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lbzip2

NAME

lbzip2 - parallel bzip2 utility

SYNOPSIS

lbzip2|bzip2 [-n WTHRS] [-k|-c|-t] [-d] [-1 .. -9] [-f] [-v] [-S] [ FILE ... ]

lbunzip2|bunzip2 [-n WTHRS] [-k|-c|-t] [-z] [-f] [-v] [-S] [ FILE ... ]

lbzcat|bzcat [-n WTHRS] [-z] [-f] [-v] [-S] [ FILE ... ]

lbzip2|bzip2|lbunzip2|bunzip2|lbzcat|bzcat -h

DESCRIPTION

Compress or decompress FILE operands or standard input to regular files or standard output, by calling Julian Seward's libbz2 from multiple threads. The lbzip2 utility employs multiple threads and an input-bound splitter even when decompressing .bz2 files created by standard bzip2 (but see BUGS below).

INVOCATION

The default mode of operation is compression. If the utility is invoked as lbunzip2 or bunzip2, the MO is switched to decompression. Calling the utility as lbzcat or bzcat selects decompression, with the decompressed byte-stream written to standard output.

OPTIONS

-n WTHRS

Set the number of (de)compressor threads to WTHRS. If this option is not specified, lbzip2 either queries the system for the number of online processors (if both the compilation environment and the execution environment support that), or it exits with an error.

-k, --keep

Don't remove FILE operands after successful (de)compression. Open regular input files with more than one links.

-c, --stdout

Write output to standard output, even when FILE operands are present. Implies -k and excludes -t.

-t, --test

Test decompression; discard output instead of writing it to files or standard output. Implies -k and excludes -c.

-d, --decompress

Force decompression over the mode of operation selected by the invocation name.

-z, --compress

Force compression over the mode of operation selected by the invocation name.

-1 .. -9

Set the compression block size to 100K .. 900K, in 100K increments.

--fast

Alias for -1.

--best

Alias for -9. This is the default.

-f, --force

Open non-regular input files. Open input files with more than one links, breaking links when -k isn't specified in addition. Try to remove each output file before opening it.

-v, --verbose

Print a short message to standard error whenever a (de)compression operation commences.

-S

Print condition variable statistics to standard error for each completed (de)compression operation.

-s, --small, -q, --quiet, --repetitive-fast, --repetitive-best

Accepted for compatibility with bzip2, otherwise ignored.

-h, --help, -L, --license, -V, --version

Display license and version information, plus help on command-line usage.

ENVIRONMENT

LBZIP2, BZIP2, BZIP

Before parsing the command line, lbzip2 inserts the contents of these variables, in the order specified, between the invocation name and the rest of the command line. Tokens are separated by spaces and tabs, which cannot be escaped.

LBZIP2_TRACE_ALLOC

If this variable is set to a non-empty value, lbzip2 prints a memory allocation trace to standard error. The trace can be checked with the /usr/share/lbzip2/malloc_trace.pl Perl script.

OPERANDS

FILE

Specify files to compress or decompress. If no FILE is given, lbzip2 works as a filter. FILEs with .bz2, .tbz, .tbz2 and .tz2 name suffixes will be skipped when compressing. When decompressing, .bz2 suffixes will be removed in output filenames; .tbz, .tbz2 and .tz2 suffixes will be replaced by .tar; other filenames will be suffixed with .out. If an INT or TERM signal is delivered to lbzip2, then it removes the regular output file currently open before exiting.

EXIT STATUS

0

if lbzip2 finishes successfully. This presumes that whenever it tries, lbzip2 never fails to write to standard error.

1

if lbzip2 encounters a fatal error.

4

if lbzip2 issues warnings without encountering a fatal error. This presumes that whenever it tries, lbzip2 never fails to write to standard error.

SIGPIPE, SIGXFSZ

if lbzip2 intends to exit with status 1 due to any fatal error, but any such signal with inherited SIG_DFL action was generated for lbzip2 previously, then lbzip2 terminates by way of one of said signals, after cleaning up any interrupted output file.

SIGABRT

(via assert()) if a runtime assertion fails (ie. lbzip2 detects a bug in itself). Hopefully whoever compiled your binary wasn't bold enough to #define NDEBUG.

SIGINT, SIGTERM

lbzip2 catches these signals so that it can remove an interrupted output file. In such cases, lbzip2 exits by re-raising (one of) the received signal(s).

BUGS

The compressed output is a sequence of single-block bzip2 streams, instead of being a single multi-block bzip2 stream. Thus no output-global combined CRC can be written, and the resulting .bz2 file will return multiple BZ_STREAM_ENDs when decompressed with libbz2.

The multiple-workers decompressor (lbzip2 -d -n WTHRS, where WTHRS is greater than 1, either by default or by manual selection) doesn't check stream-level (combined) CRCs, only block-level CRCs. It can also fail to decompress some rare valid .bz2 files. (See the Bugs section of the /usr/share/doc/lbzip2/README file for more on this.) Since the author cannot rule out that such a failure may get reported as corrupt input instead of the dedicated error message, lbzip2 doesn't reserve a separate exit status for corrupt input -- it could be misleading.

The bit-string search algorithm used in the multiple-workers decompressor is naive and slow.

Separate input files don't share worker threads; at most one input file is worked on at any moment.

AUTHOR

Written by Laszlo Ersek <lacos@caesar.elte.hu>, http://lacos.hu/.

COPYRIGHT

Copyright (C) 2008, 2009, 2010 Laszlo Ersek.

This is free software. You may redistribute copies of it under the terms of the GNU General Public License, version 2:

http://www.gnu.org/licenses/gpl-2.0.html

or -- at your opinion -- any later version, eg.

http://www.gnu.org/licenses/gpl.html

THANKS

Adam Maulis at ELTE IIG; Julian Seward; Paul Sladen; Michael Thomas from Caltech HEP; Bryan Stillwell; Zsolt Bartos-Elekes; Imre Csatlos; Gabor Kovesdan; Paul Wise; Paolo Bonzini; Department of Electrical and Information Engineering at the University of Oulu.

SEE ALSO

bzip2(1)

http://www.bzip.org/

pbzip2(1)

http://compression.ca/pbzip2/

bzip2smp(1)

http://bzip2smp.sourceforge.net/

smpbzip2(1)

http://home.student.utwente.nl/n.werensteijn/smpbzip2/

dbzip2(1)

http://www.mediawiki.org/wiki/Dbzip2

p7zip(1)

http://p7zip.sourceforge.net/