More at wikipedia. See the link at the bottom too.
The command-line options are deliberately very similar to those of GNU gzip.
Files on the command line (or expanded by globing) are replaced by a compressed version with the name suffixed by
Files are not over-written, specify
Piping is done if no file names are specified reading from standard input to writing to standard output (usefull to pipe elsewhere).
Decompresses specified files, unless they were not created by bzip2 which will be skipped with a warning.
If the file does not end in a recognised ending, .bz2, .bz, .tbz2 or .tbz, bzip2 warns that it cannot determine the name of the original file, and uses the original name with .out appended.
Given the concatenation of two or more compressed files produces the concatenation of the corresponding uncompressed files.
Integrity testing (
files re output to the standard output by using
Recovering data from damaged files:
bzip2, bunzip2 and bzcat are the same program, and the decision about what actions to take is done on the basis of which name is used.
Author Julian Seward, jsewardbzip.org. bzip.org:
gzip -l *gz compressed uncompressed ratio uncompressed_name 20 0 0.0% smother.diske- 20 0 0.0% smother.diskf- 20 0 0.0% smother.diskg- 20 0 0.0% smother.diskh- 798830592 3596346423 77.8% smother_wd0e 798830672 3596346423 77.8% (totals)with
gzip -lv *gz method crc date time compressed uncompressed ratio uncompressed_name defla 00000000 Sep 1 15:00 20 0 0.0% smother.diske- defla 00000000 Sep 1 15:01 20 0 0.0% smother.diskf- defla 00000000 Sep 1 15:01 20 0 0.0% smother.diskg- defla 00000000 Sep 1 15:01 20 0 0.0% smother.diskh- defla dbd673f2 Sep 1 16:09 798830592 3596346423 77.8% smother_wd0e 798830672 3596346423 77.8% (totals)The uncompressed size is given as
-1for files not in
gzipformat, such as compressed
zcat file.Z | wc -c
| || Travel the directory structure recursively. ||Suffix |
Most useful for decompression.
Any suffix can be given, but suffixes other than
A null suffix forces gunzip to try decompression on all given files regardless of suffix, as in:
gunzip -S "" * (*.* for MSDOS)Previous versions of gzip used the
| Test the compressed file integrity.
| Suppress all warning messages.
||Display the name and percentage reduction for each file ||
When compressing, do not save the original file name and time stamp by
default. (The original name is always saved if the name had to be truncated.) |
When decompressing, do not restore the original file name if present (remove only the
Default when decompressing.
When compressing, always save the original file name and time stamp (default).|
When decompressing, restore the original file name and time stamp. Useful on systems which have a limit on file name length.
Write output on standard output; keep original files unchanged.
If there are several input files, the output consists of a sequence of independently compressed members.
To obtain better compression, concatenate all input files before compressing them.
Specify speed/compression tradeoff |
|even if the file has multiple links
or the corresponding file already exists, or if the compressed data
is read from or written to a terminal. If the input data is not in
a format recognized by ||behave as ||Display the |
The following command will find all
gzip files in the current
directory and subdirectories, and extract them in place without
destroying the original:
find . -name '*.gz' -print | sed 's/^\(.*\)[.]gz$/gunzip < "&" > "\1"/' | sh
gunzipwill extract all members at once. If one member is damaged, other members might still be recovered after removal of the damaged member.
This is an example of concatenating
gzip --to-stdout file1 > foo.gz gzip --to-stdout file2 >> foo.gz
gunzip --to-stdout foo
cat file1 file2
In case of damage to one member of a
.gz file, other members can
still be recovered (if the damaged member is removed).
Better compression is obtained by compressing all members at once:
cat file1 file2 | gzip > foo.gz
compresses better than
gzip --to-stdout file1 file2 > foo.gz
To recompress concatenated files to get better compression:
zcat old.gz | gzip > new.gz
If a compressed file consists of several members, the uncompressed
size and CRC reported by the
--list option applies to the last member only.
To display the uncompressed size for all members, use:
zcat file.gz | wc -c
To create a single archive file with multiple members so
that members can later be extracted independently, use an archiver such
tar supports the
option to invoke
gzip is designed as a complement to
tar, not as a replacement.
$GZIPholds default options, interpreted first and can be overwritten by explicit command line parameters.
for sh: GZIP="-8v --name"; export GZIP for csh: setenv GZIP "-8v --name" for MSDOS: set GZIP=-8v --name
When writing compressed data to a tape, it is generally necessary to pad
the output with zeroes up to a block boundary.
When the data is read and the whole block is passed to
gunzip for decompression,
gunzip detects that there is extra trailing garbage after the
compressed data and emits a warning by default, use
--quiet to suppress the warning.
This option can be set in
$GZIP as in:
for sh: GZIP="-q" tar -xfz --block-compress /dev/rst0 for csh: (setenv GZIP "-q"; tar -xfz --block-compress /dev/rst0)
In the above example,
gzip is invoked implicitly by the
option of GNU
tar. Make sure that the same block size (
tar) is used for reading and writing compressed data on
tapes. (This example assumes you are using the GNU version of
gzip reduces the size using Lempel-Ziv coding
(LZ77) replacing a file by one with the extension
If no files are specified or if a file name is
- standard input is compressed to the standard
Only attempt to compress regular files ( symbolic links are ignored).
gzip keeps the original file name and timestamp in
the compressed file, which is used when decompressing the file with
gunzip takes a list of files on its command line and replaces each file whose name ends with
zcat is identical to
.gz suffix or not.
Apple gzip 272.250.1 usage: gzip [-123456789acdfhklLNnqrtVv] [-S .suffix] [www.bzip.org/1.0.5/bzip2-manual
[ ...]] -1 --fast fastest (worst) compression -2 .. -8 set compression level -9 --best best (slowest) compression -c --stdout write to stdout, keep original files --to-stdout -d --decompress uncompress files --uncompress -f --force force overwriting & compress links -h --help display this help -k --keep don't delete input files during operation -l --list list compressed file contents -N --name save or restore original file name and time stamp -n --no-name don't save original file name or time stamp -q --quiet output no warnings -r --recursive recursively compress files in directories -S .suf use suffix .suf instead of .gz --suffix .suf -t --test test compressed file -V --version display program version -v --verbose print extra statistics gzip --license Apple gzip 272.250.1 (based on FreeBSD gzip 20150113) Copyright (c) 1997, 1998, 2003, 2004, 2006 Matthew R. Green