Creating a Custom Builder in SCons

Suppose we need to create a custom builder in SCons. This custom builder will read a text file and append an author name at the end of the file.

import os

def my_builder(target, source, env):
    for i in range(0, len(source)):
       txt = open(source[i].abspath).read()
       txt = txt + os.linesep + "Author: " + env['AUTHOR']
       open(target[i].abspath, "wb").write(txt)

env = Environment()
env['BUILDERS']['MyBuilder'] = Builder(action = my_builder)

env.MyBuilder(['output1.txt', 'output2.txt'], ['input1.txt', 'input2.txt'], 
              AUTHOR = "Foo")

The custom builder allows an argument to be passed in into our custom builder. How we pass the argument is by using the Python's keyword argument, e.g. AUTHOR = "Foo". The custom builder function can then read this value from the env, e.g. env["AUTHOR"].