預處理器常用變量

The following are preprocessor variables and part of the C/C++ standard. During preprocessing, they are replaced respectively by a constant string  or a  integer .

• '__DATE__'                 -> a string literal of the form "Mmm dd yyyy"
  
• '__TIME__'                   -> a string literal of the form "hh:mm:ss"
  
• '__TIMESTAMP__'     -> a string literal of the form "Mmm dd yyyy hh:mm:ss"
  
• '__FUNCTION__'        -> a string literal which contains the function name (this is part of C99, the new C standard and not all C++ compilers support it)
• '__FILE__'                   ->  a string literal holding the current file name
• '__LINE__'                   ->  a integer representing the current line number.

在程序中可以直接使用這些宏。

例如：

printf("Filename:%10s  Line: %s ",__FILE__,__LINE__);