Sunday, August 16, 2009

Partially extracting a tarball

I've never had to extract just a small part of a tarball before so it took a little bit of digging to determine how to do that. It's simple with other archivers e.g. zip, rar et al but tar requires just a couple of extra options to make it happen.

Let's say you have a gzipped tarball that contains all your logs from /var/log with fully qualified paths. One thing to remember is that tar will always remove any leading / from all paths it processes. This means if you ran the tar command as follows:

tar zcf /tmp/logs.tar.gz /var/log

you will have a gzipped tarball containing files such as:


With this in mind, if you want to extract just your web server log files located in var/log/httpd, you can use the following commandline:

tar zxf /tmp/logs.tar.gz --wildcards 'var/log/httpd/*'

The quotes are necessary so the wildcard doesn't get extrapolated. That command will result in the var/log/httpd directory structure being created in your current dir and you will find that directory populated with the access.log and error.log files.

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