National Instruments 320685D-01 ユーザーズマニュアル

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 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.

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.

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.

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