Provided by: elektra-doc_0.7.1-1_all 
NAME
Key :: Meta Info Manipulation Methods -
Methods to do various operations on Key metainfo.
Functions
int keyStat (Key *key)
int keyRemove (Key *key)
uid_t keyGetUID (const Key *key)
int keySetUID (Key *key, uid_t uid)
gid_t keyGetGID (const Key *key)
int keySetGID (Key *key, gid_t gid)
int keySetDir (Key *key)
mode_t keyGetMode (const Key *key)
int keySetMode (Key *key, mode_t mode)
type_t keyGetType (const Key *key)
int keySetType (Key *key, type_t newType)
time_t keyGetATime (const Key *key)
int keySetATime (Key *key, time_t atime)
time_t keyGetMTime (const Key *key)
int keySetMTime (Key *key, time_t mtime)
time_t keyGetCTime (const Key *key)
int keySetCTime (Key *key, time_t ctime)
Detailed Description
Methods to do various operations on Key metainfo.
To use them:
#include <kdb.h>
Next to Name (key and owner) and Value (data and comment) there is the so called
metainfo inside every key.
Key metainfo insists of:
· UID, the user id
· GID, the group id
· filesystem-like mode permissions (rwx)
· Mode, change and modification times
The comment can contain userdata which directly belong to that key.
Owner is the user that owns the key. It only works for the user/ hierarchy.
Every user and group of your System has a uniqe ID. These values are used in the keys too.
They are very important for the mode. See man 2 chown.
With the mode mode you can choose if a user, group or the world can mode your key. See man
2 chmod.
Function Documentation
time_t keyGetATime (const Key *key) Get last time the key data was read from disk.
Every kdbGet() might update the access time of a key. You get information when the key was
read the last time from the database.
You will get 0 when the key was not read already.
Beware that multiple copies of keys with keyDup() might have different atimes because you
kdbGet() one, but not the other. You can use this information to decide which key is the
latest.
Parameters:
key Key to get information from.
Returns:
the time you got the key with kdbGet()
0 on key that was never kdbGet()
(time_t)-1 on NULL pointer
See also:
keySetATime()
kdbGet()
time_t keyGetCTime (const Key *key) Get last time the key metadata was changed from disk.
You will get 0 when the key was not read already.
Any changed field in metadata will influence the ctime of a key.
This time is not updated if only value or comment are changed.
Not changed keys will not update this time, even after kdbSet().
It is possible that other keys written to disc influence this time if the backend is not
grained enough.
Parameters:
key Key to get information from.
See also:
keySetCTime()
Returns:
(time_t)-1 on NULL pointer
the metadata change time
gid_t keyGetGID (const Key *key) Get the group ID of a key.
GID
The group ID is a unique identification for every group present on a system. Keys will
belong to root (0) as long as you did not get their real GID with kdbGet().
Unlike UID users might change their group. This makes it possible to share configuration
between some users.
A fresh key will have (gid_t)-1 also known as the group nogroup. It means that the key is
not related to a group ID at the moment.
Parameters:
key the key object to work with
Returns:
the system's GID of the key
(gid_t)-1 on NULL key or currently unknown ID
See also:
keySetGID(), keyGetUID()
mode_t keyGetMode (const Key *key) Return the key mode permissions.
Default is 0664 (octal) for keys and 0775 for directory keys which used keySetDir().
The defaults are defined with the macros KEY_DEF_MODE and KEY_DEF_DIR.
For more information about the mode permissions see Mode.
Parameters:
key the key object to work with
Returns:
mode permissions of the key
(mode_t)-1 on NULL pointer
See also:
keySetMode()
time_t keyGetMTime (const Key *key) Get last modification time of the key on disk.
You will get 0 when the key was not read already.
Everytime you change value or comment and kdbSet() the key the mtime will be updated. When
you kdbGet() the key, the atime is set appropriate.
Not changed keys may not even passed to kdbSet_backend() so it will not update this time,
even after kdbSet().
It is possible that other keys written to disc influence this time if the backend is not
grained enough.
If you add or remove a key the key thereunder in the hierarchy will update the mtime if
written with kdbSet() to disc.
Parameters:
key Key to get information from.
See also:
keySetMTime()
Returns:
the last modification time
(time_t)-1 on NULL pointer
type_t keyGetType (const Key *key) Returns the key data type.
See #type_t for the type definition.
See also:
keySetType()
keyIsBinary() and keyIsString()
keyIsDir() is not related to the type system
Parameters:
key key where to get the type.
Returns:
the key type
KEY_TYPE_UNDEFINED on keys without type
-1 on NULL pointer
uid_t keyGetUID (const Key *key) Get the user ID of a key.
UID
The user ID is a unique identification for every user present on a system. Keys will
belong to root (0) as long as you did not get their real UID with kdbGet().
Although usually the same, the UID of a key is not related to its owner.
A fresh key will have (uid_t)-1 also known as the user nobody. It means that the key is
not related to a user ID at the moment.
Parameters:
key the key object to work with
Returns:
the system's UID of the key
(uid_t)-1 on NULL key or currently unknown ID
See also:
keyGetGID(), keySetUID(), keyGetOwner()
int keyRemove (Key *key) Permanently remove a key after committing to database.
This functions sets a flag that the key needs to be removed. It also sets a flag that it
is not synced.
Remove the key instead of writing it in the key database when doing kdbSet() and related
functions.
This key will be ignored and it is save to delete it afterwards. To be sure that it was
removed, check if it needs sync with keyNeedSync().
Note:
Delete in elektra terminology means to free memory, remove means to free permanent
storage.
Warning:
You should not change a key's remove status once it belongs to a keyset. See ksSort()
for more information.
See also:
keyNeedRemove(), kdbSet(), kdbRemove()
Parameters:
key the key object to work with
Returns:
1 on success
-1 on NULL pointer
int keySetATime (Key *key, time_tatime) Update the atime information for a key.
When you do manual sync of keys you might also update the atime to make them
indistinguishable.
It can also be useful if you work with keys not using a keydatabase.
Parameters:
key The Key object to work with
atime The new access time for the key
Returns:
0 on success
-1 on NULL pointer
See also:
keyGetATime()
int keySetCTime (Key *key, time_tctime) Update the ctime information for a key.
Parameters:
key The Key object to work with
ctime The new change metadata time for the key
Returns:
0 on success
-1 on NULL pointer
See also:
keyGetCTime()
int keySetDir (Key *key) Set mode so that key will be recognized as directory.
The function will add all executable bits.
· Mode 0200 will be translated to 0311
· Mode 0400 will be translated to 0711
· Mode 0664 will be translated to 0775
The macro KEY_DEF_DIR (defined to 0111) will be used for that.
The executable bits show that child keys are allowed and listable. There is no way to have
child keys which are not listable for anyone, but it is possible to restrict listing the
keys to the owner only.
· Mode 0000 means that it is a key not read or writable to anyone.
· Mode 0111 means that it is a directory not read or writable to anyone. But it is
recognized as directory to anyone.
For more about mode see keySetMode().
It is not possible to access keys below a not executable key. If a key is not writeable
and executable kdbSet() will fail to access the keys below. If a key is not readable and
executable kdbGet() will fail to access the keys below.
Parameters:
key the key to set permissions to be recognized as directory.
Returns:
0 on success
-1 on NULL pointer
See also:
keySetMode()
int keySetGID (Key *key, gid_tgid) Set the group ID of a key.
See GID for more information about group IDs.
Parameters:
key the key object to work with
gid is the group ID
Returns:
0 on success
-1 on NULL key
See also:
keyGetGID(), keySetUID()
int keySetMode (Key *key, mode_tmode) Set the key mode permissions.
The mode consists of 9 individual bits for mode permissions. In the following explanation
the octal notation with leading zero will be used.
Default is 0664 (octal) for keys and 0775 for directory keys which used keySetDir().
The defaults are defined with the macros KEY_DEF_MODE and KEY_DEF_DIR.
Note:
libelektra 0.7.0 only allows 0775 (directory keys) and 0664 (other keys). More will be
added later in a sense of the description below.
Mode
0000 is the most restrictive mode. No user might read, write or execute the key.
Reading the key means to get the value and comment by kdbGet() or all highlevel methods.
Writing the key means to set the value and comment by kdbSet() or all highlevel methods.
Execute the key means to make a step deeper in the hierarchy. But you must be able to read
the key to be able to list the keys below. See also keySetDir() in that context. But you
must be able to write the key to be able to add or remove keys below.
0777 is the most relaxing mode. Every user is allowed to read, write and execute the key,
if he is allowed to execute and read all keys below.
0700 allows every action for the current user, identified by the uid. See keyGetUID() and
keySetUID().
To be more specific for the user the single bits can elect the mode for read, write and
execute. 0100 only allows executing which gives the information that it is a directory for
that user, but not accessible. 0200 only allows reading. This information may be combined
to 0300, which allows execute and reading of the directory. Last 0400 decides about the
writing permissions.
The same as above is also valid for the 2 other octal digits. 0070 decides about the group
permissions, in that case full access. Groups are identified by the gid. See keyGetGID()
and keySetGID(). In that example everyone with a different uid, but the gid of the the
key, has full access.
0007 decides about the world permissions. This is taken into account when neighter the uid
nor the gid matches. So that example would allow everyone with a different uid and gid of
that key gains full access.
Parameters:
key the key to set mode permissions
mode the mode permissions
Returns:
0 on success
-1 on NULL key
See also:
keyGetMode()
int keySetMTime (Key *key, time_tmtime) Update the mtime information for a key.
Parameters:
key The Key object to work with
mtime The new modification time for the key
Returns:
0 on success
See also:
keyGetMTime()
int keySetType (Key *key, type_tnewType) Set a new key type.
This method is usually not needed, unless you are working with more semantic value types,
or want to force a specific value type for a key. It is not usually needed because the
data type is automatically set when setting the key value.
See #type_t for the type defintion.
Example:
// here we define the new type
enum
{
KEY_TYPE_COLOR=KEY_TYPE_STRING+4
};
// here we make a new key with the type
Key *k1 = keyNew ('user/sw/oyranos/current/color1',
KEY_VALUE, '#4B52CA',
KEY_COMMENT, 'a custom color',
KEY_TYPE, KEY_TYPE_COLOR,
KEY_END);
// lets check if it is really correct type
if (keyGetType(k1) == KEY_TYPE_COLOR) printf ('correct type');
When using type_t::KEY_TYPE_DIR, this method will not set mode permissions to the key.
You'll have to set it manually after keySetType(), calling keySetMode() with appropriate
permissions. Or use the keySetDir().
See also:
keyGetType()
keySetDir() to see that the directory concept is independent of types
Parameters:
key the key object to work with
newType contains the new type
Returns:
0 on sucess
-1 on NULL pointer and when newType >= KEY_TYPE_MAX
int keySetUID (Key *key, uid_tuid) Set the user ID of a key.
See UID for more information about user IDs.
Parameters:
key the key object to work with
uid the user ID to set
Returns:
0 on success
-1 on NULL key
See also:
keySetGID(), keyGetUID(), keyGetOwner()
int keyStat (Key *key) Only stat a key instead of receiving value, comment and key type.
Only stat the key in the database when doing kdbGet(). The key may not have any value,
comment or key type set.
It is not possible to revert the action on per-key basis. When you want to remove the flag
you have to pass option_t::KDB_O_NOSTAT to the next kdbGet().
See also:
keyNeedStat(), kdbGet()
Parameters:
key the key object to work with
Returns:
1 on succuess
-1 on NULL pointer
Author
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