Provides the date and time of the first (oldest) available measurement value from a HistoryBase ring buffer.
Syntax
HistoryBaseFirstTime(HistoryBaseFile, [ TraceGroup = "" ] [ , Machine = "" ])
The syntax of the HistoryBaseFirstTime function consists of the following parts:
Part |
Description |
|---|---|
HistoryBaseFile |
String with the path of the ring buffer file to be read. Permitted data structures are Scalar value. Supported data types are String (file name). |
TraceGroup |
Name of the trace group whose time trace is to be used as a basis. If the group is not specified, the first time of all groups will be returned. Permitted data structures are Scalar value. Supported data types are String. If this argument is omitted, it will be set to the default value "" . |
Machine |
Name of a computer in the network on which the specified ring buffer file is already being used by a HistoryBase component. This argument can also be an empty text. In this case, the HistoryBase instance of the ring buffer will be searched or, if necessary, instantiated on the executing machine. Permitted data structures are Scalar value. Supported data types are String. If this argument is omitted, it will be set to the default value "" . |
Remarks
The result always has the data structure Scalar value.
Weisang HistoryBase version 4 or higher has to be installed on the executing system and, if applicable, on the system specified by Machine. If data is currently being written to the ring buffer, the function uses a security buffer to ensure that the returned time value can be safely used as a starting time for a following execution of the HistoryBaseRead and HistoryBaseReadTime functions.
If an argument is a list, then the first element in the list is taken. If this is also a list, then the process is repeated.
Available in
FlexPro View, Basic, Professional, Developer Suite
Examples
HistoryBaseFirstTime("C:\HistoryBase.hbf", "RemoteMachine") |