On Sat, Sep 08, 2012 at 06:07:51PM +0000, Amit wrote:
> Hello,
>
> I have a simple program using libmount that simply gets the path of the
> root filesystem. I can't seem to get it to work. I always get a
> segmentation fault. There is probably something basic that I am missing
> but can't figure it out.
>
> #include <stdlib.h>
> #include <string.h>
> #include <stdio.h>
> #include <assert.h>
>
> #include <libmount.h>
>
> int main(int argc, char *argv[])
> {
> struct libmnt_context *cxt;
> struct libmnt_table *tab;
> struct libmnt_fs *fs;
>
> /* Enable debugging */
> mnt_init_debug(0xffff);
>
> /* Create new mount context */
> cxt = mnt_new_context();
> if (!cxt)
> printf("Error creating new mount context\n");
>
> /* A mount table */
> if (mnt_context_get_mtab(cxt, &tab) < 0)
> printf("Error getting mtab\n");
>
> /* Get the root filesystem */
> if (mnt_table_get_root_fs(tab, &fs) == -1)
if (mnt_table_get_root_fs(tab, &fs) != 0)
Sorry, the docs for the function is incorrect. Almost all libmount
functions return zero on success and less than zero on error.
Note that mnt_table_get_root_fs() uses mountpoint Id and parent Id
from /proc/self/mountinfo to found root fs.
It means that you have to use the mountinfo file -- on systems with
regular mtab file the function mnt_context_get_mtab() parses /etc/mtab
rather than the mountinfo file.
tab = mnt_new_table_from_file("/proc/self/mountinfo");
if (tab && mnt_table_get_root_fs(tab, &fs) == 0)
....
the struct libmnt_context is unnecessary in this case.
The mnt_table_get_root_fs() is mostly designed for application where
you need to sort mountpoints to a tree. (for example findmnt(8))
If you not sure than mnt_table_find_target() is probably better
choice.
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
http://karelzak.blogspot.com
--
To unsubscribe from this list: send the line "unsubscribe util-linux" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
