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<!--
Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 The SCons Foundation
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-->
<para>
There is a common set of simple tasks that many build configurations rely
on as they become more complex. Most build tools have special
purpose constructs for performing these tasks, but since &SConscript;
files are &Python; scripts, you can use more flexible built-in &Python;
services to perform these tasks. This appendix lists a number of these
tasks and how to implement them in &Python; and &SCons;.
</para>
<example>
<title>Wildcard globbing to create a list of filenames</title>
<programlisting>
files = Glob(wildcard)
</programlisting>
</example>
<example>
<title>Filename extension substitution</title>
<programlisting>
import os.path
filename = os.path.splitext(filename)[0]+extension
</programlisting>
</example>
<example>
<title>Appending a path prefix to a list of filenames</title>
<programlisting>
import os.path
filenames = [os.path.join(prefix, x) for x in filenames]
</programlisting>
</example>
<example>
<title>Substituting a path prefix with another one</title>
<programlisting>
if filename.find(old_prefix) == 0:
filename = filename.replace(old_prefix, new_prefix)
</programlisting>
</example>
<example>
<title>Filtering a filename list to exclude/retain only a specific set
of extensions</title>
<programlisting>
import os.path
filenames = [x for x in filenames if os.path.splitext(x)[1] in extensions]
</programlisting>
</example>
<example>
<title>The "backtick function": run a shell command and capture the
output</title>
<programlisting>import os
output = os.popen(command).read()
</programlisting>
</example>
<example>
<title>Generating source code: how code can be generated and used by SCons</title>
<para>
The Copy builders here could be any arbitrary shell or python function
that produces one or more files. This example shows how to create
those files and use them in &SCons;.
</para>
<scons_example name="ex1">
<file name="SConstruct" printme="1">
#### SConstruct
env = Environment()
env.Append(CPPPATH = "#")
## Header example
env.Append(BUILDERS =
{'Copy1' : Builder(action = 'cat < $SOURCE > $TARGET',
suffix='.h', src_suffix='.bar')})
env.Copy1('test.bar') # produces test.h from test.bar.
env.Program('app','main.cpp') # indirectly depends on test.bar
## Source file example
env.Append(BUILDERS =
{'Copy2' : Builder(action = 'cat < $SOURCE > $TARGET',
suffix='.cpp', src_suffix='.bar2')})
foo = env.Copy2('foo.bar2') # produces foo.cpp from foo.bar2.
env.Program('app2',['main2.cpp'] + foo) # compiles main2.cpp and foo.cpp into app2.
</file>
<file name="main.cpp">
#include "test.h"
</file>
<file name="test.bar">
// nothing here
</file>
<file name="main2.cpp">
//// main2.cpp
</file>
<file name="foo.bar2">
// nothing here
</file>
</scons_example>
<para>
Where main.cpp looks like this:
</para>
<scons_example_file example="ex1" name="main.cpp">
</scons_example_file>
<para>
produces this:
</para>
<scons_output example="ex1">
<scons_output_command>scons -Q</scons_output_command>
</scons_output>
</example>
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