# Use of macro-defined printf

# Macro string connection. The macro parameter is interpreted as a string and cannot be directly used in statements. In macro definition

Printf ("% s;/n", # S) will be interpreted

Printf ("% s;/n", "S ")

For example, the following code

# Define TRACE (S) (printf ("% s \ n", # S), S)/* use commas instead of semicolons */
# Include <stdio. h>
# Include <stdlib. h>
# Include <string. h>
Int main ()
{
Int a = 5;
Int B = TRACE ();
Const char * str = "hello ";
Char des [50];
Strcpy (des, TRACE (str ));
Puts (des );
System ("pause ");
Return 0;
}

 

The macro definition is a comma expression, so the value copied to des is the value of S, that is, str.

Note:

Int a = printf ("% s; \ n", "S"), a is equal to the return value of printf, that is, the number of characters printed by printf.

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