2.8 - Debugging Functions
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2.8 - Debugging Functions

Debugging Functions Overview

LJM contains debug logging functionality that is disabled by default.

Once enabled, LJM will write messages to the LJM debug log file. These messages can contain error messages, warnings, raw packets, and other information.

LJM's debug logging can be enabled using one of two methods – via ljm_startup_configs.json or via LJM_WriteLibraryConfigS. Both methods (described below) require changing the following LJM configuration parameters:

  • Change LJM_DEBUG_LOG_MODE to LJM_DEBUG_LOG_MODE_CONTINUOUS (equal to 2).
  • Change LJM_DEBUG_LOG_LEVEL to one of the possible debug levels. Use LJM_STREAM_PACKET (equal to 1) if you want to ensure that all debug messages are output.
  • Change LJM_DEBUG_LOG_FILE_MAX_SIZE to a large number like 123456789 if your program will be running for a long time.

Enabling via ljm_startup_configs.json

The file ljm_startup_configs.json contains the LJM configurations that are used by LJM when LJM is loaded.

Note that ljm_startup_configs.json is installed / replaced every time the LJM installer is run, so this method is temporary. LJM installs ljm_startup_configs.json to the following locations:

  • Windows Vista and later - C:\ProgramData\LabJack\LJM\ljm_startup_configs.json
  • Windows XP (deprecated) - C:\Documents and Settings\All Users\Application Data\LabJack\LJM\ljm_startup_configs.json
  • Mac OS X and Linux - /usr/local/share/LabJack/LJM/ljm_startup_configs.json

After opening ljm_startup_configs.json with a text editor, change the parameters as described above.

Enabling via LJM_WriteLibraryConfigS

Use the function LJM_WriteLibraryConfigS to change the LJM parameters as described above.

2.8.1 - Log

Saves a message of the specified severity level to the LJM debug log file.

Syntax

LJM_ERROR_RETURN LJM_Log(
                      int Level, 
                      const char * String)

Parameters

Level [in]
The error severity level of this new log entry. See constants file LJM_DEBUG_LOG_LEVEL.
  • LJM_STREAM_PACKET = 1
  • LJM_TRACE = 2
  • LJM_DEBUG = 4
  • LJM_INFO = 6
  • LJM_PACKET = 7
  • LJM_WARNING = 8
  • LJM_USER = 9
  • LJM_ERROR = 10
  • LJM_FATAL = 12
String [in]
The debug message to write to the log file.

Returns

LJM errorcodes or 0 for no error.

Remarks

By default, LJM_DEBUG_LOG_MODE is to never log, so LJM does not output any log messages, even from this function. Users must first use LJM_WriteLibraryConfigS to change the log mode. See the library configuration functions.

Examples

[C/C++] Write "Beginning stream..." to the log file with severity level: Debug.

int LJMError;
LJMError = LJM_Log(4, "Beginning stream...");

2.8.2 - ResetLog

Clears all characters from the debug log file.

Syntax

LJM_ERROR_RETURN LJM_ResetLog()

Parameters

None.

Returns

LJM errorcodes or 0 for no error.

Remarks

See the LJM configuration properties for Log-related properties.

Examples

[C/C++] Clear the log file.

int LJMError;
LJMError = LJM_ResetLog();