Watch how to download trading robots for free
Find us on Twitter!
Join our fan page
Interesting script?
So post a link to it -
let others appraise it
You liked the script? Try it in the MetaTrader 5 terminal

Log4mql(mini) MT4 - library for MetaTrader 4

2021.01.20 21:55
2021.03.09 03:30
log4mqlm.mqh (40.63 KB) view

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

Sample output MT4


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


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

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

    Log4mql(mini) Inputs

      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.mq4:72): initializing
      WARN %func(%file:%line): %msg
      WARN SomeFunction(log4mqlm_sample.mq4:64): stoploss too tight
      ERROR %func(%file:%line): %msg
      optionally followed by: [, error %lasterr - %lasterrdesc]
      ERROR OnDeinit(log4mqlm_sample.mq4:85): open 'some file' failed,  error 5004 - Cannot open file
       Fatal FATAL ... as above
      FATAL  ...


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

      Return type
      Function name
       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.
       PRINTF (string format,...)
       Like PRINT but prints a formatted message. Same rules as known from PrintFormat apply.
       WARN (...)
       WARNF (string format,...)
       Prints its message if log level is set at least to WARN.
       ERROR (...)
       ERRORF (string format,...)
       Prints its message if log level is at least ERROR. Adds _LastError description if set.
       FATAL (...)
       FATALF (string format,...)
       Like ERROR, but with termination. You should call ExpertRemove() or exit immediately otherwise after this.
         if(step<MinStep) { FATALF("invalid step size: %f",step); ExpertRemove(); return; }
       DEBUG (...)
       DEBUGF (string format,...)
       Messages for DEBUG level.
       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.
       Log4mql::GetUninitReason(int reason)  Get the description of the uninit reason.
       string  Log4mql::LoglevelToString(int level)  Convert a log level to a descriptive string.


      • 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: (MT4) or here: (MT5)

      Corrected moving averages Corrected moving averages

      Corrected moving averages

      The intersections of two lines The intersections of two lines

      In MetaTrader 4, we intend to calculate the intersection coordinates of two straight line objects with different slopes using MQL4.

      The colored volumes (English Version) The colored volumes (English Version)

      Colored volumes at the bottom of the chart

      Breakout Strength Meter - MT4 Breakout Strength Meter - MT4

      The breakout strength meter is a trading tool that is used to identify which currencies are the strongest to breakout, and which currencies are the weakest to breakout