How to Save the World with tar

While there are hundreds of difficult-to-understand commands out there, few have acquired the notoriety of tar. Most guides are filled with abstruse commands such as tar -czvf archive.tar.gz ~/Downloads/ with little to no explanation. Based on conversations I've had, people who interact with tar tend to just memorize a basic command or two, like tar -xvf <filename> and hope for the best.

Let's take a closer look at tar and learn how it actually works.

A Quick Summary

tar is used for creating and interacting with archive files; .tar archive are similar in functionality to .zip files, which you may be more familiar with.

The name "tar" is short for "tape archives"; the original idea behind tar is that the archives in question would be stored on tape. In contemporary usage, that's not usually the case.

The "Easy" Way to Learn

The best explanation of tar is in its manual page.

$ man tar

However, this man page is extremely long and most people skip it altogether. Still, if you want a deeper understanding than what this guide will give you, the man page is the place to go.

Usage Styles

"Traditional" Usage

$ tar xvf archive.tar.gz

I won't cover this style in this article. Most of the basics are similar to Unix-style flags, and any other information you need to know is explained within man tar under Description ⇒ Option Styles. It's not the style I recommend you use, but it may be handy to understand if you see it in another guide.

"Unix-style" Usage

$ tar -xvf archive.tar.gz

These are standard short flags; you can use them individually (-x -v -f) or combine them (-xvf). This is the form you'll usually see used.

"GNU-style" Usage

$ tar --extract --verbose --file=archive.tar.gz

I think this is the most straightforward way to use tar; it's much clearer what the different flags mean and which arguments are passed to which flags. However, it's much harder to type out, so it isn't usually used.

Something many people don't know, though, is that you don't have to type out the full flags; you can just use the first letters, as long as the letters you type are unique to one flag.

$ tar --ext --verbo --file=archive.tar.gz

If you shorten a flag too far and there are multiple possibilities, tar will warn you and give you the possible completions.

Flag Walkthrough

Let's go through some of the most useful flags one by one and learn how they're used.

--verbose/-v

The --verbose flag just makes sure that you'll see all output from the command you run; by default, most tar commands will just do everything without returning any output, making it hard to tell if anything is happening, especially when a command takes a long time to run.

As a general rule, I add --verbose to almost every tar command I run; I like seeing what's going on. It will, though, spit out a ton of information, filling up your terminal screen, which might not be what you want.

--extract/-x

This flag says to extract the contents of an archive; you'll need to use the --file flag for it to do anything, which we'll learn about next.

Optionally, it takes arguments to specify which files to extract.

--file/-f

This flag specifies the archive file that you'll be working with, whether you're creating it, reading from it, adding files, etc. It takes one argument, the location of the archive file.

This is a good time to talk about how to pass arguments in tar. The long flags are the easiest to pass to:

$ tar --extract --file=archive.tar.gz

You can use a space instead of the =, but I suggest you use = for clarity.

For short flags, the argument value must follow the flag it's being passed to. This can take multiple forms:

$ tar -f archive.tar.gz -xv

$ tar -xvf archive.tar.gz

--list/-t

This flag says to list everything in an archive specified by --file or -f.

$ tar --list --file=archive.tar.gz

$ tar -tf archive.tar.gz

I don't generally bother including -v with this, since it'll be outputting the contents of the archive anyway.

Optionally, this takes arguments to specify which files to list.

--create/-c

This flag says to create a new tar archive with the filename and location specified by -f or --file. It takes one or multiple arguments to specify which files to add to the new archive.

$ tar --create=~/school --file=school.tar --verbose

$ tar --create ~/school ~/Downloads ~/writing --file=archive.tar --verbose

$ tar -cvf archive.tar ~/projects

Note that arguments passed to the action flag (such as -c, -t, -x) can be put at the end of the command, after all the other flags, as shown in the last example above. I couldn't find any specific rationale for that in the tar manpage, but it works and people often do it that way.

--gzip/-z

--create alone doesn't apply any compression to files; to do that, you need to select a compression method. I personally always use gzip, which is applied with the --gzip or -z flag.

$ tar -czvf archive.tar.gz ~/Downloads

To use a different compression type, swap out this flag for the flag of the type you want to use. By convention, an extra file extension is appended to compressed archives, depending on the type of compression.

• --gzip/-z - gzip compression, uses .tar.gz
• --bzip2/-j - bzip2 compression, uses .tar.bz2
• --xz/-J - xz compression, uses .tar.xz

There are some others too, but you get the idea. See man tar for a full list of compression methods.

--append/-r

This will add files to an archive. Use it the same way you would --create/-c; use --file/-f to specify the archive, then pass directory and file paths to it to have them added to the archive.

$ tar -rvf school.tar.gz ~/Downloads/syllabus.pdf

More

There are many other flags for tar, some of which may be useful to you. The goal of this article was largely to get you to the point where reading the manual page will actually be helpful rather than just daunting. If you need to do something you don't know how to with tar, here's what I'd recommend:

1. Begin by searching up what you want to do and finding a guide for it. Unfortunately, most guides to tar aren't very conducive to actually understanding what you're doing, just rote memorization.
2. Take any flags you don't understand from what you find and look for them in man tar to get full instructions for how to use them. The manpage is actually pretty helpful if you're just looking up flags with a basic preexisting knowledge of how tar works.

Practice

Let's try this out; I'll begin by giving you some example commands with tar (using short flags, since the long ones are pretty easy). See if you can figure out what they do, then look at the explanation to test your knowledge.

$ tar -xvf archive.tar.gz

$ tar -xvwf archive.tar

$ tar -cavf backup.tar.gz ~/Documents

Conclusion

Congratulations, you know enough about tar to save the world from nuclear destruction! Go forth and use your newfound knowledge for good, not evil. (Or, you know, if you want to use it for evil, that's up to you, I suppose.)

See you next time; we'll be considering whether file managers are really necessary.