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diff --git a/doc/plzip.texi b/doc/plzip.texi index b5469b9..26c0820 100644 --- a/doc/plzip.texi +++ b/doc/plzip.texi @@ -6,8 +6,8 @@ @finalout @c %**end of header -@set UPDATED 5 January 2019 -@set VERSION 1.8 +@set UPDATED 3 January 2021 +@set VERSION 1.9 @dircategory Data Compression @direntry @@ -29,6 +29,7 @@ @contents @end ifnothtml +@ifnottex @node Top @top @@ -49,35 +50,47 @@ This manual is for Plzip (version @value{VERSION}, @value{UPDATED}). @end menu @sp 1 -Copyright @copyright{} 2009-2019 Antonio Diaz Diaz. +Copyright @copyright{} 2009-2021 Antonio Diaz Diaz. -This manual is free documentation: you have unlimited permission -to copy, distribute and modify it. +This manual is free documentation: you have unlimited permission to copy, +distribute, and modify it. +@end ifnottex @node Introduction @chapter Introduction @cindex introduction -@uref{http://www.nongnu.org/lzip/plzip.html,,Plzip} is a massively parallel -(multi-threaded) implementation of lzip, fully compatible with lzip 1.4 or -newer. Plzip uses the lzlib compression library. - -@uref{http://www.nongnu.org/lzip/lzip.html,,Lzip} is a lossless data -compressor with a user interface similar to the one of gzip or bzip2. Lzip -can compress about as fast as gzip @w{(lzip -0)} or compress most files more -than bzip2 @w{(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 to 2 percent larger compressed files). Note that the number -of usable threads is limited by file size; on files larger than a few GB -plzip can use hundreds of processors, but on files of only a few MB -plzip is no faster than lzip. @xref{Minimum file sizes}. +@uref{http://www.nongnu.org/lzip/plzip.html,,Plzip} +is a massively parallel (multi-threaded) implementation of lzip, fully +compatible with lzip 1.4 or newer. Plzip uses the compression library +@uref{http://www.nongnu.org/lzip/lzlib.html,,lzlib}. + +@uref{http://www.nongnu.org/lzip/lzip.html,,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, chosen to maximize safety and +interoperability. Lzip can compress about as fast as gzip @w{(lzip -0)} or +compress most files more than bzip2 @w{(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 +to 2 percent larger compressed files). Note that the number of usable +threads is limited by file size; on files larger than a few GB plzip can use +hundreds of processors, but on files of only a few MB plzip is no faster +than lzip. @xref{Minimum file sizes}. + +For creation and manipulation of compressed tar archives +@uref{http://www.nongnu.org/lzip/manual/tarlz_manual.html,,tarlz} can be +more efficient than using tar and plzip because tarlz is able to keep the +alignment between tar members and lzip members. +@ifnothtml +@xref{Top,tarlz manual,,tarlz}. +@end ifnothtml The lzip file format is designed for data sharing and long-term archiving, taking into account both data integrity and decoder availability: @@ -85,11 +98,11 @@ taking into account both data integrity and decoder availability: @itemize @bullet @item The lzip format provides very safe integrity checking and some data -recovery means. The +recovery means. The program @uref{http://www.nongnu.org/lzip/manual/lziprecover_manual.html#Data-safety,,lziprecover} -program can repair bit flip errors (one of the most common forms of data -corruption) in lzip files, and provides data recovery capabilities, -including error-checked merging of damaged copies of a file. +can repair bit flip errors (one of the most common forms of data corruption) +in lzip files, and provides data recovery capabilities, including +error-checked merging of damaged copies of a file. @ifnothtml @xref{Data safety,,,lziprecover}. @end ifnothtml @@ -107,10 +120,10 @@ Additionally the lzip reference implementation is copylefted, which guarantees that it will remain free forever. @end itemize -A nice feature of the lzip format is that a corrupt byte is easier to -repair the nearer it is from the beginning of the file. Therefore, with -the help of lziprecover, losing an entire archive just because of a -corrupt byte near the beginning is a thing of the past. +A nice feature of the lzip format is that a corrupt byte is easier to repair +the nearer it is from the beginning of the file. Therefore, with the help of +lziprecover, losing an entire archive just because of a corrupt byte near +the beginning is a thing of the past. Plzip uses the same well-defined exit status values used by lzip, which makes it safer than compressors returning ambiguous warning values (like @@ -138,13 +151,12 @@ possible, ownership of the file just as @samp{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 the -@samp{--stdout} option is specified. +Plzip is able to read from some types of non-regular files if either the +option @samp{-c} or the option @samp{-o} is specified. -If no file names are specified, plzip compresses (or decompresses) from -standard input to standard output. In this case, plzip will decline to -write compressed output to a terminal, as this would be entirely -incomprehensible and therefore pointless. +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 will correctly decompress a file which is the concatenation of two or more compressed files. The result is the concatenation of the corresponding @@ -162,16 +174,16 @@ The output of plzip looks like this: plzip -v foo foo: 6.676:1, 14.98% ratio, 85.02% saved, 450560 in, 67493 out. -plzip -tvv foo.lz - foo.lz: 6.676:1, 14.98% ratio, 85.02% saved. ok +plzip -tvvv foo.lz + foo.lz: 6.676:1, 14.98% ratio, 85.02% saved. 450560 out, 67493 in. ok @end example The meaning of each field is as follows: @table @code @item N:1 -The compression ratio @w{(uncompressed_size / compressed_size)}, shown -as N to 1. +The compression ratio @w{(uncompressed_size / compressed_size)}, shown as +@w{N to 1}. @item ratio The inverse compression ratio @w{(compressed_size / uncompressed_size)}, @@ -182,23 +194,23 @@ decimal point two places to the left; @w{14.98% = 0.1498}. The space saved by compression @w{(1 - ratio)}, shown as a percentage. @item in -The size of the uncompressed data. When decompressing or testing, it is -shown as @code{decompressed}. Note that plzip always prints the -uncompressed size before the compressed size when compressing, -decompressing, testing or listing. +Size of the input data. This is the uncompressed size when compressing, or +the compressed size when decompressing or testing. Note that plzip always +prints the uncompressed size before the compressed size when compressing, +decompressing, testing, or listing. @item out -The size of the compressed data. When decompressing or testing, it is -shown as @code{compressed}. +Size of the output data. This is the compressed size when compressing, or +the decompressed size when decompressing or testing. @end table -When decompressing or testing at verbosity level 4 (-vvvv), the -dictionary size used to compress the file is also shown. +When decompressing or testing at verbosity level 4 (-vvvv), the dictionary +size used to compress the file is also shown. -LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never -have been compressed. Decompressed is used to refer to data which have -undergone the process of decompression. +LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never have +been compressed. Decompressed is used to refer to data which have undergone +the process of decompression. @node Invoking plzip @@ -215,11 +227,16 @@ plzip [@var{options}] [@var{files}] @end example @noindent -@samp{-} used as a @var{file} argument means standard input. It can be -mixed with other @var{files} and is read just once, the first time it -appears in the command line. +If no file names are specified, plzip compresses (or decompresses) from +standard input to standard output. A hyphen @samp{-} used as a @var{file} +argument means standard input. It can be mixed with other @var{files} and is +read just once, the first time it appears in the command line. -plzip supports the following options: +plzip supports the following +@uref{http://www.nongnu.org/arg-parser/manual/arg_parser_manual.html#Argument-syntax,,options}: +@ifnothtml +@xref{Argument syntax,,,arg_parser}. +@end ifnothtml @table @code @item -h @@ -246,18 +263,20 @@ input file will be divided in chunks of this size before compression is performed. Valid values range from @w{8 KiB} to @w{1 GiB}. Default value is two times the dictionary size, except for option @samp{-0} where it defaults to @w{1 MiB}. Plzip will reduce the dictionary size if it is -larger than the chosen data size. +larger than the data size specified. @xref{Minimum file sizes}. @item -c @itemx --stdout -Compress or decompress to standard output; keep input files unchanged. -If compressing several files, each file is compressed independently. -This option is needed when reading from a named pipe (fifo) or from a -device. +Compress or decompress to standard output; keep input files unchanged. If +compressing several files, each file is compressed independently. This +option (or @samp{-o}) is needed when reading from a named pipe (fifo) or +from a device. Use @w{@samp{lziprecover -cd -i}} to recover as much of the +decompressed data as possible when decompressing a corrupt file. @samp{-c} +overrides @samp{-o}. @samp{-c} has no effect when testing or listing. @item -d @itemx --decompress -Decompress the specified files. If a file does not exist or can't be +Decompress the files specified. If a file does not exist or can't be opened, plzip continues decompressing the rest of the files. If a file fails to decompress, or is a terminal, plzip exits immediately without decompressing the rest of the files. @@ -277,17 +296,18 @@ Keep (don't delete) input files during compression or decompression. @item -l @itemx --list -Print the uncompressed size, compressed size and percentage saved of the -specified files. Trailing data are ignored. The values produced are -correct even for multimember files. If more than one file is given, a -final line containing the cumulative sizes is printed. With @samp{-v}, -the dictionary size, the number of members in the file, and the amount -of trailing data (if any) are also printed. With @samp{-vv}, the -positions and sizes of each member in multimember files are also -printed. @samp{-lq} can be used to verify quickly (without -decompressing) the structural integrity of the specified files. (Use -@samp{--test} to verify the data integrity). @samp{-alq} additionally -verifies that none of the specified files contain trailing data. +Print the uncompressed size, compressed size, and percentage saved of the +files specified. Trailing data are ignored. The values produced are correct +even for multimember files. If more than one file is given, a final line +containing the cumulative sizes is printed. With @samp{-v}, the dictionary +size, the number of members in the file, and the amount of trailing data (if +any) are also printed. With @samp{-vv}, the positions and sizes of each +member in multimember files are also printed. + +@samp{-lq} can be used to verify quickly (without decompressing) the +structural integrity of the files specified. (Use @samp{--test} to verify +the data integrity). @samp{-alq} additionally verifies that none of the +files specified contain trailing data. @item -m @var{bytes} @itemx --match-length=@var{bytes} @@ -298,27 +318,36 @@ compression times. @item -n @var{n} @itemx --threads=@var{n} -Set the number of worker threads, overriding the system's default. Valid -values range from 1 to "as many as your system can support". If this -option is not used, plzip tries to detect the number of processors in -the system and use it as default value. When compressing on a @w{32 bit} -system, plzip tries to limit the memory use to under @w{2.22 GiB} (4 -worker threads at level -9) by reducing the number of threads below the -system's default. @w{@samp{plzip --help}} shows the system's default -value. - -Note that the number of usable threads is limited to @w{ceil( file_size -/ data_size )} during compression (@pxref{Minimum file sizes}), and to -the number of members in the input during decompression. +Set the maximum number of worker threads, overriding the system's default. +Valid values range from 1 to "as many as your system can support". If this +option is not used, plzip tries to detect the number of processors in the +system and use it as default value. When compressing on a @w{32 bit} system, +plzip tries to limit the memory use to under @w{2.22 GiB} (4 worker threads +at level -9) by reducing the number of threads below the system's default. +@w{@samp{plzip --help}} shows the system's default value. + +Plzip starts the number of threads required by each file without exceeding +the value specified. Note that the number of usable threads is limited to +@w{ceil( file_size / data_size )} during compression (@pxref{Minimum file +sizes}), and to the number of members in the input during decompression. You +can find the number of members in a lzip file by running +@w{@samp{plzip -lv file.lz}}. @item -o @var{file} @itemx --output=@var{file} -When reading from standard input and @samp{--stdout} has not been -specified, use @samp{@var{file}} as the virtual name of the uncompressed -file. This produces a file named @samp{@var{file}} when decompressing, -or a file named @samp{@var{file}.lz} when compressing. A second -@samp{.lz} extension is not added if @samp{@var{file}} already ends in -@samp{.lz} or @samp{.tlz}. +If @samp{-c} has not been also specified, write the (de)compressed output to +@var{file}; keep input files unchanged. If compressing several files, each +file is compressed independently. This option (or @samp{-c}) is needed when +reading from a named pipe (fifo) or from a device. @w{@samp{-o -}} is +equivalent to @samp{-c}. @samp{-o} has no effect when testing or listing. + +In order to keep backward compatibility with plzip versions prior to 1.9, +when compressing from standard input and no other file names are given, the +extension @samp{.lz} is appended to @var{file} unless it already ends in +@samp{.lz} or @samp{.tlz}. This feature will be removed in a future version +of plzip. Meanwhile, redirection may be used instead of @samp{-o} to write +the compressed output to a file without the extension @samp{.lz} in its +name: @w{@samp{plzip < file > foo}}. @item -q @itemx --quiet @@ -331,7 +360,7 @@ for each file the largest dictionary size that does not exceed neither the file size nor this limit. Valid values range from @w{4 KiB} to @w{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 (@pxref{coded-dict-size}). If the specified size +coded in just one byte (@pxref{coded-dict-size}). If the size specified does not match one of the valid sizes, it will be rounded upwards by adding up to @w{(@var{bytes} / 8)} to it. @@ -341,12 +370,13 @@ is affected at compression time by the choice of dictionary size limit. @item -t @itemx --test -Check integrity of the specified files, but don't decompress them. This +Check integrity of the files specified, but don't decompress them. This really performs a trial decompression and throws away the result. Use it together with @samp{-v} to see information about the files. If a file -does not exist, can't be opened, or is a terminal, plzip continues -checking the rest of the files. If a file fails the test, plzip may be -unable to check the rest of the files. +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 shown at +verbosity level 1 or higher if any file fails the test when testing +multiple files. @item -v @itemx --verbose @@ -364,12 +394,12 @@ Compression level. Set the compression parameters (dictionary size and match length limit) as shown in the table below. The default compression level is @samp{-6}, equivalent to @w{@samp{-s8MiB -m36}}. Note that @samp{-9} can be much slower than @samp{-0}. These options have no -effect when decompressing, testing or listing. +effect when decompressing, testing, or listing. The bidimensional parameter space of LZMA can't be mapped to a linear scale optimal for all files. If your files are large, very repetitive, -etc, you may need to use the @samp{--dictionary-size} and -@samp{--match-length} options directly to achieve optimal performance. +etc, you may need to use the options @samp{--dictionary-size} and +@samp{--match-length} directly to achieve optimal performance. If several compression levels or @samp{-s} or @samp{-m} options are given, the last setting is used. For example @w{@samp{-9 -s64MiB}} is @@ -394,7 +424,7 @@ equivalent to @w{@samp{-s64MiB -m273}} Aliases for GNU gzip compatibility. @item --loose-trailing -When decompressing, testing or listing, allow trailing data whose first +When decompressing, testing, or listing, allow trailing data whose first bytes are so similar to the magic bytes of a lzip header that they can be confused with a corrupt header. Use this option if a file triggers a "corrupt header" error and the cause is not indeed a corrupt header. @@ -411,6 +441,19 @@ decompressing to non-seekable output. Increasing the number of packets may increase decompression speed, but requires more memory. Valid values range from 1 to 1024. The default value is 64. +@item --check-lib +Compare the +@uref{http://www.nongnu.org/lzip/manual/lzlib_manual.html#Library-version,,version of lzlib} +used to compile plzip with the version actually being used at run time and +exit. Report any differences found. Exit with error status 1 if differences +are found. A mismatch may indicate that lzlib is not correctly installed or +that a different version of lzlib has been installed after compiling plzip. +@w{@samp{plzip -v --check-lib}} shows the version of lzlib being used and +the value of @samp{LZ_API_VERSION} (if defined). +@ifnothtml +@xref{Library version,,,lzlib}. +@end ifnothtml + @end table Numbers given as arguments to options may be followed by a multiplier @@ -438,16 +481,16 @@ caused plzip to panic. @node Program design -@chapter Program design +@chapter Internal structure of plzip @cindex program design -When compressing, plzip divides the input file into chunks and -compresses as many chunks simultaneously as worker threads are chosen, -creating a multimember compressed file. +When compressing, plzip divides the input file into chunks and compresses as +many chunks simultaneously as worker threads are chosen, creating a +multimember compressed file. When decompressing, plzip decompresses as many members simultaneously as worker threads are chosen. Files that were compressed with lzip will not -be decompressed faster than using lzip (unless the @samp{-b} option was used) +be decompressed faster than using lzip (unless the option @samp{-b} was used) because lzip usually produces single-member files, which can't be decompressed in parallel. @@ -492,6 +535,7 @@ when there is no longer anything to take away.@* @sp 1 In the diagram below, a box like this: + @verbatim +---+ | | <-- the vertical bars might be missing @@ -499,6 +543,7 @@ In the diagram below, a box like this: @end verbatim represents one byte; a box like this: + @verbatim +==============+ | | @@ -513,6 +558,7 @@ The members simply appear one after another in the file, with no additional information before, between, or after them. Each member has the following structure: + @verbatim +--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ID string | VN | DS | LZMA stream | CRC32 | Data size | Member size | @@ -532,8 +578,7 @@ Just in case something needs to be modified in the future. 1 for now. @anchor{coded-dict-size} @item DS (coded dictionary size, 1 byte) The dictionary size is calculated by taking a power of 2 (the base size) -and subtracting from it a fraction between 0/16 and 7/16 of the base -size.@* +and subtracting from it a fraction between 0/16 and 7/16 of the base size.@* Bits 4-0 contain the base 2 logarithm of the base size (12 to 29).@* Bits 7-5 contain the numerator of the fraction (0 to 7) to subtract from the base size to obtain the dictionary size.@* @@ -541,8 +586,8 @@ Example: 0xD3 = 2^19 - 6 * 2^15 = 512 KiB - 6 * 32 KiB = 320 KiB@* Valid values for dictionary size range from 4 KiB to 512 MiB. @item LZMA stream -The LZMA stream, finished by an end of stream marker. Uses default -values for encoder properties. +The LZMA stream, finished by an end of stream marker. Uses default values +for encoder properties. @ifnothtml @xref{Stream format,,,lzip}, @end ifnothtml @@ -553,7 +598,7 @@ See for a complete description. @item CRC32 (4 bytes) -CRC of the uncompressed original data. +Cyclic Redundancy Check (CRC) of the uncompressed original data. @item Data size (8 bytes) Size of the uncompressed original data. @@ -570,8 +615,8 @@ facilitates safe recovery of undamaged members from multimember files. @chapter Memory required to compress and decompress @cindex memory requirements -The amount of memory required @strong{per worker thread} for -decompression or testing is approximately the following: +The amount of memory required @strong{per worker thread} for decompression +or testing is approximately the following: @itemize @bullet @item @@ -610,8 +655,7 @@ times the data size. Default is @w{142 MiB}. @noindent The following table shows the memory required @strong{per thread} for -compression at a given level, using the default data size for each -level: +compression at a given level, using the default data size for each level: @multitable {Level} {Memory required} @item Level @tab Memory required @@ -643,7 +687,7 @@ least as large as the number of worker threads times the chunk size compress, and compression will be proportionally slower. The maximum speed increase achievable on a given file is limited by the ratio @w{(file_size / data_size)}. For example, a tarball the size of gcc or -linux will scale up to 8 processors at level -9. +linux will scale up to 10 or 14 processors at level -9. The following table shows the minimum uncompressed file size needed for full use of N processors at a given compression level, using the default @@ -723,7 +767,7 @@ where a file containing trailing data must be rejected, the option 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 -@samp{--keep} option to plzip and don't remove the original file until you +option @samp{--keep} to plzip and don't remove the original file until you verify the compressed file with a command like @w{@samp{plzip -cd file.lz | cmp file -}}. Most RAM errors happening during compression can only be detected by comparing the compressed file with the @@ -732,8 +776,18 @@ contents, resulting in a valid compressed file containing wrong data. @sp 1 @noindent -Example 1: Replace a regular file with its compressed version -@samp{file.lz} and show the compression ratio. +Example 1: Extract all the files from archive @samp{foo.tar.lz}. + +@example + tar -xf foo.tar.lz +or + plzip -cd foo.tar.lz | tar -xf - +@end example + +@sp 1 +@noindent +Example 2: Replace a regular file with its compressed version @samp{file.lz} +and show the compression ratio. @example plzip -v file @@ -741,8 +795,8 @@ plzip -v file @sp 1 @noindent -Example 2: Like example 1 but the created @samp{file.lz} has a block -size of @w{1 MiB}. The compression ratio is not shown. +Example 3: Like example 1 but the created @samp{file.lz} has a block size of +@w{1 MiB}. The compression ratio is not shown. @example plzip -B 1MiB file @@ -750,9 +804,8 @@ plzip -B 1MiB file @sp 1 @noindent -Example 3: Restore a regular file from its compressed version -@samp{file.lz}. If the operation is successful, @samp{file.lz} is -removed. +Example 4: Restore a regular file from its compressed version +@samp{file.lz}. If the operation is successful, @samp{file.lz} is removed. @example plzip -d file.lz @@ -760,8 +813,8 @@ plzip -d file.lz @sp 1 @noindent -Example 4: Verify the integrity of the compressed file @samp{file.lz} -and show status. +Example 5: Verify the integrity of the compressed file @samp{file.lz} and +show status. @example plzip -tv file.lz @@ -769,29 +822,31 @@ plzip -tv file.lz @sp 1 @noindent -Example 5: Compress a whole device in /dev/sdc and send the output to +Example 6: Compress a whole device in /dev/sdc and send the output to @samp{file.lz}. @example -plzip -c /dev/sdc > file.lz + plzip -c /dev/sdc > file.lz +or + plzip /dev/sdc -o file.lz @end example @sp 1 @anchor{concat-example} @noindent -Example 6: The right way of concatenating the decompressed output of two -or more compressed files. @xref{Trailing data}. +Example 7: The right way of concatenating the decompressed output of two or +more compressed files. @xref{Trailing data}. @example Don't do this - cat file1.lz file2.lz file3.lz | plzip -d + cat file1.lz file2.lz file3.lz | plzip -d - Do this instead plzip -cd file1.lz file2.lz file3.lz @end example @sp 1 @noindent -Example 7: Decompress @samp{file.lz} partially until @w{10 KiB} of +Example 8: Decompress @samp{file.lz} partially until @w{10 KiB} of decompressed data are produced. @example @@ -800,8 +855,8 @@ plzip -cd file.lz | dd bs=1024 count=10 @sp 1 @noindent -Example 8: Decompress @samp{file.lz} partially from decompressed byte -10000 to decompressed byte 15000 (5000 bytes are produced). +Example 9: Decompress @samp{file.lz} partially from decompressed byte at +offset 10000 to decompressed byte at offset 14999 (5000 bytes are produced). @example plzip -cd file.lz | dd bs=1000 skip=10 count=5 @@ -820,7 +875,7 @@ for all eternity, if not longer. If you find a bug in plzip, please send electronic mail to @email{lzip-bug@@nongnu.org}. Include the version number, which you can -find by running @w{@code{plzip --version}}. +find by running @w{@samp{plzip --version}}. @node Concept index |