Note for SCons 3.0.1 User Guide, CH2 Simple Builds

SCons是一個用Python的新一代軟體建構工具(SCons is a next-generation software construction tool)，就像Make一樣可以建構軟體的工具。

CH 2.1. Build Simple C/C++ Programs

主要依具名為SConstruct的檔案進行建構，最小的SConstruct內容如下

Program('hello.c') 

這裡面包含兩個資訊，你要建構的程式名稱(hello)，以及從哪個檔案建構(hello.c)，"Program"在文中被稱為builder_method，主要用於告訴SCons要建構執行檔。

% scons scons: Reading SConscript files ... 
scons: done reading SConscript files. 
scons: Building targets ... 
cc -o hello.o -c hello.c 
cc -o hello hello.o 
scons: done building targets.

CH 2.2. Building Object Files

Object('hello.c') 

Objcet這個builder method用於告訴SCons如何從指定的source files中建立一個Object file

% scons scons: Reading SConscript files ... 
scons: done reading SConscript files. 
scons: Building targets ... 
cc -o hello.o -c hello.c 
scons: done building targets.

2.4. Cleaning Up After a Build

在SCons清除(Cleaning Up)一個build只需要在scons後面新增"-c"/"--clean"即可

2.5. The SConstruct File

SConstruct之於SCons就等同於Makefile之於Make，而SConstruct是個Python Script，注意，SConstruct的順序並非SCons實際執行的順序 比如該SConstruct的內容與其執行結果分別為

print("Calling Program('hello.c')") 
Program('hello.c') 
print("Calling Program('goodbye.c')") 
Program('goodbye.c') 
print("Finished calling Program()") 

hello.c先被呼叫，而後才是goodbye.c

% scons 
scons: Reading SConscript files ... 
Calling Program('hello.c') 
Calling Program('goodbye.c') 
Finished calling Program() 
scons: done reading SConscript files. 
scons: Building targets ... 
cc -o goodbye.o -c goodbye.c 
cc -o goodbye goodbye.o 
cc -o hello.o -c hello.c 
cc -o hello hello.o 
scons: done building targets. 

goodbye先被建置，而後才是hello

2.6. Making the SCons Output Less Verbose

參數"-Q"可以讓SCons輸出較少的建置訊息

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

brook@vista:~$ scons -c
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Cleaning targets ...
Removed hello.o
scons: done cleaning targets.

brook@vista:~$ scons
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
gcc -o hello.o -c hello.c
scons: done building targets.

參考資料：
• SCons 3.0.1 User Guide