Notes

[tar] Compressed Archives

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tar creates a compressed archive. the file extension of the resulting archive is .tar and the tar archives are called tarballs..

GNU ‘tar’ saves many files together into a single tape or disk archive, and can restore individual files from the archive.

A .tar file is an archive, but it’s not compressed. .tar.gz is a an archive that is compressed.

Flags

  • c is for create, –create a new archive
  • v is for –verbose, verbosely list files processed, list out files as they are added to the archive
  • f is for –file=ARCHIVE, use archive file or device ARCHIVE, basically, specify the tar file that you wanna create. Since f lets you take an input it should always be the last flag..

tar can also work off of STDIN and STDOUT, f lets you specify if you wanna work with an existing tar file or if you wanna create one.

  • z is for compression, –compress (gzip) and –uncompress (gunzip)
  • x is for –extract
  • t is for –list, list the contents of an archive
  • r is for –append, add more files to an existing archive
  • u is for –update
  • -p restore permissions (can only be ysed with x)
  • -P preserve pathnames
  • -k Keep (don’t overwrite) existing files

Example tar commands:

compress a dir:

1tar -cvf archive.tar dir-to-archive

compress multiple files

1tar -cvf archive.tar file1 file2 file3

compress multiple files and dirs

1tar -cvf archive.tar dir1 dir2 file2 file3

Compresses tar archives

You can compress on the fly with the z flag

1tar -czvf archive.tar.gz dir-to-archive

You can also use gzip on a tarball to compress it.

1gzip archive.tar

Extract tarballs

Use the x flag instead of c

Extract all files from archive.tar.

1tar -xf archive.tar

Extract a compressed tarball

1tar -xzvf archive.tar.gz

Extract tarballs while restoring permissions

Use the -p flag. It’s to

Restore permissions (including ACLs, owner, file flags)

List the contents of a tarball without extracting it

Use the t or --list flag

1tar -tzvf archive.tar.gz

Handy when you wanna know what’s in a tarball, or to see if it’ll extract in the current dir or in it’s own subdir. Sometimes, you get a tar bomb when a tarball starts extracting all the files in your current dir instead of making its own folder.. Potentially clobbering files in your current dir, like README or something, that you might already have in the folder you are working in.

Getting a single file out of a tarball

Add more files to a previously created archive

Use the r flag

Update the archive with new files

Use the u flag. It updates the archive with new files, it also updates the existing files to their newer versions.

only append files newer than copy in archive

Read compressed files

cat in a compressed file is zcat. Use zcat to read files in an archive..

Notes:

  • f should be the last flag because it takes an option
  • it makes more sense to start flags with c, x and t so it’s clear right away if you are creating, extracting or listing..
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