Reading a specific string using Scanf() - c

Question

I'm triying to read a string with a specific format in C using scanf()
The string has the format:
<LET,LET,LET> op
where LET is a capital letter and op has to be '+' or '%'.
These are valid entries:
<A,B,C> +
<A,W,Z> %
<Q, X,W> +
These are not:
<A,b,C> +
<A,W,Zddddd> %
<Q,X,W> *
I'm trying something like this
#include <stdio.h>
int ret = 0;
char str[8];
ret = scanf("%8[^\n]",str);
but str ends up with garbage. I just don't know how to read it and how to get only capital letters.
Thanks

Answer 1

try this:
#include <stdio.h>
int main(void) {
char let1[2], let2[2], let3[2], op[2];
char line[80];
while(fgets(line, sizeof line, stdin)){
if(sscanf(line, "<%1[A-Z], %1[A-Z], %1[A-Z]> %1[+%]", let1, let2, let3, op) == 4)
puts("valid");
else
puts("invalid");
}
return 0;
}

Answer 2

This method also detects trail garbage on the line.
"%n" saves the offset of the current scan. Only if n is non-zero and indexes '\0' was there success.
By using string literal concatenation, code can clearly show what format is being used for the various parts of the scan.
#include <stdio.h>
#define F_LET " %1[A-Z]"
#define F_SEP " ,"
#define F_OP " %1[+%]"
int main(void) {
char buf[100];
while (fgets(buf, sizeof buf, stdin)) {
char let[3][2];
char op[2];
int n = 0;
sscanf(buf, " <" F_LET F_SEP F_LET F_SEP F_LET " >" F_OP " %n",
let[0], let[1], let[2], op, &n);
puts((n && buf[n] == '\0') ? "Success" : "Fail");
}
}

Answer 3

An alternative to BLUEPIXY's perfectly good answer, is to simply use char, and scan the input using %c instead, e.g.:
#include <stdio.h>
#include <ctype.h>
int main()
{
char let1, let2, let3, op;
char line[80]; // or some other suitable size
while (fgets(line, sizeof line, stdin))
{
if (sscanf(line, "< %c , %c , %c > %c", &let1, &let2, &let3, &op) == 4 && (op == '+' || op == '%') && isupper(let1) && isupper(let2) && isupper(let3))
{
printf("valid!\nlet1 = %c\nlet2 = %c\nlet3 = %c\nop = %c\n", let1, let2, let3, op);
}
else
{
puts("invalid");
}
}
}
Note that the spaces before and after the %c are important as they allow sscanf to gobble up all whitespace before trying to match the %c or the comma.
Unlike BLUEPIXY's answer however, we have to check that op matches + or % manually.
EDIT: I missed the part where the LET characters must be uppercase. I've fixed the answer, but of course, it is now more complicated.