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<TITLE>Maximum RPM (RPM):Building Packages for Multiple Architectures and Operating Systems:EarthWeb Inc.-</TITLE>
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<!-- ISBN=0672311054 //-->
<!-- TITLE=Maximum RPM (RPM)//-->
<!-- AUTHOR=Edward Bailey//-->
<!-- PUBLISHER=Macmillan Computer Publishing//-->
<!-- IMPRINT=Sams//-->
<!-- CHAPTER=19 //-->
<!-- PAGES=0263-0274 //-->
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<a href="0267-0269.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="0273-0274.html">Next</A>
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<A NAME="PAGENUM-270"><P>Page 270</P></A>
<H4><A NAME="ch19_ 18">
19.5.1. The excludexxx Tags
</A></H4>
<P>excludexxx tags are used to direct RPM to ensure that the package does not attempt to
build on the excluded platforms. One or more platforms may be specified after the
excludexxx tags, separated by either spaces or commas. Here are two examples:
</P>
<!-- CODE SNIP //-->
<PRE>
ExcludeArch: sparc alpha
ExcludeOS: Irix
</PRE>
<!-- END CODE SNIP //-->
<P>The first line prevents systems based on the Sun SPARC and Digital Alpha/AXP
architectures from attempting to build the package. The second line ensures that the package will not
be built for the Silicon Graphics operating system Irix.
</P>
<P>If a build is attempted on an excluded architecture or operating system, the following
message will be displayed, and the build will fail:
</P>
<!-- CODE SNIP //-->
<PRE>
# rpm -ba cdplayer-1.0.spec
Arch mismatch!
cdplayer-1.0.spec doesn't build on this architecture
#
</PRE>
<!-- END CODE SNIP //-->
<P>excludexxx tags are meant to explicitly prevent a finite set of architectures or operating
systems from building a package. If your goal is to ensure that a package will build on only
one architecture, you should use the exclusivexxx tags.
</P>
<H4><A NAME="ch19_ 19">
19.5.2. The exclusivexxx Tags
</A></H4>
<P>exclusivexxx tags are used to direct RPM to only build the package on the specified
platforms. These tags ensure that in the future no brand-new platform will
mistakenly attempt to build the package. RPM will build the package on the specified platforms only.
</P>
<P>The syntax of the exclusivexxx tags is identical to that of
excludexxx:
</P>
<!-- CODE SNIP //-->
<PRE>
ExclusiveArch: sparc alpha
ExclusiveOS: Irix
</PRE>
<!-- END CODE SNIP //-->
<P>In the first line, the package will only build on a Sun SPARC or Digital Alpha/AXP system.
In the second, the package will only be built on the Irix operating system.
</P>
<P>exclusivexxx tags are meant to explicitly allow a finite set of architectures or operating
systems to build a package. If your goal is to ensure that a package will
not build on a specific platform, you should use the
excludexxx tag.
</P>
<H3><A NAME="ch19_ 20">
19.6. Platform-Dependent Conditionals
</A></H3>
<P>Of course, the control exerted by the
excludexxx and exclusivexxx tags over package
building is often too coarse. There may be packages, for example, that would build just fine on
another platform, if only you could substitute a platform-specific patch file or change some paths
in the %files list.
</P>
<A NAME="PAGENUM-271"><P>Page 271</P></A>
<P>The key to exerting this kind of platform-specific control in the spec file is to use RPM's
conditionals. The conditionals provide a general-purpose means of constructing a platform-<BR>
specific version of the spec file during the actual build process.
</P>
<H4><A NAME="ch19_ 21">
19.6.1. Common Features of All Conditionals
</A></H4>
<P>A few things are common to each conditional, so let's discuss them first. The first thing is
that conditionals are block structured. The second is that conditionals can be nested. Finally,
conditionals can span any part of the spec file.
</P>
<H4><A NAME="ch19_ 22">
19.6.1.1. Conditionals Are Block Structured
</A></H4>
<P>Every conditional is block structured—in other words, the conditional begins at a certain
point within the spec file and continues some number of lines until it is ended. This forms a
block that will be used or ignored, depending on the platform the conditional is checking for as
well as the build platform itself.
</P>
<P>Every conditional starts with a line beginning with
%if and is followed by one of four
platform-related conditions. Every conditional ends with a line containing
%endif.
</P>
<P>Ignoring the platform-related conditions for a moment, here's an example of a conditional
block:
</P>
<!-- CODE SNIP //-->
<PRE>
%ifos Linux
Summary: This is a package for the Linux operating system
%endif
</PRE>
<!-- END CODE SNIP //-->
<P>It's a one-line block, but a block nonetheless.
</P>
<P>There's also another style of conditional block. As before, it starts with
%if and ends with %endif. But there's something new in the middle:
</P>
<!-- CODE //-->
<PRE>
%ifos Linux
Summary: This is a package for the Linux operating system
%else
Summary: This is a package for some other operating system
%endif
</PRE>
<!-- END CODE //-->
<P>Here we've replaced one summary tag with another.
</P>
<H4><A NAME="ch19_ 23">
19.6.1.2. Conditionals Can Be Nested
</A></H4>
<P>Conditionals can be nested—that is, the block formed by
one conditional can enclose another conditional. Here's an example:
</P>
<!-- CODE //-->
<PRE>
%ifarch i386
echo "This is an i386"
%ifos Linux
echo "This is a Linux system"
</PRE>
<!-- END CODE //-->
<A NAME="PAGENUM-272"><P>Page 272</P></A>
<!-- CODE //-->
<PRE>
%else
echo "This is not a Linux system"
%endif
%else
echo "This is not an i386"
%endif
</PRE>
<!-- END CODE //-->
<P>In this example, the first conditional block formed by the
%ifarch i386 line contains a
complete %ifos...%else...%endif conditional. Therefore, if the build system were Intel
based, the %ifos conditional would be tested. If the build system were not Intel based, the
%ifos conditional would not be tested.
</P>
<H4><A NAME="ch19_ 24">
19.6.1.3. Conditionals Can Cross Spec File Sections
</A></H4>
<P>The next thing each conditional has in common is that there is no limit to the number of
lines a conditional block can contain. You could enclose the entire spec file within a
conditional. But it's much better to use conditionals to insert only the appropriate platform-specific
contents.
</P>
<P>
Now that we have the basics out of the way, let's take a look at each of the conditionals and
see how they work.
</P>
<H4><A NAME="ch19_ 25">
19.6.2. %ifxxx
</A></H4>
<P>The %ifxxx conditionals are used to control the inclusion of a block as long as the
platform-dependent information is true. Here is an example:
</P>
<!-- CODE SNIP //-->
<PRE>
%ifarch i386 alpha
</PRE>
<!-- END CODE SNIP //-->
<P>In this case, the block following the conditional would be included only if the build
architecture were i386 or alpha.
</P>
<P>Here's another example:
</P>
<!-- CODE SNIP //-->
<PRE>
%ifos Linux
</PRE>
<!-- END CODE SNIP //-->
<P>This example would include the block following the conditional only if the operating
system were Linux.
</P>
<H4><A NAME="ch19_ 26">
19.6.3. %ifnxxx
</A></H4>
<P>The %ifnxxx conditionals are used to control the inclusion of a block as long as the
platform-dependent information is not true. Here is an example:
</P>
<!-- CODE SNIP //-->
<PRE>
%ifnarch i386 alpha
</PRE>
<!-- END CODE SNIP //-->
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