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Global Variable question:

  • #1
  • First Post: Nov 15, 2008 3:41pm Nov 15, 2008 3:41pm
Here is what I want to do:

I have 2 separate mt4 broker terminals open. (Broker A & Broker B)

Broker A has an EA that stores a double value as a global variable. PHP Code:

GlobalVariableSet("Broker_A",Some_Value);


Broker B has an EA that retrieves the global variable stored in Broker A.
PHP Code:

GlobalVariableGet("Broker_A");


Does anyone know a way to do this?
  • #2
  • Nov 15, 2008 4:18pm Nov 15, 2008 4:18pm
you can do it by writing back & forth to a text file. One MT opens it, writes to it and then closes it. The other opens, reads it and closes it. The order of operations is important because you don't want to cause a conflict in the read/writes of the file.
  • #3
  • Nov 15, 2008 5:46pm Nov 15, 2008 5:46pm
Quoting LongToBeFree
you can do it by writing back & forth to a text file. One MT opens it, writes to it and then closes it. The other opens, reads it and closes it. The order of operations is important because you don't want to cause a conflict in the read/writes of the file.
I thought you could only read/write to a text file within each respective mt4 terminal. Could you give an example of how to write to an external file if you have time?

My other concern is the speed at which these operations could be performed. As I understand it, a file can only be open to one application at a time, meaning if an application is currently writing to it, the other application can not access the file until it is closed by the writing application. Is this true?
  • #4
  • Nov 15, 2008 9:23pm Nov 15, 2008 9:23pm
This function is what I use to write useful data into the EA's I created for debugging later cos the journal and the expert tab just ain't good enough.

It merely appends to the file if exist and has data. The file will be created by the FileOpen function if not already available. perhaps u can use this to derive what you need?

Inserted Code
void WriteToLogFile(string input)
{
   string filename = "SSS_EA-"+Symbol()+"-"+Day()+"-"+Month()+"-"+Year()+".log";
   int handle = FileOpen(filename,FILE_READ|FILE_WRITE);
   if (handle>1)
   {
      FileSeek(handle, 0, SEEK_END); // go to end of file
      FileWrite(handle, input);
      FileClose(handle);
   }
}
Programming for a better future.
  • #5
  • Nov 15, 2008 11:28pm Nov 15, 2008 11:28pm
Quoting Zen_Leow
This function is what I use to write useful data into the EA's I created for debugging later cos the journal and the expert tab just ain't good enough.

It merely appends to the file if exist and has data. The file will be created by the FileOpen function if not already available. perhaps u can use this to derive what you need?

[code]
void WriteToLogFile(string input)
{...
Thank you Zen_Leow,

I will try to to use your example and learn from it.

I appreciate your help.

-wolfe
  • #6
  • Nov 16, 2008 12:44pm Nov 16, 2008 12:44pm
Lots of information here: http://articles.mql4.com/720
  • #7
  • Nov 16, 2008 2:33pm Nov 16, 2008 2:33pm
Quoting NthDegreeDbf
Lots of information here: http://articles.mql4.com/720
Thank you,

I'll check out the link.
  • #8
  • Last Post: Nov 16, 2008 2:41pm Nov 16, 2008 2:41pm
Here's a good article on the interaction of globals in multiple EA's on one client.

http://book.mql4.com/variables/globals
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