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SCons / ReplacementBuilder

This is a builder to help when you need to take a file and replace certain variables in it. (See also SubstInFileBuilder for another approach which may do better handling changes in the variable values.)

For example, when creating pkg-config files, autoconf will take a package.pc.in file and create package.pc from it, replacing things such as @libdir@ with the actual value.

We can do much better :-)


from string import Template

def replace_action(target, source, env):
    open(str(target[0]), 'w').write(Template(open(str(source[0]), 'r').read()).safe_substitute(env))
    return 0

def replace_string(target, source, env):
    return "building '%s' from '%s'" % (str(target[0]), str(source[0]))

def generate(env, **kw):
    action = env.Action(replace_action, replace_string)
    env['BUILDERS']['ScanReplace'] = env.Builder(action=action, src_suffix='.in', single_source=True)

def exists(env):
    return 1

To use this, place scanreplace.py into your tools directory (see the manpage for more details) and then do this:

env = Environment(tools=['default', 'scanreplace'], toolpath=['tools'])
env['prefix'] = '/usr/local'

This will create myprogram.pc from myprogram.pc.in, replacing variables along the way.

Variables will be found in the environment, so in the previous example, any occurence of '$prefix' or '${prefix}' in myprogram.pc.in would be replaced with '/usr/local'.

Have fun!