beneath.c

/* $Id: beneath.c,v 1.1 2018/10/13 16:53:02 kostik Exp kostik $ */

#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#ifndef O_BENEATH
#define	O_BENEATH	0x00400000	/* Fail if not under cwd */
#define	AT_BENEATH		0x1000	/* Fail if not under dirfd */
#endif

int
main(int argc, char *argv[])
{
	struct stat st;
	char *name;
	int error, fd, i;

	for (i = 1; i < argc; i++) {
		name = argv[i];
		fd = open(name, O_RDONLY | O_BENEATH);
		if (fd == -1) {
			fprintf(stderr, "open(\"%s\") failed, error %d %s\n",
			    name, errno, strerror(errno));
		} else {
			fprintf(stderr, "open(\"%s\") succeeded\n", name);
			close(fd);
		}
		error = fstatat(AT_FDCWD, name, &st, AT_BENEATH);
		if (error == -1){
			fprintf(stderr, "stat(\"%s\") failed, error %d %s\n",
			    name, errno, strerror(errno));
		} else {
			fprintf(stderr, "stat(\"%s\") succeeded\n", name);
		}
	}
}