blkid: create basic directories
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
parent
525dd31635
commit
24a06aeb1b
|
@ -6,6 +6,7 @@ SUBDIRS = \
|
|||
fdisk \
|
||||
getopt \
|
||||
lib \
|
||||
libs \
|
||||
login-utils \
|
||||
misc-utils \
|
||||
po \
|
||||
|
|
|
@ -709,6 +709,8 @@ getopt/Makefile
|
|||
hwclock/Makefile
|
||||
include/Makefile
|
||||
lib/Makefile
|
||||
libs/Makefile
|
||||
libs/blkid/Makefile
|
||||
login-utils/Makefile
|
||||
misc-utils/Makefile
|
||||
mount/Makefile
|
||||
|
|
|
@ -0,0 +1 @@
|
|||
SUBDIRS = blkid
|
|
@ -0,0 +1,3 @@
|
|||
include $(top_srcdir)/config/include-Makefile.am
|
||||
|
||||
EXTRA_DIST = README.fsprobe
|
|
@ -0,0 +1,78 @@
|
|||
libblkid - a library to handle device identification and token extraction
|
||||
|
||||
Basic usage is as follows - there are two normal usage patterns:
|
||||
|
||||
For cases where a program wants information about multiple devices, or
|
||||
expects to be doing multiple token searches, the program should
|
||||
directly initialize cache file via (second parameter is cache
|
||||
filename, NULL = default):
|
||||
|
||||
blkid_cache cache = NULL;
|
||||
if (blkid_get_cache(&cache, NULL) < 0)
|
||||
/* error reading the cache file, not really fatal */
|
||||
|
||||
Note that if no cache file exists, an empty cache struct is still
|
||||
allocated. Usage of libblkid functions will use the cache to avoid
|
||||
needless device scans.
|
||||
|
||||
The model of the blkid cache is that each device has a number of
|
||||
attributes that can be associated with it. Currently the attributes
|
||||
which are supported (and set) by blkid are:
|
||||
|
||||
TYPE filesystem type
|
||||
UUID filesystem uuid
|
||||
LABEL filesystem label
|
||||
|
||||
|
||||
How to use libblkid? Normally, you either want to find a device with
|
||||
a specific NAME=value token, or you want to output token(s) from a
|
||||
device. To find a device that matches a following attribute, you
|
||||
simply call the blkid_get_devname() function:
|
||||
|
||||
if ((devname = blkid_get_devname(cache, attribute_name, value))) {
|
||||
/* do something with devname */
|
||||
string_free(devname);
|
||||
}
|
||||
|
||||
The cache parameter is optional; if it is NULL, then the blkid library
|
||||
will load the default blkid.tab cache file, and then release the cache
|
||||
before function call returns. The return value is an allocated string
|
||||
which holds the resulting device name (if it is found). If the value
|
||||
is NULL, then attribute_name is parsed as if it were
|
||||
"<attribute_name>=<value>"; if it cannot be so parsed, then the
|
||||
original attribute_name is returned in a copied allocated string.
|
||||
This is a convenience to allow user programs to want to translate user
|
||||
input, whether it is of the form: "/dev/hda1", "LABEL=root",
|
||||
"UUID=082D-26E3", and get back a device name that it can use.
|
||||
|
||||
Alternatively, of course, the programmer can pass an attribute name of
|
||||
"LABEL", and value of "root", if that is more convenient.
|
||||
|
||||
Another common usage is to retrieve the value of a specific attribute
|
||||
for a particular device. This can be used to determine the filesystem
|
||||
type, or label, or uuid for a particular device:
|
||||
|
||||
if ((value = blkid_get_tag_value(cache, attribute_name, devname))) {
|
||||
/* do something with value */
|
||||
string_free(value);
|
||||
}
|
||||
|
||||
If a program needs to call multiple blkid functions, then passing in a
|
||||
cache value of NULL is not recommended, since the /etc/blkid.tab file
|
||||
will be repeatedly parsed over and over again, with memory allocated
|
||||
and deallocated. To initialize the blkid cache, blkid_get_cache()
|
||||
function is used:
|
||||
|
||||
if (blkid_get_cache(&cache, NULL) < 0)
|
||||
goto errout;
|
||||
|
||||
The second parameter of blkid_get_cache (if non-zero) is the alternate
|
||||
filename of the blkid cache file (where the default is
|
||||
/etc/blkid.tab). Normally, programs should just pass in NULL.
|
||||
|
||||
If you have called blkid_get_cache(), you should call blkid_put_cache()
|
||||
when you are done using the blkid library functions. This will save the
|
||||
cache to the blkid.tab file, if you have write access to the file. It
|
||||
will also free all associated devices and tags:
|
||||
|
||||
blkid_put_cache(cache);
|
Loading…
Reference in New Issue