busybox/util-linux/mountpoint.c

/* vi: set sw=4 ts=4: */
/*
 * mountpoint implementation for busybox
 *
 * Copyright (C) 2005 Bernhard Reutner-Fischer
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 *
 * Based on sysvinit's mountpoint
 */
//config:config MOUNTPOINT
//config:	bool "mountpoint (5.1 kb)"
//config:	default y
//config:	help
//config:	mountpoint checks if the directory is a mountpoint.

//applet:IF_MOUNTPOINT(APPLET_NOEXEC(mountpoint, mountpoint, BB_DIR_BIN, BB_SUID_DROP, mountpoint))

//kbuild:lib-$(CONFIG_MOUNTPOINT) += mountpoint.o

//usage:#define mountpoint_trivial_usage
//usage:       "[-q] { [-dn] DIR | -x DEVICE }"
//usage:#define mountpoint_full_usage "\n\n"
//usage:       "Check if DIR is a mountpoint\n"
//usage:     "\n	-q	Quiet"
//usage:     "\n	-d	Print major:minor of the filesystem"
//usage:     "\n	-n	Print device name of the filesystem"
//////// -n is not supported by util-linux-2.36.1 ^^^^^^^^^^^^^^^^^^
//usage:     "\n	-x	Print major:minor of DEVICE"
//usage:
//usage:#define mountpoint_example_usage
//usage:       "$ mountpoint /proc\n"
//usage:       "/proc is not a mountpoint\n"
//usage:       "$ mountpoint /sys\n"
//usage:       "/sys is a mountpoint\n"

#include "libbb.h"

int mountpoint_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mountpoint_main(int argc UNUSED_PARAM, char **argv)
{
	struct stat st;
	const char *msg;
	char *arg;
	int rc, opt;

	opt = getopt32(argv, "^" "qdxn" "\0" "=1");
#define OPT_q (1)
#define OPT_d (2)
#define OPT_x (4)
#define OPT_n (8)
	arg = argv[optind];
	msg = "%s";

	rc = (opt & OPT_x) ? stat(arg, &st) : lstat(arg, &st);
	if (rc != 0)
		goto err;

	if (opt & OPT_x) {
		if (S_ISBLK(st.st_mode)) {
			printf("%u:%u\n", major(st.st_rdev),
						minor(st.st_rdev));
			return EXIT_SUCCESS;
		}
		errno = 0; /* make perror_msg work as error_msg */
		msg = "%s: not a block device";
		goto err;
	}

	errno = ENOTDIR;
	if (S_ISDIR(st.st_mode)) {
		dev_t st_dev = st.st_dev;
		ino_t st_ino = st.st_ino;
		char *p = xasprintf("%s/..", arg);

		if (stat(p, &st) == 0) {
			//int is_mnt = (st_dev != st.st_dev) || (st_dev == st.st_dev && st_ino == st.st_ino);
			int is_not_mnt = (st_dev == st.st_dev) && (st_ino != st.st_ino);

			if (opt & OPT_d)
				printf("%u:%u\n", major(st_dev), minor(st_dev));
			if (opt & OPT_n) {
				const char *d = find_block_device(arg);
				/* name is undefined, but device is mounted -> anonymous superblock! */
				/* happens with btrfs */
				if (!d) {
					d = "UNKNOWN";
					/* TODO: iterate /proc/mounts, or /proc/self/mountinfo
					 * to find out the device name */
				}
				printf("%s %s\n", d, arg);
			}
			if (!(opt & (OPT_q | OPT_d | OPT_n)))
				printf("%s is %sa mountpoint\n", arg, is_not_mnt ? "not " : "");
			return is_not_mnt;
		}
		arg = p;
		/* else: stat had set errno, just fall through */
	}

 err:
	if (!(opt & OPT_q))
		bb_perror_msg(msg, arg);
	return EXIT_FAILURE;
}