unizp command

I have a file (nas-1.4.src.tar.gz) to unzip on Unix and instructions say to do this:
You should have recieved the following file:
(where x.y is the current revision)
nas-x.y.src.tar.gz - gziped tar archive of the source distribution.
Unzip/untar this use 'gzcat nas-x.y.src.tar.gz |tar -xvf -'.

And I have not unzipped anything on unix before, so I get usage warnings when I execute: gzcat nas-1.4.src.tar.gz |tar -xvf -

P.S. I know this belongs to UNIX forum.

tar -xvzf nas-1.4.src.tar.gz

Then why is there a "|" in the original instructions? And what is all that there in original command anyway?
Thanks for the suggestion.
here is what I get now:
% tar -xvzf nas-1.4.src.tar.gz
tar: z: unknown function modifier
Usage: tar {c|r|t|u|x}[BDeEFhilmnopPqvw[0-7]][bfk][X...] [blocksize] [tarfile] [size] [exclude-file...] {file | -I include-file | -C directory file}...

Ummm... you posted 2 questions in the Unix forum, one of which was answered. The other question was really obscure and no one knew what the answer was (IIRC, no one answered you correctly when you posted the same question in the lounge later). Instead of polluting the lounge, you should keep posting your UNIX questions in the *nix forum.

To Scorpions4ever: Somehow actually lounge-people actually helped me figure out my last Unix question, so I found it more helpful, but you are right.
Forget it, I will get myself out of here.
<edit>
if I knew how to move my thread
</edit>

Thread moved.

The idea of specific forums is to post questions in them. Don't just ignore them becaues the lounge gives you better response times.

To start w/ the first part of your question, the | is a pipe and what they are telling you to do is run the unzip program on your box, take the result for the unzip and "pipe" it to the tar command. Just one way of running two commands in order from one command prompt.

As for adding the z command to the tar funciton, this will work on some systems, mostly linux systems out of the box, but will also work on a unix system if your environment supports it. Seems like yours is not configured for it. So, to get the job done, try one of the following:

First, check to ensure the file is really a gzip file by executing:

file *

This will return the type of file and if it is of type gzip you can continue w/:

gunzip filename.tar.gz

then:

tar -xvf filename.tar

or, if you want to get fancy, you can do it all in one shot by:

gunzip filename.tar.gz;tar -xvf filename.tar

Hope this helps to clear things up.

Thank you for the detailed explanation. At least now I understand.
Apologize for my prejudice to this forum...