$SYSTEM
Synopsis
$SYSTEM $SY $SYSTEM.class.method()
Description
$SYSTEM can be invoked as either a special variable or as a class which invokes methods that return system information.
$SYSTEM Special Variable
$SYSTEM as a special variable contains the local system name and the name of the current instance of Caché, separated by a colon (:). The name of the machine follows the case conventions of the local operating system and the name of the instance is in uppercase. If Caché is part of the name of the instance, there is no accent on the final letter. For example:
MyComputer:CACHE2
You can also determine your local system name using the LocalHostName()Opens in a new tab method:
WRITE $SYSTEM,!
WRITE $SYSTEM.INetInfo.LocalHostName() The abbreviation $SY can only be used for $SYSTEM as a special variable.
$SYSTEM Class
$SYSTEM as a class provides access to a variety of system objects. You can invoke a method that returns information, or a method that performs some operation such as upgrading or loading and returns status information. Caché supports several classes of system objects, including the following:
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Version: for version numbers of Caché and its components
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SYS: for the system itself
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OBJ: for Objects
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SQL: for SQL queries
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CSP: for Caché Server Pages
Note that object class names and method names are case-sensitive. Specifying the wrong case for these names results in a <CLASS DOES NOT EXIST> or <METHOD DOES NOT EXIST> error. If you do not specify parentheses with the method name, it issues a <SYNTAX> error.
$SYSTEM methods and properties can be accessed using dot syntax, as shown in the following equivalent syntax examples:
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WRITE ##class(%SYSTEM.INetInfo).LocalHostName()
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WRITE $SYSTEM.INetInfo.LocalHostName()
$SYSTEM can access the System API classes in the %SYSTEM class package, described in the InterSystems Class Reference documentation. Note that in the ##class syntax the %SYSTEM class package name is case-sensitive. In the $SYSTEM syntax the $SYSTEM keyword is not case-sensitive. For further information on using dot syntax, refer to the chapter “Working with Registered Objects” in Defining and Using Classes.
For further information on using %SYSTEM.OBJOpens in a new tab, refer to Flags and Qualifiers.
Flags and Qualifiers
These are arguments which can be used to control the import of external sources into Caché, compile existing applications, and export these to external destinations. In the class documentation for %SYSTEM.OBJOpens in a new tab, these are often supplied as the value of the parameter, qspec. The available settings for each can be displayed by the commands:
DO $SYSTEM.OBJ.ShowFlags()and
DO $SYSTEM.OBJ.ShowQualifiers()Flags
Of the two, the flags are the earlier. They were modeled on UNIX® command-line parameters and thus are one- or two-character sequences. The existing flags and their meanings (excluding deprecated flags) are:
| Flag | Meaning | Default |
|---|---|---|
| b | Includes subclasses and classes that reference the current class in SQL usage. | |
| c | Compiles the class definitions after loading. | |
| d | Display. Flag set by default. | X |
| e | Deletes the extent definition that describes the global storage used by the extent, and deletes the data. | |
| h | Shows hidden classes. | |
| i | Validates XML export format against schema on Load. Flag set by default. | X |
| k | Keep source. When this flag is set, source code of generated routines will be kept. | |
| l | Locks classes while compiling. Flag set by default. | X |
| p | Includes classes whose names begin with the “%” character. | |
| r | Recursive. Compiles all the classes that are dependency predecessors. | |
| s | System. Processes system messages or application messages. | |
| y | Includes classes that are related to the current class; classes that either reference the current class in SQL usage, or are referenced by the current class in SQL usage. | |
| o1, o2, o3, o4 | Optimization specifiers. Deprecated and ignored by the class compiler. |
Flags may be turned off by preceding them with a dash (-).
Qualifiers
During the development of Caché version 5.1, it became clear that flags would be insufficient to provide for the emerging needs of import, export and compilation. Rather than replace the flags mechanism, a newer, more extensible set of controls was implemented: qualifiers. To preserve backward compatibility, the flag mechanism remains fully supported. In addition, a qualifier exists whose meaning is the same as each existing flag, and the two may be used in the same specifier.
Since there are so many more qualifiers, they are organized into groups according to the function they control as shown in the following tables. Deprecated qualifiers are not shown.
You can also set these qualifiers for the current namespace (the default) or system-wide using the SetQualifiers()Opens in a new tab method.
| Flag | Meaning | Default |
|---|---|---|
| /autoinclude | Automatically includes any classes that are not up to date that are required to compile this class. | 1 |
| /checkschema | Validates imported XML files against the schema definition. | 1 |
| /checksysutd | Checks system classes for up-to-dateness. | 0 |
| /checkuptodate | Skips classes or expanded classes that are up-to-date. | expandedonly |
| /compile | Causes classes loaded to be compiled as well. | 0 |
| /cspcompileclass | Causes classes created by CSP or CSR load to be compiled. | 1 |
| /cspdeployclass | When CSP page loaded deploys the class generated. | 0 |
| /csphidden | Classes generated from CSP and CSR compilation are marked as hidden. | 1 |
| /defaultowner | When loading classes, if the Owner keyword is not defined, insert the user name specified in this string into the class definition as the class owner. If the value of this string is $USERNAME, insert the current user name into the class definition as the class owner. | — |
| /defines | Comma separated list of macros to define and, optionally, their values. | — |
| /deleteextent | Deletes the extent definition that describes the global storage used by the extent, and deletes the data. | 0 |
| /diffexport | Does not include any time or platform information in export so the files can be run through diff/merge tools. | 0 |
| /display | Alias qualifier for /displaylog and /displayerror. | — |
| /displayerror | Displays error information. | 1 |
| /displaylog | Displays log information. | 1 |
| /expand | Alias qualifier for /predecessorclasses, /subclasses and /relatedclasses. | — |
| /exportgenerated | When exporting classes also exports generated classes where the class generating them is also included. | 0 |
| /exportselectivity | Exports the selectivity values stored in the storage definition for this class. | 1 |
| /filterin | Alias qualifier for /application, /system and /percent. | — |
| /generated | Determines when expanding patterns or lists of classes in a package whether to include generated items (routines, classes, etc.). | 1 |
| /generatemap | Generates the map file. | 1 |
| /importselectivity | 0: Do not import selectivity values from the XML file. 1: Import the selectivity values stored in the storage definition when importing XML file. 2: Keep the existing class selectivity values, but if the existing class does not have selectivity specified for something that is present in the XML file then use the selectivity value from the XML file. | 2 |
| /includesubpackages | Includes sub-packages. | 1 |
| /journal | Journaling enabled while performing a class compile. If the process performing the compile has specifically disabled journaling, /journal defaults to 0, rather than the system-wide default of 1. | 1 |
| /keepsource | Keeps the source code of generated routines. | 0 |
| /lock | Uses LOCK command while compiling classes. | 1 |
| /mapped | Includes classes mapped from another database. If you specifically ask to compile a class from another database (CompileList() method), the class will be compiled regardless of the /mapped setting. /mapped only applies when the code is searching for classes, for example, using the CompileAll() method. | 0 |
| /mergeglobal | If importing a global from XML file merges the global with existing data. | 0 |
| /multicompile | Enables multiple users’ jobs to compile classes. | 1 |
| /percent | Includes percent classes. | 0 |
| /predecessorclasses | Recursively includes dependency predecessor classes. | 0 |
| /relatedclasses | Recursively includes related classes. | 0 |
| /retainstorage | When a class is compiled, the compiler generates a storage definition. By default, if the storage definition is updated the class definition is updated with the updated storage definition. If a new version of the class is loaded from an external source, that updated storage definition is overwritten by whatever is defined in the new version of the class definition. If the new version of the class does not include a storage definition then the existing storage definition is removed. Setting /retainstorage saves the existing storage definition temporarily and restores it after the new version of a class is loaded. If the new version of the class also defines the storage definition, the existing storage definition is overwritten and not retained. If the new version of the class does not define the storage definition, the previous version of the storage definition is restored. | 0 |
| /subclasses | Recursively includes sub-classes. | 0 |
| /system | Processes system messages or application messages. | 0 |
| Flag | Meaning | Default |
|---|---|---|
| /checksysutd | Checks system classes for up-to-dateness. | 0 |
| /checkuptodate | Checks if classes are up-to-date when projecting. | expandedonly |
| /createdirs | Creates directories if they do not exist. | 0 |
| /cspdeployclass | When CSP page loaded deploys the class generated. | 0 |
| /diffexport | Does not include any time or platform information in export so the files can be run through diff/merge tools. | 0 |
| /display | Alias qualifier for /displaylog and /displayerror. | — |
| /displayerror | Displays error information. | 1 |
| /displaylog | Displays log information. | 1 |
| /documatichost | Host that is used in JavaDoc generation. | — |
| /documaticnamespace | Namespace that is used in JavaDoc generation. | — |
| /documaticport | Port that is used in JavaDoc generation. | — |
| /exportgenerated | When exporting classes also exports generated classes where the class generating them is also included. | 0 |
| /exportselectivity | Exports the selectivity values stored in the storage definition for this class. | 1 |
| /exportversion | Specifies the target Caché version to load this export as a three-part release version, for example 2012.2.2. Cache uses the /exportversion value to handle changes in the export format across versions of Caché by removing class keywords that were not implemented in the earlier Caché version. Specifying /exportversion does not guarantee compatibility of code between the exporting and importing systems. | The current version of Caché |
| /generatemap | Generates the map file. | 1 |
| /generationtype | Generation mode. | — |
| /genserialuid | Generates serialVersionUID. | 1 |
| /importselectivity | 0: do not import selectivity values from the XML file; 1: import the selectivity values stored in the storage definition when importing XML file; 2: keep any existing selectivity values but if a property does not have an existing value then use the selectivity from the XML file. | 2 |
| /includesubpackages | Includes sub-packages. | 1 |
| /javadoc | Does not create javadoc. | 1 |
| /make | Only generates dependency or class if timestamp of last compilation is greater than timestamp of last generation. | 0 |
| /mapped | Includes classes mapped from another database. | 0 |
| /mergeglobal | If importing a global from XML file merges the global with existing data. | 0 |
| /newcollections | Uses native Java collections. | 1 |
| /percent | Includes percent classes. | 0 |
| /pojo | POJO generation mode. | 0 |
| /predecessorclasses | Recursively includes dependency predecessor classes. | 0 |
| /primitivedatatypes | Uses Java primitives for %Integer, %Boolean, %BigInt, %Decimal. | 0 |
| /projectabstractstream | Projects classes that contain methods whose arguments are abstract streams or whose return type is an abstract stream. | 0 |
| /projectbyrefmethodstopojo | Projects byref methods to pojo implementation. | 0 |
| /recursive | Exports classes recursively. | 1 |
| /relatedclasses | Recursively includes related classes. | 0 |
| /skipstorage | Does not export the class storage information. | 0 |
| /subclasses | Recursively includes sub-classes. | 0 |
| /system | Processes system messages or application messages. | 0 |
| /unconditionallyproject | Projects regardless of problems that may prevent code from compiling or working correctly. | 0 |
| /usedeepestbase | Uses deepest base in which method or property is defined for method or property definition. If P is defined in A,B, and C and A extends B extends C, then C is a deeper base for P. | 0 |
| Flag | Meaning | Default |
|---|---|---|
| /detail | Shows detailed information. | 0 |
| /diffexport | Does not include any time or platform information in export so the files can be run through diff/merge tools. | 0 |
| /hidden | Shows hidden classes. | 0 |
| /system | Processes system messages or application messages. | 0 |
| Flag | Meaning | Default |
|---|---|---|
| /autoload | Specifies the directory to be auto-loaded. | — |
| /cleanup | Cleans up globals upon completion of unit test. By default, globals are not cleaned up. Even when set, DeepSee globals are not cleaned up. | 0 |
| /debug | Causes the Asserts to BREAK if they fail. | 0 |
| /delete | Determines if loaded classes should be deleted. | 1 |
| /display | Alias qualifier for /displaylog and /displayerror. | — |
| /displayerror | Displays error information. | 1 |
| /displaylog | Displays log information. | 1 |
| /findleakedvariables | When enabled, the public variables currently set in the process are recorded before a test is run, then compared with those set after the test is completed. Other than a predetermined set of known context and output variables, such as SQLCODE, any newly defined variables are reported, with their values, as a test failure. | 0 |
| /load | Determines if classes should be loaded; if not, then only classnames are obtained from the directories. | 1 |
| /loadudl | Loads UDL files produced by Atelier. When set, loads .cls, .mac, .int, and .inc files. /loadudl and /loadxml can be used to limit what types of files are loaded; by default, all files are loaded. UDL files are always loaded as UTF8 so that Unicode characters are loaded correctly. | 1 |
| /loadxml | Loads XML files produced by Studio. When set, loads .xml files. /loadudl and /loadxml can be used to limit what types of files are loaded; by default, all files are loaded. | 1 |
| /recursive | Determines if tests in subdirectories should run recursively. | 1 |
| /run | Determines if tests should run. | 1 |
These qualifiers are given in the qspec as they appear, for example, “/compile/displayerror/subclasses”. No spaces are allowed between qualifiers.
Qualifiers may be negated by preceding the qualifier with “no” as in “/nodisplaylog”. Alternatively, the value of the qualifier can be specified explicitly as in “/displaylog=0”.
Qualifiers For Flags
The following table gives the existing flag and the equivalent qualifier. Some flags map into multiple qualifiers, and also have different meanings when used for differing purposes.
| Flag | Group | Qualifier | Default |
|---|---|---|---|
| b | Compiler | /subclasses | 0 |
| c | Compiler | /compile | 0 |
| d | Compiler | /displayerror | 1 |
| d | Compiler | /displaylog | 1 |
| d | UnitTest | /displayerror | 1 |
| d | UnitTest | /displaylog | 1 |
| e | Compiler | /deleteextent | 0 |
| i | Compiler | /checkschema | 1 |
| k | Compiler | /keepsource | 0 |
| l | Compiler | /lock | 1 |
| p | Compiler | /percent | 0 |
| r | Compiler | /predecessorclasses | 0 |
| r | Compiler | /includesubpackages | 1 |
| s | Compiler | /system | 0 |
| y | Compiler | /relatedclasses | 0 |
| b | Export | /subclasses | 0 |
| d | Export | /displayerror | 1 |
| d | Export | /displaylog | 1 |
| g | Export | /exportselectivity | 0 |
| p | Export | /percent | 0 |
| r | Export | /includesubpackages | 1 |
| r | Export | /recursive | 1 |
| r | Export | /predecessorclasses | 0 |
| s | Export | /system | 0 |
| y | Export | /relatedclasses | 0 |
| h | ShowClassAndObject | /hidden | 0 |
| s | ShowClassAndObject | /system | 0 |
Order Of Processing
The qspec is processed from left to right. The setting for a given flag or qualifier overrides the current setting whether it came from the environment defaults, or from an occurrence earlier in the qspec.
When both flags and qualifiers appear, the flags must be placed before (to the left of) the qualifiers. This means that qualifier settings always override any flag settings.
Examples
The following is an example of using $SYSTEM to invoke a method that returns system information:
WRITE $SYSTEM.OBJ.Version()returns a string such as the following:
Cache Objects Version 2017.2.0.307
Note that this objects version is not formatted the same as the system version number contained in the $ZVERSION special variable.
You can list all of the methods for the OBJ class as follows. (By changing the class name, you can use this method to get a list for any system class):
DO $SYSTEM.OBJ.Help()To list information about just one method in a class, specify the method name in the Help argument list, as shown in the following example:
DO $SYSTEM.OBJ.Help("Load")The following are a few more examples of $SYSTEM that invoke methods:
DO $SYSTEM.OBJ.Upgrade()
WRITE !,"* * * * * * * * * * * "
DO $SYSTEM.CSP.DisplayConfig()
WRITE !,"* * * * * * * * * * * "
WRITE !,$SYSTEM.Version.GetPlatform()
WRITE !,"* * * * * * * * * * * "
WRITE !,$SYSTEM.SYS.TimeStamp()The following example calls the same methods as the previous example, using the ##class(%SYSTEM) syntax form:
DO ##class(%SYSTEM.OBJ).Upgrade()
DO ##class(%SYSTEM.CSP).DisplayConfig()
WRITE !,##class(%SYSTEM.Version).GetPlatform()
WRITE !,##class(%SYSTEM.SYS).TimeStamp()The previous two examples requires that UnknownUser have assigned the %DB_CACHESYS role.
See Also
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$ISOBJECT function
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$ZVERSION special variable
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Working with Registered Objects in Using Caché Objects
