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<html>
<head>
</head>
<body>
<div class="h2 app" style="border-left: 0px" id="customcontent">
<h2>What is SCons?</h2>
<p>SCons is a next-generation,
cross-platform, build tool.
Think of SCons as an improved
substitute for the classic
<tt>Make</tt> utility
with integrated functionality
similar to <tt>autoconf</tt>/<tt>automake</tt>
and compiler caches such as <tt>ccache</tt>.
</p>
<p>
Unlike build tools that invent their own mini-language
or wedge a scripting language onto some other
configuration file syntax,
SCons configuration files
are actually Python scripts.
The ability to script your build
gives you a tremendous amount of flexibility
to solve complicated build problems
in surprisingly small amounts of maintainable code.
</p>
<p>
In short, SCons is an easier, more reliable
and more flexible way to build software.
</p>
<!--
<h2><b>Goal</b></h2>
<p>The primary goal of The SCons Project
is to become the premiere enterprise-quality tool for
building cross-platform, multi-language software projects
by offering unparalleled <b>reliability</b> and <b>flexibility</b>
to software buildmasters and developers.
</p>
<p>
Yeah, yeah, every project has similar lofty mom-and-apple-pie goals,
blah, blah, blah...
So why is SCons any different?
Fair question.
If you go to our public home page at
<a href="http://www.scons.org/">http://www.scons.org</a>
you'll get the usual lists of
supported features and platforms, testimonials, etc.
But you're presumably at <emphasis>this</emphasis>
project page because you're interested in digging a little deeper.
So here are the <emphasis>philosophical viewpoints</emphasis>
that we think contribute to SCons being
a really distinctive software build tool:
</p>
<ul>
<li>
<strong>Software builds are getting more complicated, not less</strong>
<p>
The proliferation of programming languages and technologies
have led to increasingly difficult demands being
placed on traditional software build tools Make.
EVen if you stick to one language--a well-worn
and mature one like C, for example--the
differences between the various C tool chains
and how they behave on various platforms
make it a real challenge
to keep your software builds simple and reliable.
</p>
<p>
Consequently, SCons is a build tool
</p>
</li>
<li>
<strong>Effective software building is not a language design issue</strong>
<p>
There are a lot of build tools out there,
and it seems like a new one pops up every week
as someone gets the urge to fix some particularly
bad build problem that they're facing.
Most build tools have, historically,
invented some special configuration file format
to express dependencies and actions.
The problem is that by the time you take care of all
of the different ways people
you really want to have the flexibility
that a scripting language gives:
loops, conditionals, real data structures, etc.
(It's interesting to note that the Ant community is
working hard on adding more scriptability to their
XML-based Ant files,
and James Duncan Davidson, Ant's creator,
is on record as saying that he'd use a scripting
language if he were doing it over again.)
</p>
<p>
</p>
<p>
Note that SCons is not completely pure in this regard.
</p>
</li>
<li>
<strong>You want to encapsulate software build complexity
so most developers don't even have to think about it</strong>
<pp>
XXX
</pp>
</li>
<li>
<strong>Overall, a reliable build that takes a little longer is
cheaper than a fast build that you can't rely on</strong>
<p>
This one is sometimes tough to swallow,
because we all want the build to be as quick as possible
when we're in that tight edit-build-debug development cycle.
The problem is that if you take shortcuts in how your
build tool manages the dependencies,
you waste time chasing phantom problems
that simply go away because you finally give up
and do a <tt>make clean; make</tt>.
</p>
</li>
<li>
<strong>Building software in multiple side-by-side variants is crucial
in a multi-platform world</strong>
<pp>
XXX
</pp>
</li>
</ul>
-->
<h2><b>SCons Features</b></h2>
<ul>
<li>
<strong>Configuration files are Python scripts</strong>
<p>
This provides much more flexibility for solving
difficult build problems
than traditional build tools.
</p>
</li>
<li>
<strong>Reliable, automatic dependency analysis</strong>
<p>
C, C++ and Fortran are scanned for dependencies,
eliminating the need for a separate <tt>make depend</tt> step
or a <tt>make clean</tt> to get all of the dependencies.
Avoids the time waste from debugging phantom problems
that mysteriously disappear after you
<tt>make clean; make</tt>.
Easily extended to scan for other languages or file types.
</p>
</li>
<li>
<strong>Built-in support for multiple languages</strong>
<p>
C, C++, D, Java, Fortran, Yacc, Lex, Qt and SWIG.
Can also build TeX and LaTeX documents.
Easily extended for other languages or file types.
</p>
</li>
<li>
<strong>Cross-platform</strong>
<p>
Known to work on Linux,
other POSIX systems (AIX, *BSD, HP/UX, IRIX, Solaris),
Windows (NT, 2000, XP),
Mac OS X,
and OS/2.
</p>
</li>
<li>
<strong>Fetch files from SCM systems or central directory trees</strong>
<p>
Built-in support for SCCS, RCS, CVS, BitKeeper and Perforce.
On-disk directory trees can be searched for source files
or pre-built target files.
</p>
</li>
<li>
<strong>Support for Microsoft Visual Studio .NET and 2005</strong>
<p>
Generates <tt>.dsp</tt> and <tt>.dsw</tt> files,
or <tt>.sln</tt> and <tt>.vcproj</tt> files,
from the same build configuration used to build on all platforms.
Allows Windows developers to do all the productive
point-and-click debugging they're used to
without having to maintain a separate build configuration
just for Windows.
</p>
</li>
<li>
<strong>Reliable detection of file changes using MD5 signatures</strong>
<p>
Use of traditional file timestamps instead of MD5 can be configured.
</p>
</li>
<li>
<strong>Parallel builds</strong>
<p>
Keeps up to N jobs running simultaneously regardless
of directory hierarchy.
</p>
</li>
<li>
<strong>Global view of dependencies</strong>
<p>
Simplifies builds by eliminating multiple passes
or reording targets to build everything correctly.
</p>
</li>
<li>
<strong>Multi-platform configuration (like <tt>Autoconf</tt>)</strong>
<p>
Support for finding <tt>#include</tt> files,
libraries, functions and <tt>typedef</tt> declarations.
</p>
</li>
<li>
<strong>Shared built-file cache</strong>
<p>
Speeds up multiple builds by allowing developers
to share pre-built targets
(like <tt>ccache</tt>, but for any type of target file,
not just C/C++ compilation).
</p>
</li>
</ul>
<!--
<h2></h2>
<p>What are the high-level assumptions or ground rules for the project?
</p>
<p>For example:
</p>
<ul>
<li> we will use programming language X on operating system Y for now.
<li>We will, or will not, consider certain functional areas like
internationalization, high security, concurrency, etc. The list of
functional areas will depend on what you are trying to do.
<li>Try to keep this part short.
</ul>
-->
<h2>Future</h2>
See the <a href="roadmap.html">Roadmap</a> page.
</div>
</body>
</html>
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