printf打印十六进制

int main(){    unsigned char buf[] = "xxx";    int i = 0;    printf("buf:");    for(i = 0; i < strlen(buf); i++)    {        printf("0x%0x", *(buf + i) >> 4 & 0xf)        printf("%0x ", *(buf + i) & 0xf);    }    printf("\n");}