1LIBBLKID(3)                   Programmer's Manual                  LIBBLKID(3)
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NAME

6       libblkid - block device identification library
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SYNOPSIS

9       #include <blkid.h>
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11       cc file.c -lblkid
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DESCRIPTION

14       The libblkid library is used to identify block devices (disks) as to
15       their content (e.g., filesystem type) as well as extracting additional
16       information such as filesystem labels/volume names, unique
17       identifiers/serial numbers. A common use is to allow use of LABEL= and
18       UUID= tags instead of hard-coding specific block device names into
19       configuration files.
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21       The low-level part of the library also allows the extraction of
22       information about partitions and block device topology.
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24       The high-level part of the library keeps information about block
25       devices in a cache file and is verified to still be valid before being
26       returned to the user (if the user has read permission on the raw block
27       device, otherwise not). The cache file also allows unprivileged users
28       (normally anyone other than root, or those not in the "disk" group) to
29       locate devices by label/id. The standard location of the cache file can
30       be overridden by the environment variable BLKID_FILE.
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32       In situations where one is getting information about a single known
33       device, it does not impact performance whether the cache is used or not
34       (unless you are not able to read the block device directly).
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36       The high-level part of the library supports two methods to determine
37       LABEL/UUID. It reads information directly from a block device or read
38       information from /dev/disk/by-* udev symlinks. The udev is preferred
39       method by default.
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41       If you are dealing with multiple devices, use of the cache is highly
42       recommended (even if empty) as devices will be scanned at most one time
43       and the on-disk cache will be updated if possible.
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45       In some cases (modular kernels), block devices are not even visible
46       until after they are accessed the first time, so it is critical that
47       there is some way to locate these devices without enumerating only
48       visible devices, so the use of the cache file is required in this
49       situation.
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CONFIGURATION FILE

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

57       libblkid was written by Andreas Dilger for the ext2 filesystem
58       utilities, with input from Ted Ts’o. The library was subsequently
59       heavily modified by Ted Ts’o.
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61       The low-level probing code was rewritten by Karel Zak.
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COPYING

64       libblkid is available under the terms of the GNU Library General Public
65       License (LGPL), version 2 (or at your discretion any later version).
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SEE ALSO

68       blkid(8), findfs(8)
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REPORTING BUGS

71       For bug reports, use the issue tracker at
72       https://github.com/util-linux/util-linux/issues.
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AVAILABILITY

75       The libblkid library is part of the util-linux package since version
76       2.15. It can be downloaded from Linux Kernel Archive
77       <https://www.kernel.org/pub/linux/utils/util-linux/>.
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81util-linux 2.38.1                 2022-08-04                       LIBBLKID(3)
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