sys-utils/mountpoint.c

/*
 * mountpoint(1) - see if a directory is a mountpoint
 *
 * This is libmount based reimplementation of the mountpoit(1)
 * from sysvinit project.
 *
 *
 * Copyright (C) 2011 Red Hat, Inc. All rights reserved.
 * Written by Karel Zak <kzak@redhat.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <getopt.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>

#include <libmount.h>

#include "nls.h"
#include "xalloc.h"
#include "c.h"
#include "closestream.h"
#include "pathnames.h"

static int quiet;

static int dir_to_device(const char *spec, dev_t *dev)
{
	struct libmnt_table *tb = mnt_new_table_from_file(_PATH_PROC_MOUNTINFO);
	struct libmnt_fs *fs;
	struct libmnt_cache *cache;
	int rc = -1;

	if (!tb) {
		/*
		 * Fallback. Traditional way to detect mountpoints. This way
		 * is independent on /proc, but not able to detect bind mounts.
		 */
		struct stat pst, st;
		char buf[PATH_MAX], *cn;
		int len;

		if (stat(spec, &st) != 0)
			return -1;

		cn = mnt_resolve_path(spec, NULL);	/* canonicalize */

		len = snprintf(buf, sizeof(buf), "%s/..", cn ? cn : spec);
		free(cn);

		if (len < 0 || (size_t) len + 1 > sizeof(buf))
			return -1;
		if (stat(buf, &pst) !=0)
			return -1;

		if ((st.st_dev != pst.st_dev) ||
		    (st.st_dev == pst.st_dev && st.st_ino == pst.st_ino)) {
			*dev = st.st_dev;
			return 0;
		}

		return -1;
	}

	/* to canonicalize all necessary paths */
	cache = mnt_new_cache();
	mnt_table_set_cache(tb, cache);
	mnt_unref_cache(cache);

	fs = mnt_table_find_target(tb, spec, MNT_ITER_BACKWARD);
	if (fs && mnt_fs_get_target(fs)) {
		*dev = mnt_fs_get_devno(fs);
		rc = 0;
	}

	mnt_unref_table(tb);
	return rc;
}

static int print_devno(const char *devname, struct stat *st)
{
	struct stat stbuf;

	if (!st && stat(devname, &stbuf) == 0)
		st = &stbuf;
	if (!st)
		return -1;
	if (!S_ISBLK(st->st_mode)) {
		if (!quiet)
			warnx(_("%s: not a block device"), devname);
		return -1;
	}
	printf("%u:%u\n", major(st->st_rdev), minor(st->st_rdev));
	return 0;
}

static void __attribute__((__noreturn__)) usage(FILE *out)
{
	fputs(USAGE_HEADER, out);
	fprintf(out,
	      _(" %1$s [-qd] /path/to/directory\n"
		" %1$s -x /dev/device\n"), program_invocation_short_name);

	fputs(USAGE_OPTIONS, out);
	fputs(_(" -q, --quiet        quiet mode - don't print anything\n"
		" -d, --fs-devno     print maj:min device number of the filesystem\n"
		" -x, --devno        print maj:min device number of the block device\n"), out);
	fputs(USAGE_SEPARATOR, out);
	fputs(USAGE_HELP, out);
	fputs(USAGE_VERSION, out);
	fprintf(out, USAGE_MAN_TAIL("mountpoint(1)"));

	exit(out == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
}

int main(int argc, char **argv)
{
	int c, fs_devno = 0, dev_devno = 0, rc = 0;
	char *spec;
	struct stat st;

	static const struct option longopts[] = {
		{ "quiet", 0, 0, 'q' },
		{ "fs-devno", 0, 0, 'd' },
		{ "devno", 0, 0, 'x' },
		{ "help", 0, 0, 'h' },
		{ "version", 0, 0, 'V' },
		{ NULL, 0, 0, 0 }
	};

	setlocale(LC_ALL, "");
	bindtextdomain(PACKAGE, LOCALEDIR);
	textdomain(PACKAGE);
	atexit(close_stdout);

	mnt_init_debug(0);

	while ((c = getopt_long(argc, argv, "qdxhV", longopts, NULL)) != -1) {

		switch(c) {
		case 'q':
			quiet = 1;
			break;
		case 'd':
			fs_devno = 1;
			break;
		case 'x':
			dev_devno = 1;
			break;
		case 'h':
			usage(stdout);
			break;
		case 'V':
			printf(UTIL_LINUX_VERSION);
			return EXIT_SUCCESS;
		default:
			usage(stderr);
			break;
		}
	}

	if (optind + 1 != argc)
		usage(stderr);

	spec = argv[optind++];

	if (stat(spec, &st)) {
		if (!quiet)
			err(EXIT_FAILURE, "%s", spec);
		return EXIT_FAILURE;
	}
	if (dev_devno)
		rc = print_devno(spec, &st);
	else {
		dev_t src;

		if (!S_ISDIR(st.st_mode)) {
			if (!quiet)
				errx(EXIT_FAILURE, _("%s: not a directory"), spec);
			return EXIT_FAILURE;
		}

		if ( dir_to_device(spec, &src)) {
			if (!quiet)
				printf(_("%s is not a mountpoint\n"), spec);
			return EXIT_FAILURE;
		}
		if (fs_devno)
			printf("%u:%u\n", major(src), minor(src));
		else if (!quiet)
			printf(_("%s is a mountpoint\n"), spec);
	}

	return rc ? EXIT_FAILURE : EXIT_SUCCESS;
}