An S-language interface to the Windows Registry
This package provides a basic interface to the Windows registry.
There are S functions and C routines for basic investigation of the
contents of the registry, allowing one to find out the names of the
sub-keys and the names of the keys that contain actual values. It
also allows one, of course, to retrieve the value of a particular key
and to set the value of a key, including create a new one.
There are numerous facilities that we could add from the Windows API,
but have not done so -- yet! Please ask if you need more
functionality added. Ideally, please send some code that implements
it also and I will add it to the package so that there is a single
package which has all the functionality.
Get the names of the Sub-Keys
If one uses the Regedit tool, you can see that there are several
primary keys under the root key
My Computer. These are the
builtin keys and are also available in R in the variable
.BuiltinKeys. Notice that each of these has
a + beside it, indicating that there are sub-keys which you can
explore if you click on that key. For instance, if you select
HKEY_LOCAL_MACHINE you'll see 5 other keys under that named
HARDWARE,
SAM,
SECURITY,
SOFTWARE and
SYSTEM. (This is on my Windows
2000 machine. Your's may differ slightly.) All of these except
SECURITY has sub-keys. If we select
SOFTWARE,
we get a reasonably length list of different pieces of software
installed on this machine. Some of these have sub-keys, and some do
not. Since I have Perl installed, it appears in this list and it has
no sub-keys. It does however have a value within this key,
specifically
BinDir. This tells us where on the system the
Perl executable is located; a useful thing to know. We can get the
values of the keys within a "key folder" using the S function
getRegistryKeyValues.
getRegistryKeyValues("SOFTWARE\\Perl", top = "HKEY_LOCAL_MACHINE")
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Note that we give the top-level key via the argument
top and then specify the path to the collection of
values as "SOFTWARE" and then "Perl". We separate the elements in
this path using \ which we must specify as \\ in R.
Rather than explicitly specifying the name of the top-level
key, we can specify the index in the .BuiltinKeys
vector.
getRegistryKeyValues("SOFTWARE\\Perl", top = 4)
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Alternatively, we can use a short-hand version by allowing
partial matching to find the relevant index.
getRegistryKeyValues("SOFTWARE\\Perl", top = "HKEY_LOC")
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In the near future, we will also allow
a single path
getRegistryKeyValues("HKEY_LOCAL_MACHINE\\SOFTWARE\\Perl")
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What this returns us is a named list. The names are the keys. The
elements are the values in the registry converted as appropriate.
Strings are converted to S strings, DWORD values are converted to
integers (currently).
Note
We'll add more facilities for this soon.
But what if we didn't have Regedit? How would find out the names of
the sub-keys within a key? We can always call
getRegistryKeyValues but this only identifies
keys that actually have values. It omits sub-keys that have sub-keys,
i.e. key folders. To find these, we can use the function
getRegistrySubKeyNames.
getRegistrySubKeyNames("SOFTWARE", 4)
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> getRegistrySubKeyNames(c("Control Panel", "Desktop"), top = 3)
[1] "WindowMetrics"
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Note from this example that we can also specify the
elements or terms in a path as separate elements
of a character vector as opposed to
separating them with \\\\.
The function
setRegistryValue allows one to
set a value within the registry. One specifies the path to the key
folder and the name of the key within that folder to identify the
specific key to be set. Then one sets
Identifying nodes and paths
This package offers a variety of different ways to specify a path in
the registry to identify a node or key.
.resolveToplevelRegistryKey(.BuiltinKeys[1], "Control Panel")
.resolveToplevelRegistryKey(.BuiltinKeys[1], "Control Panel\\Panel")
.resolveToplevelRegistryKey(.BuiltinKeys[1], "HKEY_CLASSES_ROOT\\Control Panel\\Panel")
.resolveToplevelRegistryKey(.BuiltinKeys[1], c("HKEY_CLASSES_ROOT", "Control Panel", "Panel"))
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