Extract the Nibble from an 8-bit Register

Code

#include <stdio.h>
#include <stdint.h>

unsigned char extractNibble(unsigned char reg, int pos) {
    uint8_t bit_mask = 0x0f;

    if (pos) {
        bit_mask <<= 4;
        return (reg & bit_mask) >> 4;
    }

    return reg & bit_mask;
}

int main() {
    unsigned char reg;
    int pos;
    scanf("%hhu %d", &reg, &pos);
    printf("%d", extractNibble(reg, pos));
    return 0;
}

Solving Approach