pigz(1) - NetBSD Manual Pages

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PIGZ(1)                 NetBSD General Commands Manual                 PIGZ(1)


NAME

     pigz, unpigz -- compress or expand files


SYNOPSIS

     pigz [-0..9cdFfhiKkLlNnqORrTtz] [-11] [-b blocksize] [-I iterations]
          [-M maxsplits] [-p threads] [-S suffix] [file ...]
     unpigz [-cfhiKkLlNnqRrTtz] [-b blocksize] [-p threads] [-S suffix]
          [file ...]


DESCRIPTION

     pigz compresses using threads to make use of multiple processors and
     cores.  The input is broken up into 128 KB chunks with each compressed in
     parallel.  The individual check value for each chunk is also calculated
     in parallel.  The compressed data is written in order to the output, and
     a combined check value is calculated from the individual check values.

     The compressed data format generated is in the gzip, zlib, or single-
     entry zip format using the deflate compression method.  The compression
     produces partial raw deflate streams which are concatenated by a single
     write thread and wrapped with the appropriate header and trailer, where
     the trailer contains the combined check value.

     Each partial raw deflate stream is terminated by an empty stored block
     (using the Z_SYNC_FLUSH option of zlib(3)), in order to end that partial
     bit stream at a byte boundary.  That allows the partial streams to be
     concatenated simply as sequences of bytes.  This adds a very small four
     to five byte overhead to the output for each input chunk.

     The default input block size is 128K, but can be changed with the -b
     option.  The number of compress threads is set by default to the number
     of online processors, which can be changed using the -p option.  Specify-
     ing -p 1 avoids the use of threads entirely.

     The input blocks, while compressed independently, have the last 32K of
     the previous block loaded as a preset dictionary to preserve the compres-
     sion effectiveness of deflating in a single thread.  This can be turned
     off using the -i or --independent option, so that the blocks can be
     decompressed independently for partial error recovery or for random
     access.

     Decompression can't be parallelized, at least not without specially pre-
     pared deflate streams for that purpose.  As a result, pigz uses a single
     thread (the main thread) for decompression, but will create three other
     threads for reading, writing, and check calculation, which can speed up
     decompression under some circumstances.  Parallel decompression can be
     turned off by specifying one process (-dp 1 or -tp 1).

     Compressed files can be restored to their original form using pigz -d or
     unpigz.


OPTIONS

     -#, --fast, --best   Regulate the speed of compression using the speci-
                          fied digit #, where -1 or --fast indicates the
                          fastest compression method (less compression) and -9
                          or --best indicates the slowest compression method
                          (best compression).  -0 is no compression.  -11
                          gives a few percent better compression at a severe
                          cost in execution time.  The default is -6.

     -b, --blocksize mmm  Set compression block size to mmm K (default
                          128KiB).

     -c, --stdout, --to-stdout
                          Write all processed output to stdout (won't delete).

     -d, --decompress, --uncompress
                          Decompress the compressed input.

     -F, --first          If compressing at level 11, do iterations first,
                          before block split (default is last).

     -f, --force          Force overwrite, compress .gz, links, and to termi-
                          nal.

     -h, --help           Display a help screen and quit.

     -I, --iterations n   If compressing at level 11, number of iterations for
                          optimization (default 15).

     -i, --independent    Compress blocks independently for damage recovery.

     -K, --zip            Compress to PKWare zip (.zip) single entry format.

     -k, --keep           Do not delete original file after processing.

     -L, --license        Display the pigz license and quit.

     -l, --list           List the contents of the compressed input.

     -M, --maxsplits n    If compressing at level 11, maximum number of split
                          blocks (default 15).

     -N, --name           Store/restore file name and mod time in/from header.

     -n, --no-name        Do not store or restore file name in/from header.

     -O, --oneblock       If compressing at level 11, do not split into
                          smaller blocks (default is block splitting).

     -p, --processes n    Allow up to n processes (default is the number of
                          online processors)

     -q, --quiet, --silent
                          Print no messages, even on error.

     -R, --rsyncable      Input-determined block locations for rsync.

     -r, --recursive      Process the contents of all subdirectories.

     -S, --suffix .sss    Use suffix .sss instead of .gz (for compression).

     -T, --no-time        Do not store or restore mod time in/from header.

     -t, --test           Test the integrity of the compressed input.

     -V, --version        Show the version of pigz.

     -v, --verbose        Provide more verbose output.

     -z, --zlib           Compress to zlib (.zz) instead of gzip format.


COPYRIGHT NOTICE

     This software is provided 'as-is', without any express or implied war-
     ranty.  In no event will the author be held liable for any damages aris-
     ing from the use of this software.

     Copyright (C) 2007, 2008, 2009, 2010 Mark Adler
     <madler@alumni.caltech.edu>

NetBSD 10.99                     June 15, 2014                    NetBSD 10.99