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.
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.
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.
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.
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.
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.
- 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
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).
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.
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.
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.
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.
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.
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.
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.
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.