LIBBLKID(3)							Programmer's Manual						       LIBBLKID(3)

NAME

       libblkid - block device identification library

SYNOPSIS

       #include <blkid.h>

       cc file.c -lblkid

DESCRIPTION

       The libblkid library is used to identify block devices (disks) as to their content (e.g.  filesystem type) as well as extracting additional
       information such as filesystem labels/volume names, unique identifiers/serial numbers.  A common use is to allow use of	LABEL=	and  UUID=
       tags instead of hard-coding specific block device names into configuration files.

       The low-level part of the library also allows to extract information about partitions and block device topology.

       The  high-level	part  of  the library keeps information about block devices in a cache file and is verified to still be valid before being
       returned to the user (if the user has read permission on the raw block device, otherwise not).  The cache  file	also  allows  unprivileged
       users  (normally  anyone  other	than  root, or those not in the "disk" group) to locate devices by label/id.  The standard location of the
       cache file can be overridden by the environment variable BLKID_FILE.

       In situations where one is getting information about a single known device, it does not impact performance whether the cache is used or not
       (unless you are not able to read the block device directly).

       The  high-level part of the library supports two methods to evaluate LABEL/UUID.  It reads information directly from a block device or read
       information from /dev/disk/by-* udev symlinks. The udev is preferred method by default.

       If you are dealing with multiple devices, use of the cache is highly recommended (even if empty) as devices will be  scanned  at  most  one
       time and the on-disk cache will be updated if possible.

       In  some  cases	(modular kernels), block devices are not even visible until after they are accessed the first time, so it is critical that
       there is some way to locate these devices without enumerating only visible devices, so the use of the cache file is required in this situa-
       tion.

CONFIGURATION FILE

       The  standard  location of the /etc/blkid.conf config file can be overridden by the environment variable BLKID_CONF. For more details about
       the config file see blkid(8) man page.

AUTHOR

       libblkid was written by Andreas Dilger for the ext2 filesystem utilties, with input from Ted Ts'o.  The library	was  subsequently  heavily
       modified by Ted Ts'o.

       The low-level probing code was rewritten by Karel Zak.

COPYING

       libblkid  is  available	under  the terms of the GNU Library General Public License (LGPL), version 2 (or at your discretion any later ver-
       sion).

SEE ALSO

       blkid(8), findfs(8)

AVAILABILITY

       libblkid is part of the util-linux package since version 2.15 and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux							     May 2009							       LIBBLKID(3)