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.
Example E.2. Filename extension substitution
import os.path filename = os.path.splitext(filename)[0]+extension
Example E.3. Appending a path prefix to a list of filenames
import os.path filenames = [os.path.join(prefix, x) for x in filenames]
Example E.4. Substituting a path prefix with another one
if filename.find(old_prefix) == 0:
filename = filename.replace(old_prefix, new_prefix)
Example E.5. Filtering a filename list to exclude/retain only a specific set of extensions
import os.path filenames = [x for x in filenames if os.path.splitext(x)[1] in extensions]
Example E.6. The "backtick function": run a shell command and capture the output
import subprocess output = subprocess.check_output(command)
Example E.7. Generating source code: how code can be generated and used by SCons
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.
#### 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.
Where main.cpp looks like this:
#include "test.h"
produces this:
% scons -Q
cc -o app main.cpp
cat < foo.bar2 > foo.cpp
cc -o app2 main2.cpp foo.cpp
cat < test.bar > test.h