A program from apue.#include apue.h#include <fcntl.h>int main(int argc, char *argv[]){    if(argc!=2)        err_quit(usage: a.out <pathname>);    if(access(argv[1], R_OK)<0)        err_ret(access error for %s,argv[1]);    else        printf(read access OK\n);    if (open(argv[1], O_RDONLY)) {        err_ret(open error for %s, argv[1]);    } else {        printf(open for reading OK\n);    }    return 0;}I compiled it to an executable named 4-2 and I changed the owner and set the suid this is the output of ls -l:-rwsr-xr-x 1 root sinners 8490 Jan  7 18:50 4-2*and /etc/shadow:-rw------- 1 root root 421 Jan  4 01:29 /etc/shadowBut when I run it:user% ./4-2 /etc/shadow access error for /etc/shadow: Permission deniedopen error for /etc/shadow: Permission deniedCan someone explain why I am getting these access and open errors?
suid-root doesn't have effect
permissions;files;not root user