Linux / Unix Command: gzip
• gzip is a fast and efficient compression
– .gz filename extension
– gzip test.txt
• By default, gzip keeps the original file
name and timestamp in the compressed
• gzip [ -acdfhlLnNrtvV19 ] [-S suffix] [ name ... ]
• gunzip [ -acfhlLnNrtvV ] [-S suffix] [ name ... ]
• zcat [ -fhLV ] [ name ... ]
• gunzip also recognizes the special
extensions .tgz and .taz as shorthands
for .tar.gz and .tar.Z respectively.
• -c --stdout --to-stdout
– Write output on standard output
– keeps original files unchanged.
– If there are several input files, the output
consists of a sequence of independently
• -f –force
– Force compression or decompression even if
the file has multiple links or the corresponding
file already exists
• -l –list
– For each compressed file, list the following
• 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
• -n --no-name
– When compressing, do not save the original file
name and time stamp by default.
– When decompressing, do not restore the original
file name if present (remove only the gzip suffix
from the compressed file name) and do not restore
the original time stamp if present.
• -N –name
– When compressing, always save the original file
name and time stamp
– this is the default!
• -r –recursive
– Travel the directory structure recursively
• -t –test
– Test : Check the compressed file integrity.
• -# --fast –best
– Regulate the speed of compression using the
specified digit #
• -1 or --fast
– indicates the fastest compression method
– less compression
• -9 or --best
– indicates the slowest compression method
– best compression
• The default compression level is-6
• That is, biased towards high compression at
expense of speed
• Compressed files can be restored to their
original form using:
– gzip -d oror
– gunzip oror
• gunzip can currently decompress files created
by gzip, zip, compress, compress -H or pack.
– The detection of the input format is automatic.
• gzip and gunzip can also compress or
decompress data from standard input and
– ls -laR $HOME | gzip > filelist.gz
– Or by using –c option
• bzip2, bunzip2
– a block-sorting file compressor, v1.0.2
– decompresses files to stdout
– recovers data from damaged bzip2 files
• on the average about 10-20% better than
– at the expense of longer compression times
• Output with .bz2 filename extension
• bzip2 [ -cdfkqstvzVL123456789 ] [ filenames ... ]
• bunzip2 [ -fkvsVL ] [ filenames ... ]
• bzcat [ -s ] [ filenames ... ]
• bzip2recover filename
• Each file is replaced by a compressed version of
itself, with the name "original_name.bz2“
• -c –stdout
– (as in gzip) Compress or decompress to
• -t –test
– Check integrity of the specified file(s), but
don't decompress them.
• This really performs a trial decompression and
throws away the result.
• -k –keep
– Keep (don't delete) input files during
compression or decompression.
• -s –small
– Reduce memory usage, for compression,
decompression and testing.
• -1 (or --fast) to -9 (or --best)
– Set the block size to 100 k, 200 k .. 900 k
– Has no effect when decompressing.
• decompresses files to stdout
• Cannot use bunzip2 to uncompress files
compressed with gzip and vice versa
• bzip2 -d
– decompresses all specified files.
– Files which were not created by bzip2 will be
detected and ignored
• warning issued.
• If the file does not end in one of the recognised endings:
• bzip2 uses the original name with.out appended.
• tar is a general-purpose archiving utility
– Stands for Tape Archive
– capable of packing many files into a single
– while retaining information needed to restore
the files fully, such as file permissions and
– Create a new archive
– Extract files from an archive
– List table of contents to an archive
– Update files
– Compare files in the archive to those in the
– print verbose information
– To keep any existing files when extracting
• f filename
– To specify that the tar file to be read or written is
• Parameter for gzip and bzip2:Parameter for gzip and bzip2:
– To specify that the data to be written to the tar file should
be compressed or that the data in the tar file is compressed
– Like z, but uses bzip2 instead of gzip;
• works only with newer versions of tar.
– f must be the last letter in the list of options.
• tar saves the pathname of each file
relative to the location where the tar file
was originally created.
– tar cvf bin.tar /bin
the directory bin is created in the working
directory of tar
– You can override this behavior using the P option when packing
tar files (not recommended to do!)