UNIX for Dummies Questions & Answers

i like to use

gunzip < filename | tar xvf -

I use basically the same method, but there's no need for the redirection....

gunzip filename | tar xvf -

does the same thing. I like to save keystrokes!

And as thumsup9 hints, using GNU tar, you can save even more keystrokes by using the builtin gzip decompression

tar xvzf foo.tar.gz

Cheers
ZB

I'm actually not even sure why i use redirect? i saw in an example years ago and have been using it ever since.
If I can save keystroke I certainly will.
i think i will adopt tar xvzf as my new, preferred method

That z flag on tar is not universal. As for using redirect, that's why I do and I'm not gonna switch. See this thread for part of the reason. The other part is that keystrokes are a cheap resource even for a slow typist like me. I often use superfluous parentheses in complex expressions. And in a script, I prefer
variable="string"
over
variable=string

In the same way, "gunzip < file | program" seems more clear than "gunzip file | program" especially if the reader never heard of gunzip. Of course, on the other hand, "gunzip < file" isn't going to fly. Here gunzip needs the old filename to construct the new filename. So rather than blindly adopting one technique or the other, be aware of the issues and make your own choice. There's not really a right or wrong here.

I actually had the occasion to test these tonight.

tar didn't support the z switch
tar xvzf filename.tar.gz
tar: z: unknown option
Usage: tar {txruc}[vfbFXhiBEelmopwnq[0-7]] [-k size] [tapefile] [blocksize] [exclude-file] [-I include-file] files ...

gunzip without the redirection operator only unzip's the file, pipe to tar didn't seem to work
gunzip filename.tar.gz | tar xvf -
tar: blocksize = 0


Therefore, i stand with my original command line of:
gunzip < filename.tar.gz | tar xvf -

Since it is the only command line that did what I needed.

The "z" switch to tar is supported in (primarily) GNU tar. You can get the gnu utilities from www.gnu.org and compile them for your system - in my opinion they are superior to a lot of the standard utilities supplied with most UNIX flavours, but of course this is just a personal preference.

Something else to throw into the melting pot is (under Linux)

zcat foo.tar.gz | tar xvf -

Some systems use "gzcat" instead.

Under certain circumstances (particularly within scripts) my rule of "saving keystrokes" doesn't apply. I'll always use ${varname} over $varname, string="value" over string=value, etc.... Whatever float's your boat I guess

Cheers
ZB

zazzybob,

zcat is compatible with compress/uncompress and gzcat with gzip/gunzip.