Strange behavior encountered while using tar

Question

I had a folder of useless C programs for a project. When I was compressing it using tar, I kept using

tar -cvf c-project

and then realized I'm setting the flag for the file name and I'm giving none.

So I tried remove the flag f and set the command to tar -cv c-project assuming, the name of the tar file would become c-project.tgz.

However, this is what happened.

This behavior doesn't appear when gzip is used. That is the additonal z flag is added.

Any idea why this is happening? The contents seem to be the content of the C files. However, why are they "scrambled"?

Answer 1

If you don't specify an output file, then tar outputs to "standard out" by default, which is typically your screen. Since the contents of a tar file isn't directly human-readable, this will appear to be garbage on your screen. The "standard out" behavior is useful when you pipe tar's output to another program, like tar -cv foodir | gzip > foodir.tgz. A shorter way to accomplish the same is tar -czvf foodir.tgz foodir. tar is an old program, and its syntax is quirky for historical reasons, so you'll probably find that there are just patterns for doing common tasks that you just get used to.

Answer 2

If you look with more attention you may notice that you wrote

tar -cvf c-project

It's equivalent to

tar -cvf c -p roject

O-O-O-ps... Indeed you try to create tar archive with name c and additional option p. Such option exist. So you don't get error p - unknown option. But you try to archive dir roject. This absent object. Unfortunately I can't see you screen short. You must just enquote "c-project". And the is no problem...