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4.5.3 Putting them together

Therefore, to archive a group of files and compress the result, you can use the commands:

# tar cvf backup.tar /etc
# gzip -9 backup.tar

The result will be backup.tar.gz. To unpack this file, use the reverse set of commands:

# gunzip backup.tar.gz
# tar xvf backup.tar

Of course always make sure that you are in the correct directory before unpacking a tar file.

You can use some UNIX cleverness to do all of this on one command line, as in the following:

# tar cvf - /etc gzip -9c > backup.tar.gz

Here, we are sending the tar file to ``-'', which stands for tar's standard output. This is piped to gzip, which compresses the incoming tar file, and the result is saved in backup.tar.gz. The -c option to gzip tells gzip to send its output to stdout, which is redirected to backup.tar.gz.

A single command used to unpack this archive would be:

# gunzip -c backup.tar.gz tar xvf -

Again, gunzip uncompresses the contents of backup.tar.gz and sends the resulting tar file to stdout. This is piped to tar, which reads ``-'', this time referring to tar's standard input.

Happily, the tar command also includes the z option to automatically compress/uncompress files on the fly, using the gzip compression algorithm.

For example, the command

# tar cvfz backup.tar.gz /etc

is equivalent to

# tar cvf backup.tar /etc
# gzip backup.tar

Just as the command

# tar xvfz backup.tar.Z

may be used instead of

# uncompress backup.tar.Z
# tar xvf backup.tar

Refer to the man pages for tar and gzip for more information.

       



next up previous contents index
Next: 4.6 Using Floppies and Up: 4.5 Archiving and Compressing Previous: 4.5.2 gzip and compress



Matt Welsh
mdw@sunsite.unc.edu