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diff --git a/chapter_04.xml b/chapter_04.xml index 0057cb2..0e37ca8 100644 --- a/chapter_04.xml +++ b/chapter_04.xml @@ -97,6 +97,14 @@ printf (3) - formatted output conversion <entry>8</entry> <entry align="right">System Administration</entry> </row> + <row> + <entry>9</entry> + <entry>Kernel API Descriptions</entry> + </row> + <row> + <entry>n</entry> + <entry>"New" - typically used to Tcl/Tk</entry> + </row> </tbody> </tgroup> </table> @@ -306,6 +314,124 @@ bar_2/ </section> <section> +<title>Archive and Compression</title> + +<para> +Everyone needs to package a lot of small files together for easy +storage from time to time, or perhaps you need to compress very large +files into a more manageable size? Maybe you want to do both of those +together? Thankfully there are several tools to do just that. +</para> + +<section> +<title>zip and unzip</title> + +<para> +You're probably familiar with .zip files. These are compressed files +that contain other files and directories. While we don't normally use +these files in the Linux world, they are still commonly used by other +operating systems, so we occasionally have to deal with them. +</para> + +<para> +In order to create a zip file, you'll (naturally) use the +<application>zip</application>(1) command. You can compress either +files or directories (or both) with <application>zip</application>, but +you'll have to use the <arg>-r</arg> argument for recursive action in +order to deal with directories. +</para> + +<screen><prompt>darkstar:~$ </prompt><userinput>zip -r /tmp/home.zip /home</userinput> +<prompt>darkstar:~$ </prompt><userinput>zip /tmp/large_file.zip +/tmp/large_file</userinput></screen> + +<para> +The order of the arguments is very important. The first filename must +be the zip file to create (if the .zip extension is ommitted, +<application>zip</application> will add it for you) and the rest are +files or directories to be added to the zip file. +</para> + +<para> +Naturally, <application>unzip</application>(1) will decompress a zip +archive file. +</para> + +<screen><prompt>darkstar:~$ </prompt><userinput>unzip /tmp/home.zip</userinput></screen> + +</section> + +<section> +<title>gzip</title> + +<para> +One of the oldest compression tools included in Slackware is +<application>gzip</application>(1), a compression tool that is only +capable or operating on a single file at a time. Whereas +<application>zip</application> is both a compression and an archival +tool, <application>gzip</application> is only capable of compression. +At first glance this seems like a draw-back, but it is really a +strength. The UNIX philosophy of making small tools that do their small +jobs well allows them to be combined in myriad ways. In order to +compress a file (or multiple files), simply pass them as arguments to +<application>gzip</application>. Whenever +<application>gzip</application> compresses a file, it adds a .gz +extension and removes the original file. +</para> + +<screen><prompt>darkstar:~$ </prompt><userinput>gzip /tmp/large_file</userinput></screen> + +<para> +Decompressing is just as straight-forward with +<application>gunzip</application> which will create a new uncompressed +file and delete the old one. +</para> + +<screen><prompt>darkstar:~$ </prompt><userinput>gunzip /tmp/large_file.gz</userinput> +<prompt>darkstar:~$ </prompt><userinput>ls /tmp/large_file*</userinput> +/tmp/large_file</screen> + +<para> +But suppose we don't want to delete the old compressed file, we just +want to read its contents or send them as input to another program? +The <application>zcat</application> program will read the gzip file, +decompress it in memory, and send the contents to the standard output +(the terminal screen unless it is redirected, see the next chapter for +more details on output redirection). +</para> + +<screen><prompt>darkstar:~$ </prompt><userinput>zcat /tmp/large_file.gz</userinput> +Wed Aug 26 10:00:38 CDT 2009 +Slackware 13.0 x86 is released as stable! Thanks to everyone who helped +make this release possible -- see the RELEASE_NOTES for the credits. +The ISOs are off to the replicator. This time it will be a 6 CD-ROM +32-bit set and a dual-sided 32-bit/64-bit x86/x86_64 DVD. We're taking +pre-orders now at store.slackware.com. Please consider picking up a copy +to help support the project. Once again, thanks to the entire Slackware +community for all the help testing and fixing things and offering +suggestions during this development cycle. +</screen> + +</section> + +<section> +<title>bzip2</title> + +<para> +One alternative to <application>gzip</application> is the +<application>bzip2</application>(1) compression utility which works in +almost the exact same way. The advantage to +<application>bzip2</application> is that it boasts greater compression +strength. Unfortunately, achieving that greater compression is a slow +process, so <application>bzip2</application> takes longer to run than +other alternatives. +</para> + +</section> + +</section> + +<section> <title>Reading Documents</title> <para> |