Linux gzip Command
Learn Linux gzip Command with examples
Published
- Linux gzip Command
- gzip Command Syntax
- gzip Command Example
- gzip Compress multiple files
- gzip -k Command Example
- gzip -d Unzipping gz File
- gzip -dk Unzipping gz File keeping gzip file
- gzip -v Verbose output
- gzip -r Recursive Compress a Directory
- gzip -rd Recursive Decompress
- gzip Change the compression level
- gzip Check Compressed File Statistics
- gzip -c to Compress a Standard Input
- gzip -f forcefully overwrite to existing .gz file
- gzip Command in Linux (Documentation)
Linux gzip Command
Gzip is a file format as well as a software application which was created by Mark Adler and Jean-Loup Gailly and has been in use since the early Unix Systems.
In Linux we use “gzip” command to compresses only single files and creates a compressed file for each given file.
If you want to compress multiple files or directory into one file, you need to create a tar archive file and then compress the .tar file with Gzip.
File name after compressed with Gzip either .gz or .z
File name with .tar.gz or .tgz is a Tar archive file compressed with Gzip.
gzip Command Syntax
~$ gzip [OPTION]... [FILE]...
gzip Command Example
~$ gzip file1.txt
~$ gzip mydocument.txt
# These commands will create file1.txt.gz and mydocument.txt.gz compress files. However, the original files like file1.txt and mydocument.txt will be removed.
gzip Compress multiple files
You can also pass multiple files as arguments to gzip command.
gzip content1 content2 content3
# The command above will create three compressed files, content1.gz, content2.gz, content3.gz.
gzip -k Command Example
gzip -k keep the original file and create a new gzip file.
~$ gzip -k file1.txt
# gzip -k keep original file and create a new gzip file.
gzip -d Unzipping gz File
gzip -d can decompress a .gz file using the gzip utility.
~$ gzip -d file1.gz
Another command that you can use to decompress a .gz file is gunzip This command is basically an alias to file with gzip -d.
To open a .gz file with gunzip simply pass the file name to the command:
~$ gunzip file.gz
gzip -dk Unzipping gz File keeping gzip file
To keep the compressed file pass the -k option to the command. This will keep the gzip file as well as unzip using -d.
gzip -dk file.gz
gzip -v Verbose output
Use the -v option if you want to see the percentage reduction and the names of the files that are being processed.
~$ gzip -v filename
# filename: 8.5% -- replaced with filename.gz
gzip -r Recursive Compress a Directory
gzip -r option will descend into the directory and compress all the files it finds there.
~$ gzip -r mywebsites
# gzip -r will compress will files inside the mywebsite folder.
gzip -rd Recursive Decompress
~$ gzip -rd mywebsites
# gzip -rd will decompress will files inside the mywebsite folder.
gzip Change the compression level
gzip provides a range of compression levels, from 1 to 9. -1 or –fast means fastest compression speed with minimal compression ratio, -9 or –best indicates the slowest compression speed with maximum compression ratio. The default compression level is -6.
gzip -9 filename
# For example, to get maximum compression we can run gzip -9 filename.
# Compression is a CPU-intensive task, the higher the compression level, the longer the process takes.
gzip Check Compressed File Statistics
Use gzip -l to see compressed and uncompressed file sizes would be. gzip -l shows statistics about the given compressed files.
~# gzip -l filename.gz
~$ gzip -lv filename.gz
# -v for verbose
gzip -c to Compress a Standard Input
To create a .gz file from the standard input (stdin), pipe the output of the command to gzip. Let’s Create a Gzipped MySQL database backup.
~$ mysqldump mysql_database_name | gzip -c > mysql_database_name.sql.gz
# The output of the mysqldump command will be input for gzip.
gzip -f forcefully overwrite to existing .gz file
If gz compress file already exist and you just want to overwrite it without asking Y/N confirmation then you can use gzip -f.
~$ gzip -f filename
# gzip -f forcefully overwrite to existing
gzip Command in Linux (Documentation)
NAME
gzip, gunzip, zcat - compress or expand files
SYNOPSIS
gzip [ -acdfhklLnNrtvV19 ] [-S suffix] [ name ... ]
gunzip [ -acfhklLnNrtvV ] [-S suffix] [ name ... ]
zcat [ -fhLV ] [ name ... ]
DESCRIPTION
Gzip reduces the size of the named files using Lempel-Ziv coding
(LZ77). Whenever possible, each file is replaced by one with the
extension .gz, while keeping the same ownership modes, access and
modification times. (The default extension is z for MSDOS, OS/2
FAT, Windows NT FAT and Atari.) If no files are specified, or if
a file name is "-", the standard input is compressed to the stan‐
dard output. Gzip will only attempt to compress regular files.
In particular, it will ignore symbolic links.
If the compressed file name is too long for its file system, gzip
truncates it. Gzip attempts to truncate only the parts of the
file name longer than 3 characters. (A part is delimited by
dots.) If the name consists of small parts only, the longest parts
are truncated. For example, if file names are limited to 14 char‐
acters, gzip.msdos.exe is compressed to gzi.msd.exe.gz. Names are
not truncated on systems which do not have a limit on file name
length.
By default, gzip keeps the original file name and timestamp in the
compressed file. These are used when decompressing the file with
the -N option. This is useful when the compressed file name was
truncated or when the timestamp was not preserved after a file
transfer.
Compressed files can be restored to their original form using gzip
-d or gunzip or zcat. If the original name saved in the com‐
pressed file is not suitable for its file system, a new name is
constructed from the original one to make it legal.
gunzip takes a list of files on its command line and replaces each
file whose name ends with .gz, -gz, .z, -z, or _z (ignoring case)
and which begins with the correct magic number with an uncom‐
pressed file without the original extension. gunzip also recog‐
nizes the special extensions .tgz and .taz as shorthands for
.tar.gz and .tar.Z respectively. When compressing, gzip uses the
.tgz extension if necessary instead of truncating a file with a
.tar extension.
gunzip can currently decompress files created by gzip, zip, com‐
press, compress -H or pack. The detection of the input format is
automatic. When using the first two formats, gunzip checks a 32
bit CRC. For pack and gunzip checks the uncompressed length. The
standard compress format was not designed to allow consistency
checks. However gunzip is sometimes able to detect a bad .Z file.
If you get an error when uncompressing a .Z file, do not assume
that the .Z file is correct simply because the standard uncompress
does not complain. This generally means that the standard uncom‐
press does not check its input, and happily generates garbage out‐
put. The SCO compress -H format (lzh compression method) does not
include a CRC but also allows some consistency checks.
Files created by zip can be uncompressed by gzip only if they have
a single member compressed with the 'deflation' method. This fea‐
ture is only intended to help conversion of tar.zip files to the
tar.gz format. To extract a zip file with a single member, use a
command like gunzip <foo.zip or gunzip -S .zip foo.zip. To ex‐
tract zip files with several members, use unzip instead of gunzip.
zcat is identical to gunzip -c. (On some systems, zcat may be in‐
stalled as gzcat to preserve the original link to compress.) zcat
uncompresses either a list of files on the command line or its
standard input and writes the uncompressed data on standard out‐
put. zcat will uncompress files that have the correct magic num‐
ber whether they have a .gz suffix or not.
Gzip uses the Lempel-Ziv algorithm used in zip and PKZIP. 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 reduced by 60-70%. Compression is
generally much better than that achieved by LZW (as used in com‐
press), Huffman coding (as used in pack), or adaptive Huffman cod‐
ing (compact).
Compression is always performed, even if the compressed file is
slightly larger than the original. The worst case expansion is a
few bytes for the gzip file header, plus 5 bytes every 32K block,
or an expansion ratio of 0.015% for large files. Note that the ac‐
tual number of used disk blocks almost never increases. gzip pre‐
serves the mode, ownership and timestamps of files when compress‐
ing or decompressing.
OPTIONS
-a --ascii
Ascii text mode: convert end-of-lines using local conven‐
tions. This option is supported only on some non-Unix sys‐
tems. For MSDOS, CR LF is converted to LF when compressing,
and LF is converted to CR LF when decompressing.
-c --stdout --to-stdout
Write output on standard output; keep original files un‐
changed. If there are several input files, the output con‐
sists of a sequence of independently compressed members. To
obtain better compression, concatenate all input files be‐
fore compressing them.
-d --decompress --uncompress
Decompress.
-f --force
Force compression or decompression 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 termi‐
nal. If the input data is not in a format recognized by
gzip, and if the option --stdout is also given, copy the
input data without change to the standard output: let zcat
behave as cat. If -f is not given, and when not running in
the background, gzip prompts to verify whether an existing
file should be overwritten.
-h --help
Display a help screen and quit.
-k --keep
Keep (don't delete) input files during compression or de‐
compression.
-l --list
For each compressed file, list the following fields:
compressed size: size of the compressed file
uncompressed size: size of the uncompressed file
ratio: compression ratio (0.0% if unknown)
uncompressed_name: name of the uncompressed file
The uncompressed size is given as -1 for files not in gzip
format, such as compressed .Z files. To get the uncom‐
pressed size for such a file, you can use:
zcat file.Z | wc -c
In combination with the --verbose option, the following
fields are also displayed:
method: compression method
crc: the 32-bit CRC of the uncompressed data
date & time: timestamp for the uncompressed file
The compression methods currently supported are deflate,
compress, lzh (SCO compress -H) and pack. The crc is given
as ffffffff for a file not in gzip format.
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, unless some sizes are unknown.
With --quiet, the title and totals lines are not displayed.
-L --license
Display the gzip license and quit.
-n --no-name
When compressing, do not save the original file name and
timestamp 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
gzip suffix from the compressed file name) and do not re‐
store the original timestamp if present (copy it from the
compressed file). This option is the default when decom‐
pressing.
-N --name
When compressing, always save the original file name and
timestamp; this is the default. When decompressing, restore
the original file name and timestamp if present. This op‐
tion is useful on systems which have a limit on file name
length or when the timestamp has been lost after a file
transfer.
-q --quiet
Suppress all warnings.
-r --recursive
Travel the directory structure recursively. If any of the
file names specified on the command line are directories,
gzip will descend into the directory and compress all the
files it finds there (or decompress them in the case of
gunzip ).
-S .suf --suffix .suf
When compressing, use suffix .suf instead of .gz. Any non-
empty suffix can be given, but suffixes other than .z and
.gz should be avoided to avoid confusion when files are
transferred to other systems.
When decompressing, add .suf to the beginning of the list
of suffixes to try, when deriving an output file name from
an input file name.
--synchronous
Use synchronous output. With this option, gzip is less
likely to lose data during a system crash, but it can be
considerably slower.
-t --test
Test. Check the compressed file integrity.
-v --verbose
Verbose. Display the name and percentage reduction for each
file compressed or decompressed.
-V --version
Version. Display the version number and compilation options
then quit.
-# --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 -6 (that is, biased towards high com‐
pression at expense of speed).
--rsyncable
When you synchronize a compressed file between two comput‐
ers, this option allows rsync to transfer only files that
were changed in the archive instead of the entire archive.
Normally, after a change is made to any file in the ar‐
chive, the compression algorithm can generate a new version
of the archive that does not match the previous version of
the archive. In this case, rsync transfers the entire new
version of the archive to the remote computer. With this
option, rsync can transfer only the changed files as well
as a small amount of metadata that is required to update
the archive structure in the area that was changed.
ADVANCED USAGE
Multiple compressed files can be concatenated. In this case, gun‐
zip will extract all members at once. For example:
gzip -c file1 > foo.gz
gzip -c file2 >> foo.gz
Then
gunzip -c foo
is equivalent to
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). However,
you can get better compression by compressing all members at once:
cat file1 file2 | gzip > foo.gz
compresses better than
gzip -c file1 file2 > foo.gz
If you want to recompress concatenated files to get better com‐
pression, do:
gzip -cd 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. If you need the uncompressed size for all members,
you can use:
gzip -cd file.gz | wc -c
If you wish to create a single archive file with multiple members
so that members can later be extracted independently, use an
archiver such as tar or zip. GNU tar supports the -z option to in‐
voke gzip transparently. gzip is designed as a complement to tar,
not as a replacement.