shell: use uint8_t instead of char for showing bytes

source/shell.c

@@ -54,14 +54,14 @@ static void parse_hex(FILE *fp, char *buf, size_t len)
 static void print_hex_ascii(const char *buf, size_t len)
 {
 	size_t n, i;
-	char c;
+	uint8_t c;
 
 	for (; len; buf += n, len -= n) {
 		n = min(len, 16);
 		
 		for (i = 0; i < 16; ++i) {
 			c = (i < n) ? buf[i] : 0;
-			printf("%02x", c);
+			printf("%x", c);
 		}
 
 		printf(" ");