4.2.1.c

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>

int main(int argc, char **argv)
{
    if (2 != argc) {
        printf("usage: a.out <pathname>\n");
        exit(-1);
    }

    if (access(*(argv + 1), R_OK) < 0) {
        printf("access error for %s\n", *(argv + 1));
    } else {
        printf("read access OK\n");
    }

    if (open(*(argv + 1), O_RDONLY) < 0) {
        printf("open error for %s\n", *(argv + 1));
    } else {
        printf("open for reading OK\n");
    }

    return 0;
}