test.c

#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>

static void check_access(const char *path) {
	int ret = access(path, F_OK);
	if (ret == -1) {
		int e = errno;
		printf("access '%s' failed: %s\n", path, strerror(e));
	} else {
		printf("access '%s' ok\n", path);
	}
}

int main(void) {
	check_access(""); /* outputs (for me): access '' failed: No such file or directory */
	check_access("/"); /* outputs (for me): access '/' ok */
	check_access("/root"); /* outputs (for me): access '/root' ok */
	check_access("/root/."); /* outputs (for me): access '/root/.' failed: Permission denied */
	return 0;
}