📄 0072-0074.html

📁 linux-unix130.linux.and.unix.ebooks130 linux and unix ebookslinuxLearning Linux - Collection of 12 E
💻 HTML
字号:




<HTML>

<HEAD>

<TITLE>Maximum RPM (RPM):Getting Information About Packages:EarthWeb Inc.-</TITLE>

<META NAME="ROBOTS" CONTENT="NOINDEX, NOFOLLOW">
<SCRIPT>
<!--
function displayWindow(url, width, height) {
        var Win = window.open(url,"displayWindow",'width=' + width +
',height=' + height + ',resizable=1,scrollbars=yes');
}
//-->
</SCRIPT>
</HEAD>

 -->




<!-- ISBN=0672311054 //-->

<!-- TITLE=Maximum RPM (RPM)//-->

<!-- AUTHOR=Edward Bailey//-->

<!-- PUBLISHER=Macmillan Computer Publishing//-->

<!-- IMPRINT=Sams//-->

<!-- CHAPTER=05 //-->

<!-- PAGES=0053-0078 //-->

<!-- UNASSIGNED1 //-->

<!-- UNASSIGNED2 //-->









<P><CENTER>

<a href="0069-0071.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="0075-0078.html">Next</A>

</CENTER></P>



<A NAME="PAGENUM-72"><P>Page 72</P></A>







<P>Let's put together a format string that will display the package name, followed by the name

of every file that package contains. We'll try it on the

adduser package first since it contains only one file:

</P>

<!-- CODE SNIP //-->

<PRE>

# rpm -q --queryformat `%{NAME}: %{FILENAMES}\n' adduser

adduser: /usr/sbin/adduser

#

</PRE>

<!-- END CODE SNIP //-->



<P>Hey, not bad: Got it on the first try. Now let's try it on a package with more than one file:

</P>

<!-- CODE SNIP //-->

<PRE>

# rpm -q --queryformat `%{NAME}: %{FILENAMES}\n' etcskel

etcskel: (array)

#

</PRE>

<!-- END CODE SNIP //-->



<P>Hmmm. What went wrong? It worked before. Well, it worked before because the

adduser package contained only one file. The

FILENAMES tag points to an array of names, so when

there is more than one file in a package, there's a problem.

</P>



<P>But there is a solution. It's called an

iterator. An iterator can step through each entry in

an array, producing output as it goes. Iterators are created when square braces enclose one or

more tags and literal text. Since we want to iterate through the

FILENAMES array, let's enclose that tag in the iterator:

</P>

<!-- CODE SNIP //-->

<PRE>

# rpm -q --queryformat `%{NAME}: [%{FILENAMES}]\n' etcskel

etcskel: /etc/skel/etc/skel/.Xclients/etc/skel/.Xdefaults/etc/skel/.ba

#

</PRE>

<!-- END CODE SNIP //-->



<P>There was more output: It went right off the screen in one long line. The problem? We

didn't include a newline escape sequence inside the iterator. Let's try it again:

</P>

<!-- CODE //-->

<PRE>

# rpm -q --queryformat `%{NAME}: [%{FILENAMES}\n]' etcskel

etcskel: /etc/skel

/etc/skel/.Xclients

/etc/skel/.Xdefaults

/etc/skel/.bash logout

/etc/skel/.bash profile

/etc/skel/.bashrc

/etc/skel/.xsession

#

</PRE>

<!-- END CODE //-->



<P>That's more like it. If we wanted, we could put another file-related tag inside the iterator. If

we included the FILESIZES tag, we'd be able to see the name of each file, as well as how big it was:

</P>

<!-- CODE //-->

<PRE>

# rpm -q --queryformat `%{NAME}: [%{FILENAMES} (%{FILESIZES} bytes) \n]'\

&gt; etcskel

etcskel: /etc/skel (1024 bytes)

/etc/skel/.Xclients (551 bytes)

/etc/skel/.Xdefaults (3785 bytes)

/etc/skel/.bash logout (24 bytes)

/etc/skel/.bash profile (220 bytes)

/etc/skel/.bashrc (124 bytes)

/etc/skel/.xsession (9 bytes)

#

</PRE>

<!-- END CODE //-->



<P>That's pretty nice. But it would be even nicer if the package name appeared on each line,

along with the filename and size. Maybe if we put the

NAME tag inside the iterator:

</P>



<A NAME="PAGENUM-73"><P>Page 73</P></A>





<!-- CODE SNIP //-->

<PRE>

# rpm -q --queryformat `[%{NAME}: %{FILENAMES} (%{FILESIZES} bytes) \n]'\

&gt; etcskel

etcskel: /etc/skel(parallel array size mismatch)#

</PRE>

<!-- END CODE SNIP //-->



<P>The error message says it all. The FILENAMES and

FILESIZES arrays are the same size. The NAME tag isn't

even an array. Of course the sizes don't match!

</P>



<B>5.2.2.11.7. Iterating Single-Entry Tags

</B>



<P>If a tag has only one piece of data, it's possible to put it in an iterator and have its one piece

of data displayed with every iteration. This is done by preceding the tag name with an equal

sign. Let's try it on our current example:

</P>

<!-- CODE //-->

<PRE>

# rpm -q --queryformat `[%{=NAME}: %{FILENAMES} (%{FILESIZES} bytes) \n]'\

&gt; etcskel

etcskel: /etc/skel (1024 bytes)

etcskel: /etc/skel/.Xclients (551 bytes)

etcskel: /etc/skel/.Xdefaults (3785 bytes)

etcskel: /etc/skel/.bash logout (24 bytes)

etcskel: /etc/skel/.bash profile (220 bytes)

etcskel: /etc/skel/.bashrc (124 bytes)

etcskel: /etc/skel/.xsession (9 bytes)

#

</PRE>

<!-- END CODE //-->



<P>That's about all there is to format strings. Now, if RPM's standard output doesn't give

you what you want, you have no reason to complain. Just

--queryformat it!

</P>



<B>5.2.2.11.8. In Case You Were Wondering&#133;

</B>



<P>What's that? You say you don't know what tags are available? You can use RPM's

--querytags option. When used as the only option (that is,

rpm --querytags), it produces a list of available tags. It should be noted that RPM displays the complete tag name. For instance,

RPMTAG_ARCH is the complete name, yet you'll only need to use

ARCH in your format string. Here's a partial example of the

--querytags option in action:

</P>

<!-- CODE //-->

<PRE>

# rpm --querytags

RPMTAG_NAME

RPMTAG_VERSION

RPMTAG_RELEASE

...

 RPMTAG_VERIFYSCRIPT

#

</PRE>

<!-- END CODE //-->



<P>Be forewarned: The full list is quite lengthy. At the time this book was written, there were

more than 60 tags! You'll notice that each tag is printed in uppercase and is

preceded with RPMTAG_. If we were to use that last tag,

RPMTAG_VERIFYSCRIPT, in a format string, it could be specified

in any of the following ways:

</P>

<!-- CODE SNIP //-->

<PRE>

%{RPMTAG_VERIFYSCRIPT}



%{RPMTAG_VerifyScript}

</PRE>

<!-- END CODE SNIP //-->



<A NAME="PAGENUM-74"><P>Page 74</P></A>



<!-- CODE //-->

<PRE>



%{RPMTAG_VeRiFyScRiPt}



%{VERIFYSCRIPT}



%{VerifyScript}



%{VeRiFyScRiPt}

</PRE>

<!-- END CODE //-->



<P>The only hard-and-fast rule regarding tags is that if you include the

RPMTAG_ prefix, it must be all uppercase. The fourth example here shows the traditional way of specifying a tag:

prefix omitted, all uppercase. The choice, however, is yours.

</P>



<P>One other thing to keep in mind is that not every package will have every type of tagged

information available. In cases where the requested information is not available, RPM will

display (none) or (unknown). There are also a few tags that, for one reason or another, will not

produce useful output when they are used in a format string. For a comprehensive list of

queryformat tags, see Appendix D, &quot;Available Tags for

--queryformat.&quot;

</P>



<H4>

5.2.3. Getting a Lot More Information with -vv

</H4>



<P>Sometimes it's necessary to have even more information than we can get with

-v. By adding another v, we can start to see more of RPM's inner workings:

</P>

<!-- CODE //-->

<PRE>

# rpm -qvv rpm

D: opening database in //var/lib/rpm/

D: querying record number 2341208

rpm-2.3-1

#

</PRE>

<!-- END CODE //-->



<P>The lines starting with D: have been added by using

-vv. We can see where the RPM database is located and what record number contains information on the

rpm-2.3-1 package. Following that is the usual output.

</P>



<P>In the vast majority of cases, it will not be necessary to use

-vv. It is normally used by software engineers working on RPM itself, and the output can change without notice. However, it's

a handy way to gain insight into RPM's inner workings.

</P>



<H4><A NAME="ch05_ 6">

5.2.4. --root &lt;path&gt;: Use &lt;path&gt; As an Alternate Root

</A></H4>



<P>Adding --root &lt;path&gt; to a query command

forces RPM to assume that the directory specified by

&lt;path&gt; is actually the root directory. In addition, RPM expects its database to reside in

the directory specified by the dbpath rpmrc file entry, relative to

&lt;path&gt;.

</P>



<P>Normally, this option is only used during an initial system install or when a system has

been booted off a rescue disk and some packages need to be re-installed in order to restore

normal operation.

</P>



<P><CENTER>

<a href="0069-0071.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="0075-0078.html">Next</A>

</CENTER></P>











</td>
</tr>
</table>

<!-- begin footer information -->







</body></html>
⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -