Note for SCons 3.0.3 User Guide, CH5 Node Objects

所有的檔案與目錄在SCons中都被視為"Nodes"，善用"Node"可以使您的SConscript文件可移植且易於閱讀。

5.1. Builder Methods Return Lists of Target Nodes

所有builder methods都回傳一個Node list，用於辨識要構建的目標文件。這Node list可作為參數傳遞給其他builder methods。

brook@vista:~/scons/04.7$ cat SConstruct
a_list = Object('a.c', CCFLAGS='-DHELLO')
b_list = Object('b.c', CCFLAGS='-DWORLD')
Program(a_list + b_list)
 
brook@vista:~/scons/04.7$ scons -Q
gcc -o a.o -c -DHELLO a.c
gcc -o b.o -c -DWORLD b.c
gcc -o a a.o b.o

5.2. Explicitly Creating File and Directory Nodes

SCons的File()與Dir()可回傳file或directory Node，而Entry()可回傳file或directory Node。

hello_c = File('hello.c')
Program(hello_c)
 
classes = Dir('classes')
Java(classes, 'src')
 
xyzzy = Entry('xyzzy')

5.3. Printing Node File Names

您可以對Node執行print，打Node所代表的檔名。

brook@vista:~/scons/05.3$ cat SConstruct
object_list = Object(['a.c', 'b.c'])
program_list = Program(object_list)
print("The object file is: %s"%object_list)
print("The program file is: %s"%program_list[0])

brook@vista:~/scons/05.3$ scons -Q
The object file is: ['a.o', 'b.o']
The program file is: a
scons: `.' is up to date.

5.4. Using a Node's File Name as a String

您可以使用Python的str函數將Node轉成字串加以處理。

brook@vista:~/scons/05.5$ cat SConstruct
import os
object_list = Object(['a.c', 'b.c'])
obj_str = str(object_list[0])
print("The object file is: %s"% obj_str)
if not os.path.exists(obj_str):
    print("%s does not exist!"% obj_str)
else:
    print("%s exist!"% obj_str)
brook@vista:~/scons/05.5$ scons -Q
The object file is: a.o
a.o exist!
scons: `.' is up to date.

5.5. GetBuildPath: Getting the Path From a Node or String

env.GetBuildPath(file_or_list)可以用來取得file/Node的路徑。

brook@vista:~/scons/05.6$ cat SConstruct
object_list = Object(['a.c', 'b.c'])
env=Environment(VAR="value")
n=File("foo.c")
print(env.GetBuildPath([n, "sub/dir/$VAR", '/tmp'] + object_list))
brook@vista:~/scons/05.6$ scons -Q
['foo.c', 'sub/dir/value', '/tmp', 'a.o', 'b.o']
scons: `.' is up to date.

參考資料：
• SCons 3.0.3 User Guide