linux : archiving & compression

Archiving is the process of combining multiple files and directories (same or different sizes) into one file. Compression is the process of reducing the size of a file or directory.

Common type of compression:

• Gzip : with extension .tar.gz. It has fastest compression time.
• Bzip : with extension .tar.bz2
• Xz : with extension .tar.xz. It has smallest size compression.

Common programs for archiving files:

• tar
• zip
• gzip
• bzip2
• xz

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We will talk about how we use tar command. It has a lot of option that we can use:

• -c or --create : create a new file archive
• -f or --file : filename

# create an archive from multiple files
tar -cf ARCHIVE.tar FILE1.txt FILE2.txt FILE3.txt

# create an archive from a directory
tar -cf ARCHIVE.tar DIRECTORY

# using long command
tar --create --file ARCHIVE.tar DIRECTORY

• -X or --exclude : exclude a file

# exclude a file when creating an archive
tar -cf ARCHIVE.tar DIRECTORY --exclude=FILE.txt

• -x or --extract : extract an archive

# extract an archive file
tar -xf ARCHIVE.tar

# using long command
tar --extract --file ARCHIVE.tar

• -z : zip or unzip using gzip

create a compressed archive

# create an archive with gzip compression
tar -czf ARCHIVE.tar.gz DIRECTORY

# using gzip
gzip ARCHIVE.tar.gz DIRECTORY

extract a compressed archive

# extract an archive with gzip compression
tar -xzf ARCHIVE.tar.gz

# using gunzip --decompress
gunzip -d ARCHIVE.tar.gz

• -j : zip or unzip using bzip2

create a compressed archive

# create an archive with bzip compression
tar -cjf ARCHIVE.tar.bz2 DIRECTORY

# using bzip2
bzip2 ARCHIVE.tar.bz2 DIRECTORY

extract a compressed archive

# extract an archive with bzip compression
tar -xjf ARCHIVE.tar.bz2

# using bunzip2 --decompress
bunzip2 -d ARCHIVE.tar.bz2

• -J : zip or unzip using xz

create a compressed archive

# create an archive with xz compression
tar -cJf ARCHIVE.tar.xz DIRECTORY

# using xz
xz ARCHIVE.tar.xz DIRECTORY

extract a compressed archive

# extract an archive with xz compression
tar -xJf ARCHIVE.tar.xz

# using unxz --decompress
unxz -d ARCHIVE.tar.xz

• zip and unzip

create a compressed archive

# create using zip
zip ARCHIVE.zip DIRECTORY

extract a compressed archive

# extract using unzip
unzip ARCHIVE.zip

• -t or --list : list the contents of an archive without extracting it

# display contents of an archive
tar -tf ARCHIVE.tar

# display contents using gzip
gzip -l ARCHIVE.tar.gz

# display contents using unzip
unzip -l ARCHIVE.zip

• -r or --append : append files to the end of an archive

# append files to an archive
tar -rf ARCHIVE.tar FILE.txt

# using --append
tar --append -file ARCHIVE.tar FILE.txt

• -u or --update : Append files which are newer than the corresponding copy in the archive

# append files to an archive
tar -uf ARCHIVE.tar FILE.txt

# using --append
tar --update -file ARCHIVE.tar FILE.txt

• delete : delete files inside an archive

# delete from the archive
tar --delete --file ARCHIVE.tar FILE.txt

• -C or --directory : change the directory

# change location of unarchived files
tar -xf ARCHIVE.tar -C DIRECTORY

• -v or --verbose : see the detailed output
  We can combine this options with all others

• --wildcards : matching on the filenames within an archive
  

# extract a particular type of file
tar -xf ARCHIVE.tar --wildcards "*.txt"