Note for SCons 3.0.1 User Guide, CH3 Less Simple Things to Do With Builds

3.1. Specifying the Name of the Target (Output) File

當你呼叫Program()時，Scons會build出跟source file一樣檔名的程式，如果要build不同檔名的程式，可以Program()左邊參數放檔名，右邊放source file

brook@vista:~/scons/03.1$ cat SConstruct
Program('new_hello', 'hello.c')

brook@vista:~/scons/03.1$ scons -Q
gcc -o hello.o -c hello.c
gcc -o new_hello hello.o
brook@vista:~/scons/03.1$ scons -c -Q
Removed hello.o
Removed new_hello

3.2. Compiling Multiple Source Files

如果要從多個source file建立程式，只需在Program()放置python list，則會建立以第一個source file為檔名的程式檔

brook@vista:~/scons/03.1$ cat SConstruct
Program(['hello.c', 'a.c'])

brook@vista:~/scons/03.1$ scons -Q
gcc -o a.o -c a.c
gcc -o hello.o -c hello.c
gcc -o hello hello.o a.o

如果要建立不同程式名稱，只需在Program()左邊參數放檔名，右邊放source file list即可

brook@vista:~/scons/03.1$ cat SConstruct
Program('new_hello', ['hello.c', 'a.c'])

brook@vista:~/scons/03.1$ scons -Q
gcc -o a.o -c a.c
gcc -o hello.o -c hello.c
gcc -o new_hello hello.o a.o

3.3. Making a list of files with Glob

你可以適用Glob()來找尋matching的檔案，其語法可以使用*, ? and [abc]等shell的regular expression

brook@vista:~/scons/03.02$ cat SConstruct
Program('new_hello', Glob("*.c"))

brook@vista:~/scons/03.02$ scons -Q
gcc -o a.o -c a.c
gcc -o hello.o -c hello.c
gcc -o new_hello a.o hello.o

3.4. Specifying Single Files Vs. Lists of Files

SCons將所有source file視為list，只要符合list即可

# The following two calls both work correctly: 
Program('program1', 'program1.c') 
Program('program2', ['program2.c'])

common_sources = ['file1.c', 'file2.c'] 

# THE FOLLOWING IS INCORRECT AND GENERATES A PYTHON ERROR 
# BECAUSE IT TRIES TO ADD A STRING TO A LIST: 
Program('program1', common_sources + 'program1.c') 

# The following works correctly, because it's adding two 
# lists together to make another list. 
Program('program2', common_sources + ['program2.c'])

3.5. Making Lists of Files Easier to Read

SCons中的Split()可以將字串內的檔案換成list，讓developer寫一個容易閱讀的list

brook@vista:~/scons/03.4$ cat SConstruct
print('a.c b.c c.c')
print(Split('a.c b.c c.c'))
src_files = Split('a.c b.c c.c')
print(src_files)

brook@vista:~/scons/03.4$ scons -Q
a.c b.c c.c
['a.c', 'b.c', 'c.c']
['a.c', 'b.c', 'c.c']
scons: `.' is up to date.

3.6. Keyword Arguments

Python預設是positional argument(位置參數)，是按順序傳入function。關鍵字參數（keyword argument），顧名思義是以關鍵字方式傳入，使用keyword argument時，對順序沒有要求。Program(target, source)

src_files = Split('main.c file1.c file2.c') 
Program(target = 'program', source = src_files)

src_files = Split('main.c file1.c file2.c') 
Program(source = src_files, target = 'program')

3.7. Compiling Multiple Programs

如果要編譯多個程式，只需多描述幾行Program()即可

brook@vista:~/scons/03.7$ cat SConstruct
Program('a.c')
Program('b.c')

brook@vista:~/scons/03.7$ scons -Q
gcc -o a.o -c a.c
gcc -o a a.o
gcc -o b.o -c b.c
gcc -o b b.o

3.8. Sharing Source Files Between Multiple Programs

SCons會自行判斷build的dependence，所以你只需照實描述各個program所需的source file即可

brook@vista:~/scons/03.7$ cat SConstruct
Program('a', ['a.c', 'comm.c'])
Program('b', ['b.c', 'comm.c'])

brook@vista:~/scons/03.7$ scons -Q
gcc -o a.o -c a.c
gcc -o comm.o -c comm.c
gcc -o a a.o comm.o
gcc -o b.o -c b.c
gcc -o b b.o comm.o

3.9. Overriding construction variables when calling a Builder

當你在呼叫這些builder時，Scons允許你帶入一些參數或覆蓋原本的參數，如 adds 'include' to $CPPPATH, 'EBUG' to $CPPDEFINES, and 'm' to $LIBS.

Program('hello', 'hello.c', parse_flags = '-Iinclude -DEBUG -lm')

參考資料：
• SCons 3.0.1 User Guide