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1998-04-27
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NAME
lzop - compress or expand files
ABSTRACT
lzop is a file compressor very similar to gzip. lzop favors
speed over compression ratio.
SYNOPSIS
lzop [ *command* ] [ *options* ] [ *filename* ... ]
lzop [-dxlthIVL19] [-qvcfFnNkU] [-o *file*] [-p[*path*]] [-S
*suffix*] [*filename* ...]
DESCRIPTION
lzop reduces the size of the named files. Whenever possible,
each file is compressed into one with the extension .lzo, while
keeping the same ownership modes, access and modification times.
If no files are specified, or if a file name is "-", lzop tries
to compress the standard input to the standard output. lzop will
only attempt to compress regular files. In particular, it will
ignore directories and symbolic links.
If the compressed file name is too long for its file system,
lzop truncates it.
Compressed files can be restored to their original form using
lzop -d. lzop -d takes a list of files on its command line and
decompresses each file whose name ends with .lzo and which
begins with the correct magic number to an uncompressed file
without the original extension. lzop -d also recognizes the
special extension .tzo as shorthand for .tar.lzo. When
compressing, lzop uses the .tzo extension if necessary instead
of truncating a file with a .tar extension.
lzop stores the original file name, mode and time stamp in the
compressed file. These can be used when decompressing the file
with the -d option. This is useful when the compressed file name
was truncated or when the time stamp was not preserved after a
file transfer.
lzop preserves the ownership, mode and time stamp of files when
compressing. When decompressing lzop restores the mode and time
stamp if present in the compressed files. See the options -n, -
N, --no-mode and --no-time for more information.
lzop always keeps original files unchanged unless you use the
option -U.
lzop uses the *LZO data compression library* for compression
services. The amount of compression obtained depends on the size
of the input and the distribution of common substrings.
Typically, text such as source code or English is compressed
into 40-50% of the original size, and large files usually
compress much better than small ones. Compression and
decompression speed is generally much faster than that achieved
by gzip, but compression ratio is worse.
COMPRESSION LEVELS
lzop offers the following compression levels of the LZO1X
algorithm:
-3 the default level offers pretty fast compression. Note that -2,
-3, -4, -5 and -6 are currently all equivalent - this may
change in a future release.
-1, --fast
can be even a little bit faster in some cases - but most
times you won't notice the difference
-7, -8, -9, --best
these compression levels are mainly intended for generating
pre-compressed data - especially -9 can be somewhat slow
Decompression is *very* fast for all compression levels.
MAIN COMMAND
If no other command is given then lzop defaults to compression.
-#, --fast, --best
Regulate the speed of compression using the specified digit
#, where -1 or --fast indicates the fastest compression
method (less compression) and -9 or --best indicates the
slowest compression method (best compression). The default
compression level is -3.
-d, --decompress, --uncompress
Decompress. Each file will be placed into same the directory
as the compressed file.
-x, --extract
Extract compressed files to the current working directory.
This is the same as `-dNp'.
-t, --test
Test. Check the compressed file integrity.
-l, --list
For each compressed file, list the following fields:
method: compression method
compressed: size of the compressed file
uncompr.: size of the uncompressed file
ratio: compression ratio
uncompressed_name: name of the uncompressed file
In combination with the --verbose option, the following
fields are also displayed:
date & time: time stamp for the uncompressed file
With --name, the uncompressed name, date and time are those
stored within the compress file if present.
With --verbose, the size totals and compression ratio for
all files is also displayed. With --quiet, the title and
totals lines are not displayed.
Note that lzop defines compression ratio as compressed_size
/ uncompressed_size.
--ls, --ls=*FLAGS*
List each compressed file in a format similar to ls -ln.
The following flags are currently honoured: F Append a `*'
for executable files. G Inhibit display of group
information. Q Enclose file names in double quotes.
--info
For each compressed file, list the internal header fields.
-I, --sysinfo
Display information about the system and quit.
-L, --license
Display the lzop license and quit.
-h, -H, --help
Display a help screen and quit.
-V Version. Display the version number and compilation options then
quit.
--version
Version. Display the version number then quit.
Note that -t has priority over -d, -l over -t, and so on.
OPTIONS
-c, --stdout, --to-stdout
Write output on standard output. If there are several input
files, the output consists of a sequence of independently
(de)compressed members. To obtain better compression,
concatenate all input files before compressing them.
-o *FILE*, --output=*FILE*
Write output to the file *FILE*. If there are several input
files, the output consists of a sequence of independently
(de)compressed members.
-p, -p*DIR*, --path=*DIR*
Write output files into the directory *DIR* instead of the
directory determined by the input file. If *DIR* is omitted,
then write to the current working directory.
-f, --force
Force lzop to
- overwrite existing files
- compress from stdin even if it seems a terminal
- compress to stdout even if it seems a terminal
- allow option -c in combination with -U
Using -f two or more times forces things like
- compress files that already have a .lzo suffix
- decompress files that do not have a valid suffix
- try to handle compressed files with unknown header flags
Use with care.
-F, --no-checksum
Do not store or verify a checksum of the uncompressed file
when compressing or decompressing. This speeds up the
operation of lzop a little bit (especially when
decompressing), but as unnoticed data corruption can happen
in case of damaged compressed files the usage of this option
is not generally recommended. Also, a checksum is always
stored when compressing with one of the slow compression
levels (-7, -8 or -9).
-n, --no-name
When decompressing, do not restore the original file name if
present (remove only the lzop suffix from the compressed
file name). This option is the default under UNIX.
-N, --name
When decompressing, restore the original file name if
present. This option is useful on systems which have a limit
on file name length. If the original name saved in the
compressed file is not suitable for its file system, a new
name is constructed from the original one to make it legal.
This option is the default under DOS, Windows and OS/2.
--no-mode
When decompressing, do not restore the original mode
(permissions) saved in the compressed file.
--no-time
When decompressing, do not restore the original time stamp
saved in the compressed file.
-S *.suf*, --suffix=*.suf*
Use suffix *.suf* instead of *.lzo*. The suffix must not
contain multiple dots and special characters like '+' or
'*', and suffixes other than *.lzo* should be avoided to
avoid confusion when files are transferred to other systems.
-k, --keep
Do not delete input files. This is the default.
-U, --unlink, --delete
Delete input files after succesfull compression or
decompression. Beware. Use this option to make lzop behave
like gzip. Note that -k overrides -U.
--no-stdin
Do not try to read standard input. This option is necessary
in cron jobs (which do not have a controlling terminal). A
file name "-" will still override this option.
--no-warn
Suppress all warnings.
--ignore-warn
Suppress all warnings, and never exit with exit status 2.
-q, --quiet, --silent
Suppress all warnings and decrease the verbosity of some
commands like --list or --test.
-v, --verbose
Verbose. Display the name for each file compressed or
decompressed. Multiple -v can be used to increase the
verbosity of some commands like --list or --test.
-- Specifies that this is the end of the options. Any file name
after -- will not be interpreted as an option even if it
starts with a hyphen.
OTHER OPTIONS
--no-color
Do not use any color escape sequences.
--mono
Assume a mono ANSI terminal. This is the default under UNIX.
--color
Assume a color ANSI terminal or try full-screen access. This
is the default under DOS and in a Linux virtual console.
--intro
Try to display that nice intro sequence then quit. Needs
full-screen access.
--filter=*NUMBER*
Rarely useful. Preprocess data with a special "multimedia"
filter before compressing in order to improve compression
ratio. *NUMBER* must be a decimal number from 1 to 16,
inclusive. Using a filter slows down both compression and
decompression quite a bit, and the compression ratio usually
doesn't improve much either... More effective filters may be
added in the future, though.
You can try --filter=1 with data like 8-bit sound samples, -
-filter=2 with 16-bit samples or depth-16 images, etc.
Un-filtering during decompression is handled automatically.
-C, --checksum
Deprecated. Only for compatibility with old versions as lzop
now uses a checksum by default. This option may get removed
in a future release.
ADVANCED USAGE
lzop allows you to deal with your files in many flexible ways.
Here are some usage examples:
single file mode: individually (de)compress each file
create
lzop a.c -> create a.c.lzo
lzop a.c b.c -> create a.c.lzo & b.c.lzo
lzop -U a.c b.c -> create a.c.lzo & b.c.lzo and delete a.c & b.c
lzop *.c
extract
lzop -d a.c.lzo -> restore a.c
lzop -df a.c.lzo -> restore a.c, overwrite if already exists
lzop -d *.lzo
list
lzop -l a.c.lzo
lzop -l *.lzo
lzop -lv *.lzo -> be verbose
test
lzop -t a.c.lzo
lzop -tq *.lzo -> be quiet
pipe mode: (de)compress from stdin to stdout
create
lzop < a.c > y.lzo
cat a.c | lzop > y.lzo
tar -cf - *.c | lzop > y.tar.lzo -> create a compressed tar file
extract
lzop -d < y.lzo > a.c
lzop -d < y.tar.lzo | tar -xvf - -> extract a tar file
lzop -d < y.tar.lzo | tar -tvf - -> list a tar file
list
lzop -l < y.lzo
cat y.lzo | lzop -l
test
lzop -t < y.lzo
cat y.lzo | lzop -t
stdout mode: (de)compress to stdout
create
lzop -c a.c > y.lzo
extract
lzop -dc y.lzo > a.c
lzop -dc y.tar.lzo | tar -tvf - -> list a tar file
archive mode: compress/extract multiple files into a single archive file
create
lzop a.c b.c -o sources.lzo -> create an archive
lzop -c *.c > sources.lzo -> another way to create an archive
lzop -c *.h >> sources.lzo -> add files to archive
extract
lzop -dN sources.lzo
lzop -x ../src/sources.lzo -> extract to current directory
lzop -x -p/tmp < ../src/sources.lzo -> extract to /tmp directory
list
lzop -lNv sources.lzo
test
lzop -t sources.lzo
lzop -tvv sources.lzo -> be very verbose
If you wish to create a single archive file with multiple
members so that members can later be extracted independently,
you should prefer a full-featured archiver such as tar or zip.
The latest version of GNU tar supports the --use-compress-
program=lzop option to invoke lzop transparently. lzop is
designed as a complement to tar, not as a replacement.
ENVIRONMENT
The environment variable LZOP can hold a set of default options
for lzop. These options are interpreted first and can be
overwritten by explicit command line parameters. For example:
for sh/ksh/zsh: LZOP="-1v --name"; export LZOP
for csh/tcsh: setenv LZOP "-1v --name"
for DOS: set LZOP=-1v --name
On Vax/VMS, the name of the environment variable is LZOP_OPT, to
avoid a conflict with the symbol set for invocation of the
program.
Note that not all options are valid in the environment variable
- lzop will tell you.
SEE ALSO
gzip(1), tar(1), bzip2(1)
Precompiled binaries for some platforms should be available from
the lzop home page soon.
see http://wildsau.idv.uni-linz.ac.at/mfx/lzop.html
lzop uses the LZO data compression library for compression
services.
see http://wildsau.idv.uni-linz.ac.at/mfx/lzo.html
DIAGNOSTICS
Exit status is normally 0; if an error occurs, exit status is 1.
If a warning occurs, exit status is 2.
lzop's diagnostics are intended to be self-explanatory.
BUGS
Please report all bugs immediately to the author.
AUTHOR
markus.oberhumer@jk.uni-linz.ac.at
COPYRIGHT
lzop and the LZO library are Copyright (C) 1996, 1997, 1998 by
Markus Franz Xaver Johannes Oberhumer.
lzop and the LZO library are distributed under the terms of the
GNU General Public License (GPL).