limiting the number of chars scanf will read using a define value

Question

I want to limit the number of chars scanf command will get using a define value. The following code worked well

scanf("%20s",&stud->student_name);

but then i have tried that one (MAXNAMELEN is defiend as 20)

scanf("%MAXNAMELENs",&stud->student_name);

and it didn't work. how can I do that using scanf only ?

Answer 1

A pair of defines allow for stringifying another define

#define MAXNAMELEN 20
#define LENSTR_(x) #x
#define LENSTR(x) LENSTR_(x)

use as

char str[MAXNAMELEN + 1] = "";
result = scanf ( "%"LENSTR(MAXNAMELEN)"s", str);