HI_Unregister

Cogent API and Utilities: Version 4.1
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# `HI_Unregister`

`HI_Unregister` -- unregisters histories with the Cascade DataHub.

## Syntax

    #include <cogent/cogent.h>

``ST_STATUS HI_Unregister`(IP_hTASK historian, char* retbuf, int buflen, char* histpattern);`

## Arguments

`historian`

  The task pointer to the Cascade Historian program.

`retbuf`

  An optional buffer containing an error message.

`buflen`

  The length in bytes of `retbuf`. If `retbuf` is non-NULL, this must be a valid non-zero length. If `retbuf` is NULL, this parameter is ignored.

`histpattern`

  A globbing pattern specifying a group of histories.

## Returns

`ST_OK` on success. Otherwise `ST_ERROR`, and the `retbuf` will contain a NULL-terminated character string with an error message. If the return value is `ST_OK`, the `retbuf` may not contain useful information.

## Description

This function causes the Cascade Historian to unregister each history matching the pattern from the Cascade DataHub. The history will cease to receive exceptions when the point value data changes. 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.

If the history is not currently registered with the Cascade DataHub, this function does nothing.

This function corresponds to the Cascade Historian unregister command and the `hist_unregister` dynamic library function.

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