HI_Earliest

HI_Earliest — gives the earliest value in a history.

Syntax

#include <cogent.h>
ST_STATUS HI_Earliest(IP_hTASK  historian,
 char*  retbuf,
 int  buflen,
 char*  histname,
 HI_stVALUE*  data);

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.

histname

The name of a history.

data

The value and time of the first data item in the history.

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 returns the value for the first data item in the history. This item may be either in a file or in memory.

This function corresponds to the Cascade Historian earliest command and the hist_earliest dynamic library function.