Log4mql(mini) - light header-only version of Log4mql that provides standardized logging.

Installation/Usage

• Add log4mqlm.mqh to your Include folder.
• View the sample code to get an overview of the usage.

Inputs

Log4mql(mini) requires only one input field. There is no logging to files.

• Loglevel, supports Trace, Debug, Info, Warn, Error and Fatal

Message Pattern

The message pattern will have a fixed format which corresponds to its appropriate severity level, according to below table.

Severity	Format	Sample output
Info (the commonly used default)	%func: %msg	OnInit:  Log level: TRACE
Debug, Trace	%func(%file:%line): %msg	OnInit(log4mqlm_sample.mq5:72): initializing
Warn	WARN %func(%file:%line): %msg	WARN SomeFunction(log4mqlm_sample.mq5:64): stoploss too tight
Error	ERROR %func(%file:%line): %msg optionally followed by: [, error %lasterr - %lasterrdesc]	ERROR OnDeinit(log4mqlm_sample.mq5:85): open 'some file' failed,  error 5004 - Cannot open file
Fatal	FATAL ... as above	FATAL  ...

Functions

Log4mql(mini) provides functions and preprocessor macros for logging, all macros are to be used like functions.

Return type	Function name	Description
bool	PRINT (...)	Prints its message if log level is set at least to INFO (= normal logging behavior).  Supports up to 9 arguments - PRINT("1",2,etc) - if you need more, expand the templates.  Returns true if message was logged, else false.
bool	PRINTF (string format,...)	Like PRINT but prints a formatted message. Same rules as known from PrintFormat apply.
bool	WARN (...)  WARNF (string format,...)	Prints its message if log level is set at least to WARN.
bool	ERROR (...)  ERRORF (string format,...)	Prints its message if log level is at least ERROR. Adds _LastError description if set.
bool	FATAL (...)  FATALF (string format,...)	Like ERROR, but with termination. You should call ExpertRemove() or exit immediately otherwise after this.  Example:    if(step<MinStep) { FATALF("invalid step size: %f",step); ExpertRemove(); return; }
bool	DEBUG (...)  DEBUGF (string format,...)	Messages for DEBUG level.
bool	TRACE (...)  TRACEF (string format,...)	Messages for TRACE (more verbose than DEBUG, for function entries, calculations etc).
string	L4mq.LastMessage()	Get the last message that has been logged.
int	L4mq.LastLevel()	Get the severity level of the last logging event.
int	L4mq.Level()	Get the severity level of the logger.
string	L4mq.LevelAsString()	Get the severity level of the logger as string.
void	L4mq.SetLevel(int)	Set the severity level for the logger.
ulong	L4mq.SeqNr()	Get the sequence number of the last logged event.
bool	L4mq.logged	true if the last event was logged.
string	Log4mql::GetErrorDescription(int err)	Get the description of an error code like _LastError.
string	Log4mql::GetUninitReason(int reason)	Get the description of the uninit reason.
string	Log4mql::LoglevelToString(int level)	Convert a log level to a descriptive string.

Notes

• As the functionality strives to be as simple as possible, there is no logging to files. You could implement some on your own if you want.
• You are free to use this code in your work, however, if you share the source code you must not remove the copyright and license notice.
• The full functionality of Log4mql is available here: https://www.mql5.com/en/code/31425 (MT4) or here: https://www.mql5.com/en/code/31452 (MT5)