning of plzip's output
* Invoking plzip:: Command line interface
* Invoking plzip:: Command-line interface
* Program design:: Internal structure of plzip
* Memory requirements:: Memory required to compress and decompress
* Minimum file sizes:: Minimum file sizes required for full speed
@ -28,7 +28,7 @@ This manual is for Plzip (version 1.10, 24 January 2022).
* Concept index:: Index of concepts
Copyright (C) 2009-2022 Antonio Diaz Diaz.
Copyright (C) 2009-2024 Antonio Diaz Diaz.
This manual is free documentation: you have unlimited permission to copy,
distribute, and modify it.
@ -39,19 +39,20 @@ File: plzip.info, Node: Introduction, Next: Output, Prev: Top, Up: Top
1 Introduction
**************
Plzip is a massively parallel (multi-threaded) implementation of lzip, fully
Plzip is a massively parallel (multi-threaded) implementation of lzip,
compatible with lzip 1.4 or newer. Plzip uses the compression library lzlib.
Lzip is a lossless data compressor with a user interface similar to the
one of gzip or bzip2. Lzip uses a simplified form of the 'Lempel-Ziv-Markov
chain-Algorithm' (LZMA) stream format and provides a 3 factor integrity
checking to maximize interoperability and optimize safety. Lzip can compress
about as fast as gzip (lzip -0) or compress most files more than bzip2
(lzip -9). Decompression speed is intermediate between gzip and bzip2. Lzip
is better than gzip and bzip2 from a data recovery perspective. Lzip has
been designed, written, and tested with great care to replace gzip and
bzip2 as the standard general-purpose compressed format for unix-like
systems.
chain-Algorithm' (LZMA) stream format to maximize interoperability. The
maximum dictionary size is 512 MiB so that any lzip file can be decompressed
on 32-bit machines. Lzip provides accurate and robust 3-factor integrity
checking. Lzip can compress about as fast as gzip (lzip -0) or compress most
files more than bzip2 (lzip -9). Decompression speed is intermediate between
gzip and bzip2. Lzip is better than gzip and bzip2 from a data recovery
perspective. Lzip has been designed, written, and tested with great care to
replace gzip and bzip2 as the standard general-purpose compressed format for
Unix-like systems.
Plzip can compress/decompress large files on multiprocessor machines much
faster than lzip, at the cost of a slightly reduced compression ratio (0.4
@ -94,10 +95,10 @@ byte near the beginning is a thing of the past.
makes it safer than compressors returning ambiguous warning values (like
gzip) when it is used as a back end for other programs like tar or zutils.
Plzip will automatically use for each file the largest dictionary size
that does not exceed neither the file size nor the limit given. Keep in
mind that the decompression memory requirement is affected at compression
time by the choice of dictionary size limit. *Note Memory requirements::.
Plzip automatically uses for each file the largest dictionary size that
does not exceed neither the file size nor the limit given. Keep in mind
that the decompression memory requirement is affected at compression time
by the choice of dictionary size limit. *Note Memory requirements::.
When compressing, plzip replaces every file given in the command line
with a compressed version of itself, with the name "original_name.lz". When
@ -109,22 +110,22 @@ filename.tlz becomes filename.tar
anyothername becomes anyothername.out
(De)compressing a file is much like copying or moving it. Therefore plzip
preserves the access and modification dates, permissions, and, when
possible, ownership of the file just as 'cp -p' does. (If the user ID or
the group ID can't be duplicated, the file permission bits S_ISUID and
S_ISGID are cleared).
preserves the access and modification dates, permissions, and, if you have
appropriate privileges, ownership of the file just as 'cp -p' does. (If the
user ID or the group ID can't be duplicated, the file permission bits
S_ISUID and S_ISGID are cleared).
Plzip is able to read from some types of non-regular files if either the
option '-c' or the option '-o' is specified.
Plzip will refuse to read compressed data from a terminal or write
compressed data to a terminal, as this would be entirely incomprehensible
and might leave the terminal in an abnormal state.
Plzip refuses to read compressed data from a terminal or write compressed
data to a terminal, as this would be entirely incomprehensible and might
leave the terminal in an abnormal state.
Plzip will correctly decompress a file which is the concatenation of two
or more compressed files. The result is the concatenation of the
corresponding decompressed files. Integrity testing of concatenated
compressed files is also supported.
Plzip correctly decompresses a file which is the concatenation of two or
more compressed files. The result is the concatenation of the corresponding
decompressed files. Integrity testing of concatenated compressed files is
also supported.

File: plzip.info, Node: Output, Next: Invoking plzip, Prev: Introduction, Up: Top
@ -185,7 +186,8 @@ The format for running plzip is:
If no file names are specified, plzip compresses (or decompresses) from
standard input to standard output. A hyphen '-' used as a FILE argument
means standard input. It can be mixed with other FILES and is read just
once, the first time it appears in the command line.
once, the first time it appears in the command line. Remember to prepend
'./' to any file name beginning with a hyphen, or use '--'.
plzip supports the following options: *Note Argument syntax:
(arg_parser)Argument syntax.
@ -208,30 +210,32 @@ once, the first time it appears in the command line.
'-B BYTES'
'--data-size=BYTES'
When compressing, set the size in bytes of the input data blocks. The
input file will be divided in chunks of this size before compression is
input file is divided in chunks of this size before compression is
performed. Valid values range from 8 KiB to 1 GiB. Default value is
two times the dictionary size, except for option '-0' where it
defaults to 1 MiB. Plzip will reduce the dictionary size if it is
larger than the data size specified. *Note Minimum file sizes::.
defaults to 1 MiB. Plzip reduces the dictionary size if it is larger
than the data size specified. *Note Minimum file sizes::.
'-c'
'--stdout'
Compress or decompress to standard output; keep input files unchanged.
If compressing several files, each file is compressed independently.
This option (or '-o') is needed when reading from a named pipe (fifo)
or from a device. Use 'lziprecover -cd -i' to recover as much of the
decompressed data as possible when decompressing a corrupt file. '-c'
overrides '-o'. '-c' has no effect when testing or listing.
(The output consists of a sequence of independently compressed
members). This option (or '-o') is needed when reading from a named
pipe (fifo) or from a device. Use 'lziprecover -cd -i' to recover as
much of the decompressed data as possible when decompressing a corrupt
file. '-c' overrides '-o'. '-c' has no effect when testing or listing.
'-d'
'--decompress'
Decompress the files specified. If a file does not exist, can't be
opened, or the destination file already exists and '--force' has not
been specified, plzip continues decompressing the rest of the files
and exits with error status 1. If a file fails to decompress, or is a
terminal, plzip exits immediately with error status 2 without
decompressing the rest of the files. A terminal is considered an
uncompressed file, and therefore invalid.
Decompress the files specified. The integrity of the files specified is
checked. If a file does not exist, can't be opened, or the destination
file already exists and '--force' has not been specified, plzip
continues decompressing the rest of the files and exits with error
status 1. If a file fails to decompress, or is a terminal, plzip exits
immediately with error status 2 without decompressing the rest of the
files. A terminal is considered an uncompressed file, and therefore
invalid.
'-f'
'--force'
@ -258,18 +262,18 @@ once, the first time it appears in the command line.
printed.
If any file is damaged, does not exist, can't be opened, or is not
regular, the final exit status will be > 0. '-lq' can be used to verify
regular, the final exit status is > 0. '-lq' can be used to check
quickly (without decompressing) the structural integrity of the files
specified. (Use '--test' to verify the data integrity). '-alq'
additionally verifies that none of the files specified contain
trailing data.
specified. (Use '--test' to check the data integrity). '-alq'
additionally checks that none of the files specified contain trailing
data.
'-m BYTES'
'--match-length=BYTES'
When compressing, set the match length limit in bytes. After a match
this long is found, the search is finished. Valid values range from 5
to 273. Larger values usually give better compression ratios but longer
compression times.
to 273. Larger values usually give better compression ratios but
longer compression times.
'-n N'
'--threads=N'
@ -291,10 +295,12 @@ once, the first time it appears in the command line.
'-o FILE'
'--output=FILE'
If '-c' has not been also specified, write the (de)compressed output to
FILE; keep input files unchanged. If compressing several files, each
file is compressed independently. This option (or '-c') is needed when
reading from a named pipe (fifo) or from a device. '-o -' is
If '-c' has not been also specified, write the (de)compressed output
to FILE, automatically creating any missing parent directories; keep
input files unchanged. If compressing several files, each file is
compressed independently. (The output consists of a sequence of
independently compressed members). This option (or '-c') is needed
when reading from a named pipe (fifo) or from a device. '-o -' is
equivalent to '-c'. '-o' has no effect when testing or listing.
In order to keep backward compatibility with plzip versions prior to
@ -311,14 +317,14 @@ once, the first time it appears in the command line.
'-s BYTES'
'--dictionary-size=BYTES'
When compressing, set the dictionary size limit in bytes. Plzip will
use for each file the largest dictionary size that does not exceed
neither the file size nor this limit. Valid values range from 4 KiB to
512 MiB. Values 12 to 29 are interpreted as powers of two, meaning
2^12 to 2^29 bytes. Dictionary sizes are quantized so that they can be
coded in just one byte (*note coded-dict-size::). If the size specified
does not match one of the valid sizes, it will be rounded upwards by
adding up to (BYTES / 8) to it.
When compressing, set the dictionary size limit in bytes. Plzip uses
for each file the largest dictionary size that does not exceed neither
the file size nor this limit. Valid values range from 4 KiB to 512 MiB.
Values 12 to 29 are interpreted as powers of two, meaning 2^12 to 2^29
bytes. Dictionary sizes are quantized so that they can be coded in
just one byte (*note coded-dict-size::). If the size specified does
not match one of the valid sizes, it is rounded upwards by adding up
to (BYTES / 8) to it.
For maximum compression you should use a dictionary size limit as large
as possible, but keep in mind that the decompression memory requirement
@ -330,7 +336,7 @@ once, the first time it appears in the command line.
really performs a trial decompression and throws away the result. Use
it together with '-v' to see information about the files. If a file
fails the test, does not exist, can't be opened, or is a terminal,
plzip continues checking the rest of the files. A final diagnostic is
plzip continues testing the rest of the files. A final diagnostic is
shown at verbosity level 1 or higher if any file fails the test when
testing multiple files.
@ -408,26 +414,29 @@ once, the first time it appears in the command line.
(lzlib)Library version.
Numbers given as arguments to options may be followed by a multiplier
and an optional 'B' for "byte".
Numbers given as arguments to options may be expressed in decimal,
hexadecimal, or octal (using the same syntax as integer constants in C++),
and may be followed by a multiplier and an optional 'B' for "byte".
Table of SI and binary prefixes (unit multipliers):
Prefix Value | Prefix Value
k kilobyte (10^3 = 1000) | Ki kibibyte (2^10 = 1024)
M megabyte (10^6) | Mi mebibyte (2^20)
G gigabyte (10^9) | Gi gibibyte (2^30)
T terabyte (10^12) | Ti tebibyte (2^40)
P petabyte (10^15) | Pi pebibyte (2^50)
E exabyte (10^18) | Ei exbibyte (2^60)
Z zettabyte (10^21) | Zi zebibyte (2^70)
Y yottabyte (10^24) | Yi yobibyte (2^80)
Prefix Value | Prefix Value
k kilobyte (10^3 = 1000) | Ki kibibyte (2^10 = 1024)
M megabyte (10^6) | Mi mebibyte (2^20)
G gigabyte (10^9) | Gi gibibyte (2^30)
T terabyte (10^12) | Ti tebibyte (2^40)
P petabyte (10^15) | Pi pebibyte (2^50)
E exabyte (10^18) | Ei exbibyte (2^60)
Z zettabyte (10^21) | Zi zebibyte (2^70)
Y yottabyte (10^24) | Yi yobibyte (2^80)
R ronnabyte (10^27) | Ri robibyte (2^90)
Q quettabyte (10^30) | Qi quebibyte (2^100)
Exit status: 0 for a normal exit, 1 for environmental problems (file not
found, invalid flags, I/O errors, etc), 2 to indicate a corrupt or invalid
input file, 3 for an internal consistency error (e.g., bug) which caused
plzip to panic.
found, invalid command-line options, I/O errors, etc), 2 to indicate a
corrupt or invalid input file, 3 for an internal consistency error (e.g.,
bug) which caused plzip to panic.

File: plzip.info, Node: Program design, Next: Memory requirements, Prev: Invoking plzip, Up: Top
@ -441,7 +450,7 @@ multimember compressed file. Each chunk is compressed in-place (using the
same buffer for input and output), reducing the amount of RAM required.
When decompressing, plzip decompresses as many members simultaneously as
worker threads are chosen. Files that were compressed with lzip will not be
worker threads are chosen. Files that were compressed with lzip are not
decompressed faster than using lzip (unless the option '-b' was used)
because lzip usually produces single-member files, which can't be
decompressed in parallel.
@ -535,10 +544,10 @@ multimember compressed file.
For this to work as expected (and roughly multiply the compression speed
by the number of available processors), the uncompressed file must be at
least as large as the number of worker threads times the chunk size (*note
--data-size::). Else some processors will not get any data to compress, and
compression will be proportionally slower. The maximum speed increase
achievable on a given file is limited by the ratio (file_size / data_size).
For example, a tarball the size of gcc or linux will scale up to 10 or 14
--data-size::). Else some processors do not get any data to compress, and
compression is proportionally slower. The maximum speed increase achievable
on a given file is limited by the ratio (file_size / data_size). For
example, a tarball the size of gcc or linux scales up to 10 or 14
processors at level -9.
The following table shows the minimum uncompressed file size needed for
@ -585,7 +594,7 @@ when there is no longer anything to take away.
represents a variable number of bytes.
A lzip file consists of a series of independent "members" (compressed
A lzip file consists of one or more independent "members" (compressed
data sets). The members simply appear one after another in the file, with no
additional information before, between, or after them. Each member can
encode in compressed form up to 16 EiB - 1 byte of uncompressed data. The
@ -629,10 +638,10 @@ size of a multimember file is unlimited.
'Member size (8 bytes)'
Total size of the member, including header and trailer. This field acts
as a distributed index, allows the verification of stream integrity,
and facilitates the safe recovery of undamaged members from
multimember files. Member size should be limited to 2 PiB to prevent
the data size field from overflowing.
as a distributed index, improves the checking of stream integrity, and
facilitates the safe recovery of undamaged members from multimember
files. Lzip limits the member size to 2 PiB to prevent the data size
field from overflowing.

@ -648,12 +657,13 @@ member. Such trailing data may be:
example when writing to a tape. It is safe to append any amount of
padding zero bytes to a lzip file.
* Useful data added by the user; a cryptographically secure hash, a
* Useful data added by the user; an "End Of File" string (to check that
the file has not been truncated), a cryptographically secure hash, a
description of file contents, etc. It is safe to append any amount of
text to a lzip file as long as none of the first four bytes of the text
match the corresponding byte in the string "LZIP", and the text does
not contain any zero bytes (null characters). Nonzero bytes and zero
bytes can't be safely mixed in trailing data.
text to a lzip file as long as none of the first four bytes of the
text matches the corresponding byte in the string "LZIP", and the text
does not contain any zero bytes (null characters). Nonzero bytes and
zero bytes can't be safely mixed in trailing data.
* Garbage added by some not totally successful copy operation.
@ -669,7 +679,7 @@ member. Such trailing data may be:
discriminate trailing data from a corrupt header has a Hamming
distance (HD) of 3, and the 3 bit flips must happen in different magic
bytes for the test to fail. In any case, the option '--trailing-error'
guarantees that any corrupt header will be detected.
guarantees that any corrupt header is detected.
Trailing data are in no way part of the lzip file format, but tools
reading lzip files are expected to behave as correctly and usefully as
@ -689,12 +699,12 @@ File: plzip.info, Node: Examples, Next: Problems, Prev: Trailing data, Up: T
WARNING! Even if plzip is bug-free, other causes may result in a corrupt
compressed file (bugs in the system libraries, memory errors, etc).
Therefore, if the data you are going to compress are important, give the
option '--keep' to plzip and don't remove the original file until you
verify the compressed file with a command like
'plzip -cd file.lz | cmp file -'. Most RAM errors happening during
compression can only be detected by comparing the compressed file with the
original because the corruption happens before plzip compresses the RAM
contents, resulting in a valid compressed file containing wrong data.
option '--keep' to plzip and don't remove the original file until you check
the compressed file with a command like 'plzip -cd file.lz | cmp file -'.
Most RAM errors happening during compression can only be detected by
comparing the compressed file with the original because the corruption
happens before plzip compresses the RAM contents, resulting in a valid
compressed file containing wrong data.
Example 1: Extract all the files from archive 'foo.tar.lz'.
@ -722,7 +732,7 @@ the operation is successful, 'file.lz' is removed.
plzip -d file.lz
Example 5: Verify the integrity of the compressed file 'file.lz' and show
Example 5: Check the integrity of the compressed file 'file.lz' and show
status.
plzip -tv file.lz
@ -800,20 +810,20 @@ Concept index
Tag Table:
Node: Top217
Node: Introduction1156
Node: Output5829
Node: Invoking plzip7392
Ref: --trailing-error8187
Ref: --data-size8425
Node: Program design18819
Node: Memory requirements21122
Node: Minimum file sizes22807
Node: File format24821
Ref: coded-dict-size26260
Node: Trailing data27514
Node: Examples29775
Ref: concat-example31210
Node: Problems31967
Node: Concept index32522
Node: Output5934
Node: Invoking plzip7497
Ref: --trailing-error8372
Ref: --data-size8610
Node: Program design19519
Node: Memory requirements21818
Node: Minimum file sizes23503
Node: File format25506
Ref: coded-dict-size26945
Node: Trailing data28195
Node: Examples30531
Ref: concat-example31964
Node: Problems32721
Node: Concept index33276

End Tag Table