Cascade Historian: Version 4.1
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# register

register -- registers histories with the Cascade DataHub.

## Syntax

    (register pattern)

## Parameters

`pattern`

  The name of one or more (using a globbing pattern) histories previously defined by the history command. When this parameter is not specified, the default is `*`, to include all histories.

## Returns

`t` (true) if successful, otherwise

        (error "No history matching pattern")

## Description

This command causes the Cascade Historian to register each history matching the pattern with the Cascade DataHub point of the same name. Any subsequent value changes transmitted by the Cascade DataHub will be treated exactly the same as if add or `HI_Add` were called with that history, value and timestamp. If a history has already been registered, this function does nothing. If the Cascade DataHub is not running, no registration occurs. If multiple histories are associated with the same point, registering or unregistering one of the histories will do the same to all the other histories sharing the same point.

A Cascade DataHub point is a unit of storage in the datahub. Points have a name (a string), a value (real, integer, or string), and a time associated with them. They can be written to the Cascade DataHub in a number of ways, including for example the Cascade DataHub writept command and the Gamma `write_point` function. The Cascade Historian receives a point's data from the Cascade DataHub by registering for it with the register command or `HI_Register` function.

This command corresponds to the Cogent API function `HI_Register` and the `hist_register` dynamic library function.

## Example

        (register p1)
        (register p*)

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