SCNu8

SCNu8 is a macro defined in the C standard header inttypes.h used to format input of unsigned 8-bit integers with the scanf family. It is part of a family of macros (SCNd8, SCNu8, SCNo8, SCNx8) that provide portable length modifiers for fixed-width integer types, in this case uint8_t.

The macro expands to a string that represents the appropriate length modifier and conversion specification for reading a uint8_t value in decimal form. When concatenated with a percent sign, it yields a complete scanf format specifier. For example, on many platforms where uint8_t is an unsigned char, SCNu8 expands to hhu, making the format "%hhu".

Usage example:

#include <stdio.h>

#include <stdint.h>

#include <inttypes.h>

uint8_t val;

scanf("%" SCNu8, &val);

SCNu8 is specifically for decimal input. There are corresponding macros for other bases, such as SCNo8 for octal and SCNx8 for hexadecimal, and SCNd8 for signed decimal input.

For printing, a separate family of macros (PRIu8, PRIx8, etc.) is used with printf to ensure portable output of uint8_t values.

These macros help ensure portability across platforms where the exact underlying type of uint8_t may vary, by tying the format specification to the actual width of the type.