How to use macros in printf function

Question

So I have this macro and a bunch others defined in my header file

#define COL1WIDTH 16

Which I want to use to print something like this:

word  25 Dir1/FileB 129 Sat Jan 1 00:00:02 2011 12 1(x4), 2(x2), 3(x2), 4(x2), 5(x2) 

How does the syntax to get the macro work? Tried a bunch and it keeps screwing up.

Tried this

printf("%COL1WIDTHs\t",index->terms[0].term);

Answer 1

printf("%" #COL1WIDTH "s\\t", ...

在C预处理器中阅读令牌粘贴和字符串化的信息。

Answer 2

Macros aren't expanded inside strings. Here there's a decent workaround — write

printf("%*s\t", COL1WIDTH, index -> terms[0].term);

and COL1WIDTH will be used in place of the * .

Answer 3

Modify your code as below and it will serve the purpose

#define COL1WIDTH "16"    //define the constant in double quotes

printf("%"COL1WIDTH"s\t",index->terms[0].term); //place macro out of quotes so it can expand            
                                                //during the precompilation