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Archival & Compression Commands

CS155 Archives

Archival and Compression: gzip, bzip2

• To save space we can compress files using two common compression tools.
• Gnu zip – a compression tool from GNU
  • gzip : compress file
  • gunzip : uncompress file
• Usually better compression, but slower:
  • bzip2 : compress file
  • bunzip2 : uncompress file

Compression Examples

% ls -l
total 112
-rw------- 1 boese fac 108447 Feb 6 10:39 test_file
% gzip test_file
% ls -l
total 32
-rw------- 1 boese fac 32174 Feb 6 10:39 test_file.gz
% gunzip test_file.gz
% bzip2 test_file
% ls -l
total 28
-rw------- 1 boese fac 27350 Feb 6 10:39 test_file.bz2

• bzip2 usually produces smaller files, but it also takes longer to run.

Archival and Compression: tar

• Store many files together as one file (packages files together as a single archival file)
• Compresses files
• Can maintain directory structure or not
• Methods
  • tar – tape archive
    • tar allows us to put many files into a single file while preserving the directory structure
  • zip - works on Unix and Windows
    • ditto
• Archiving files using tar or zip is a convenient way of backing up files or sending a group of files to someone.

Archival and Compression: tar

• tar – tape archive
• tar allows us to put many files into a single file while preserving the directory structure
• Archiving files using tar is a convenient way of backing up files or sending a group of files to someone.

tar: Usage

• Usage: tar operation [options] files
• Operations:
  • c – create an archive
  • x – extract files from archive
  • t – list files in archive
• Options:
  • v – verbose output
  • f – file name follows immediately as the next item
  • j – filter through bzip2
  • z – filter through gzip

tar: Examples

• Create a tar file from my_dir and my_file
  tar -cvf my_tar.tar my_dir/ my_file
• List the contents of the created tar file
  tar -tvf my_tar.tar
• Extract everything in the archive into the current directory
  tar -xvf my_tar.tar
• Extract just my_file2 into the current directory
  tar -xvf my_tar.tar my_file2

Archival with Compression

Using tar, we can filter archives through a compression program.

• Create a gzipped tar file of the directory my_files:
  tar -zcvf my_tar.tgz my_files/
• Extract from a gzipped tar file into the current directory:
  tar -zxvf my_tar.tgz
• Create a bzip2 tar file of the current directory:
  tar -cjvf /tmp/my_tar.tbz .

zip: Usage

• Usage: zip operation [options] files
• Options:
  • f - freshen: only changed files
  • r - recurse into directories
  • x - exclude the following names
  • u - update: only changed or new files
  • v - verbose: print info
  • D - do not add directory entries

zip: Examples

• Create a zip file from files in my_dir and my_file
  zip myArchive.zip my_dir/* my_file
• List the contents of the created zip file
  unzip -l myArchive.zip
• Extract the contents into the directory temp_dir
  unzip -d temp_dir myArchive.zip
• Append the file my_file2 to the archive
  zip -u myArchive.zip my_file2
• Extract my_file2 into temp_dir
  unzip -d temp_dir myArchive.zip my_file2