niRFSA_GetAttributeViString

ViStatus = niRFSA_GetAttributeViString (ViSession vi, ViConstString channelName, ViAttr attributeId, ViString *value);

Purpose

Queries the value of a ViString attribute.

You can use this low-level function to get the values of inherent IVI attributes, class-defined attributes, and instrument-specific attributes. If the attribute represents an instrument state, this function performs instrument I/O in the following cases:

• State caching is disabled for the entire session or for the particular attribute.
• State caching is enabled, and the currently cached value is invalid.

You must provide a ViString (ViChar array) to serve as a buffer for the value. You pass the number of bytes in the buffer as the bufferSize parameter. If the current value of the attribute, including the terminating NULL byte, is larger than the size you indicate in the bufferSize parameter, the function copies buffer size minus 1  bytes into the buffer, places an ASCII NULL byte at the end of the buffer, and returns the buffer size you must pass to get the entire value. For example, if the value is "123456" and the buffer size is 4, the function places "123" into the buffer and returns 7.

If you want to call this function just to get the required buffer size, you can pass 0 for the bufferSize and VI_NULL for the attributeValue buffer.

If you want the function to fill in the buffer regardless of the number of bytes in the value, pass a negative number for the buffer size parameter.

Parameters

Return Value