Example uses of the Linux command "tar"

Introduction

In essence, a tar file is a method of creating an archive file which contains many other files.

Imagine you have a folder structure with files in it that you want to copy from one computer to another. You could write a script which performs the copy and places all the files in the correct folders on the destination machine.

It would be far easier if you could create a single file with all the files and folders incorporated as part of the file which you could then copy to the destination and extract.

Users who are used to using Windows software such as WinZip will already be aware of this sort of functionality but the difference between a zip file and a tar file is that the tar file isn't compressed.

It is quite common for a tar file to be compressed as shown in the guide showing how to extract tar.gz files.

This article will show you how to use the tar command.

How To Create A Tar File

Imagine your pictures folder under your home folder has lots of different folders with many images in each folder.

You can create a tar file containing all of your images whilst maintaining the folder structure using the following command:

tar -cvf photos ~/photos

The switches are as follows:

◈ -c = create
◈ -v = verbose
◈ -f = files

How To List The Files In A Tar File

You can list the contents of a tar file by using the following command:

tar -tf tarfilename

This provides a list of the files and folders within a tar file. You should always do this before extracting a tar file from a strange source.

At the very least a tar file might extract files to folders you weren't expecting and corrupt parts of your system so knowing which files are going where is a good starting point.

At the worst bad people create something called a tar bomb which is designed to destroy your system.he

The previous command simply gives a list of the files and folders. If you would like a more verbose view showing file sizes use the following command:

tar -tvf tarfilename

The switches are as follows:

◈ -t = list contents of an archive
◈ -f = file
◈ -v = verbose

How To Extract From A Tar File

Now that you have listed the files in a tar file you might wish to extract the tar file.

To extract the contents of a tar file use the following command:

tar -xvf tarfile

The switches are as follows:

◈ -x = extract
◈ -v = verbose
◈ -f = file

How To Append Files To A Tar File

If you want to add files into an existing tar file run the following command:

tar -rvf tarfilename /path/to/files

The switches are as follows:

◈ -r = Append
◈ -v = Verbose
◈ -f = Files

How To Append Files Only If They Are Newer

The problem with the previous command is that if you added files that already exist in the tar file they would be overwritten.

If you want to only add files if they are newer than existing files use the following command:

tar -uvf tarfilename /path/to/files

How To Prevent Tar From Overwriting Files Whilst Extracting

If you are extracting a tar file you may not want to overwrite files if they already exist.

This command makes sure that existing files are left alone:

tar -xkvf tarfilename

Only Extract Files That Are Newer Than Existing Files

If you are extracting a tar file you might be happy for files to be overwritten but only if the file in the tar file is newer than the existing file.

The following command shows how to do this:

tar --keep-newer-files -xvf tarfilename

How To Remove Files After Adding Them To A Tar File

A tar file remains uncompressed so if you had a 400-gigabyte file to a tar file you will have a 400-gigabyte file in its original location and tar file with a 400-gigabyte file in it.

You may wish to remove the original file when it is added to a tar file.

The following command shows how to do this:

tar --remove-files -cvf tarfilename /path/to/files

Compress A Tar File When You Create It

To compress a tar file as soon as it is created use the following command:

tar -cvfz tarfilename /path/to/files

Summary

The tar command has dozens of switches and more information can be found by using the man tar command or by running tar --help.

This guide provides the basics that most people need to know for creating and extracting tar files.