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Chapter 9 Checking for Errors in LabWindows/CVI
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National Instruments Corporation 9-7 LabWindows/CVI Programmer Reference Manual
Formatting and I/O Library function that performed file I/O. The GetFmtIOErrorString
function converts this code into an error string. Refer to the LabWindows/CVI Standard
Library Reference Manual for more information.
Utility Library
Utility Library functions report error codes as return values. You can check each individual
function description in the LabWindows/CVI Standard Libraries Reference Manual or in the
LabWindows/CVI function panel help to determine the error conditions that can occur in each
function.
ANSI C Library
Some of the ANSI C library functions report error codes as return values. Some functions also
set the global variable
errno. Generally, the functions do not clear errno when they return
successfully. To learn more about these values, you can consult a publication such as C: A
Reference Manual cited in the Related Documentation section of About This Manual. Also,
you can use the LabWindows/CVI function panel help to determine the error conditions that
can occur in each function.
LabWindows/CVI Instrument Drivers
Instrument drivers from National Instruments use a standard status reporting scheme.
Functions report error codes as return values, and you can check each function individually
in the LabWindows/CVI function panel help to determine the error conditions that can occur
in each function.
Instrument drivers that comply with the VXIplug&play standard contain two error reporting
functions.
Prefix
_error_query, where
Prefix
is the instrument prefix, allows you to
query the error queue in the physical instrument. If the instrument does not have an error
queue,
Prefix
_error_query returns the VI_WARN_NSUP_ERROR_QUERY warning code
from the VISA Library.
Prefix
_error_message translates the error and warning codes
that the other instrument driver functions return into descriptive strings.
IVI instrument drivers are VXIplug&play compliant and so contain the
Prefix
_error_query and
Prefix
_error_message functions. In addition, IVI
instrument driver functions sometimes also provide a secondary error code or an elaboration
string to give you additional information about an error condition. You can use
Prefix
_GetErrorInfo to obtain the primary error code, secondary error code, and the
elaboration string for the first error that occurred on a particular instrument session or in the
current thread since you last called
Prefix
_GetErrorInfo. You also can use the
Prefix
_GetAttribute function to obtain each of these data items, individually, for the
most recent function call on a particular instrument session.
00ProRef.book : 06chap09.fm Page 7 Monday, March 9, 1998 3:23 PM