Extract a Bit Field from a 32-bit Register

#include <stdio.h>
#include <stdint.h>
uint32_t extract_bitfield(uint32_t reg, int pos, int len){
    uint32_t mask=(1U<<len)-1;
    return(reg>>pos)&mask;
}
int main(){
    uint32_t reg;
    int pos,len;
    scanf("%u %d %d", &reg,&pos,&len);
    printf("%u", extract_bitfield(reg,pos,len));
    return 0;
}