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The registry package provides a general set of operations for manipulating the Windows registry. The package implements the registry Tcl command. This command is only supported on the Windows platform. Warning: this command should be used with caution as a corrupted registry can leave your system in an unusable state.

KeyName is the name of a registry key. Registry keys must be one of the following forms:

\\hostname\rootname\keypath

rootname\keypath

rootname

Hostname specifies the name of any valid Windows host that exports its registry. The rootname component must be one of HKEY_LOCAL_MACHINE, HKEY_USERS, HKEY_CLASSES_ROOT, HKEY_CURRENT_USER, HKEY_CURRENT_CONFIG, HKEY_PERFORMANCE_DATA, or HKEY_DYN_DATA. The keypath can be one or more registry key names separated by backslash (\) characters.

The optional -mode argument indicates which registry to work with; when it is -32bit the 32-bit registry will be used, and when it is -64bit the 64-bit registry will be used. If this argument is omitted, the system's default registry will be the subject of the requested operation.

Option indicates what to do with the registry key name. Any unique abbreviation for option is acceptable. The valid options are:

registry broadcast keyName ?-timeout milliseconds?

Sends a broadcast message to the system and running programs to notify them of certain updates. This is necessary to propagate changes to key registry keys like Environment. The timeout specifies the amount of time, in milliseconds, to wait for applications to respond to the broadcast message. It defaults to 3000. The following example demonstrates how to add a path to the global Environment and notify applications of the change without requiring a logoff/logon step (assumes admin privileges):

set regPath [join {
    HKEY_LOCAL_MACHINE
    SYSTEM
    CurrentControlSet
    Control
    {Session Manager}
    Environment
} "\\"]
set curPath [registry get $regPath "Path"]
registry set $regPath "Path" "$curPath;$addPath"
registry broadcast "Environment"

registry delete keyName ?valueName?

If the optional valueName argument is present, the specified value under keyName will be deleted from the registry. If the optional valueName is omitted, the specified key and any subkeys or values beneath it in the registry hierarchy will be deleted. If the key could not be deleted then an error is generated. If the key did not exist, the command has no effect.

registry get keyName valueName

Returns the data associated with the value valueName under the key keyName. If either the key or the value does not exist, then an error is generated. For more details on the format of the returned data, see SUPPORTED TYPES, below.

registry keys keyName ?pattern?

If pattern is not specified, returns a list of names of all the subkeys of keyName. If pattern is specified, only those names matching pattern are returned. Matching is determined using the same rules as for string match. If the specified keyName does not exist, then an error is generated.

registry set keyName ?valueName data ?type??

If valueName is not specified, creates the key keyName if it does not already exist. If valueName is specified, creates the key keyName and value valueName if necessary. The contents of valueName are set to data with the type indicated by type. If type is not specified, the type sz is assumed. For more details on the data and type arguments, see SUPPORTED TYPES below.

registry type keyName valueName

Returns the type of the value valueName in the key keyName. For more information on the possible types, see SUPPORTED TYPES, below.

registry values keyName ?pattern?

If pattern is not specified, returns a list of names of all the values of keyName. If pattern is specified, only those names matching pattern are returned. Matching is determined using the same rules as for string match.

Supported types

Each value under a key in the registry contains some data of a particular type in a type-specific representation. The registry command converts between this internal representation and one that can be manipulated by Tcl scripts. In most cases, the data is simply returned as a Tcl string. The type indicates the intended use for the data, but does not actually change the representation. For some types, the registry command returns the data in a different form to make it easier to manipulate. The following types are recognized by the registry command:

binary: The registry value contains arbitrary binary data. The data is represented exactly in Tcl, including any embedded nulls.
none: The registry value contains arbitrary binary data with no defined type. The data is represented exactly in Tcl, including any embedded nulls.
sz: The registry value contains a null-terminated string. The data is represented in Tcl as a string.
expand_sz: The registry value contains a null-terminated string that contains unexpanded references to environment variables in the normal Windows style (for example, “%PATH%”). The data is represented in Tcl as a string.
dword: The registry value contains a little-endian 32-bit number. The data is represented in Tcl as a decimal string.
dword_big_endian: The registry value contains a big-endian 32-bit number. The data is represented in Tcl as a decimal string.
link: The registry value contains a symbolic link. The data is represented exactly in Tcl, including any embedded nulls.
multi_sz: The registry value contains an array of null-terminated strings. The data is represented in Tcl as a list of strings.
resource_list: The registry value contains a device-driver resource list. The data is represented exactly in Tcl, including any embedded nulls.

In addition to the symbolically named types listed above, unknown types are identified using a 32-bit integer that corresponds to the type code returned by the system interfaces. In this case, the data is represented exactly in Tcl, including any embedded nulls.

Portability issues

The registry command is only available on Windows.

Example

Print out how double-clicking on a Tcl script file will invoke a Tcl interpreter:

package require registry
set ext .tcl

# Read the type name
set type [registry get HKEY_CLASSES_ROOT\\$ext {}]
# Work out where to look for the command
set path HKEY_CLASSES_ROOT\\$type\\Shell\\Open\\command
# Read the command!
set command [registry get $path {}]

puts "$ext opens with $command"

Licensed under Tcl/Tk terms
https://www.tcl.tk/man/tcl/TclCmd/registry.htm