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, or HKEY_CURRENT_CONFIG. The keypath can be one or more registry key names separated by backslash (\e) characters.

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

• 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 heirarchy 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 isn't 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 isn't specified, creates the key keyName if it doesn't 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 isn't 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 isn't 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.

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. Tcl
• 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.

The registry command is only available on Windows.