Does ShellExecuteW(…) work only once in MetaTrader 4 or not?

问题

Trying to launch an .exe from MQL4 using ShellExecuteW().

Does this command work only once, or not?

#import "shell32.dll"   // MQL4-syntax-wrapper-Bo[#import]Container
                        // v-------------- caller-side interface to DLL
        int ShellExecuteW( int    hWnd,
                           int    lpVerb,
                           string lpFile,
                           int    lpParameters,
                           int    lpDirectory,
                           int    nCmdShow
                           );
#import                 // MQL4-syntax-wrapper-Eo[#import]Container

if (  cond == true ){
      ShellExecuteW( 0, "open", "D:\\Execute.exe", "", "", 1 );
   }

回答1:

A: a short version

Maybe yes, maybe no.

A: a bit more indepth one [TLDR]

Fact: MT4 Terminal's process-control / process-management is nothing superior, however it allows you to integrate several lines of control over what happens inside ( and outside ... not only via ShellExecuteW(...) ... ) the MT4 Terminal.

MT4 Terminal supports the following processes per graph ( via built-in threads ):

{ 0 | 1 } occurences of a singleton instance called MQL4-ExpertAdvisor
{ 0 | 1 } occurences of a singleton instance called MQL4-Script
{ 0 | 1 ... n } occurences of a functionally restricted instance called MQL4-TechnicalIndicator

The nature of these instances differs in several ways, however in the closest relation to your question, each of the processes have both a mandatory part and a set of arbitrary parts.

Speaking in the original MQL4 ( one may have noticed, that since Build 7xx MQL4 language syntax has moved closer and closer towards MQL5, thus sometimes got labeled as MQL4.5 :o) )

//\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
//
// MQL4 code ----------------------------------------------------------<BoF>------

// MQL4 code compiler directives' section -----------------------<BoS>

#import ...                // MQL4-syntax-wrapper-Bo[#import]Container
        ..
        .
#import                    // MQL4-syntax-wrapper-Eo[#import]Container

// MQL4 code compiler directives' section -----------------------<EoS>

// ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
//
// MQL4 code section ---------------------------- init() / start() / deinit()
//

int init(){    // this part is being run just once,
               //                        right upon an instance activation
   }

int start(){   // this part is being run just once, for an MQL4-Script
               //                        right upon an instance activation
               //                    run upon an FX-MarketEvent is being observed
               //                             in an MQL4-ExpertAdvisor
               //                             or
               //                             in an MQL4-TechnicalIndicator


   }
...
..
.
//
// MQL4 code ---------------------------------------------------------<EoF>------
//
//\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/

So, the exact location of your deployment code, that (re-)uses the generic DLL-service ( #import-ed for both the compile-time alignment and the dynamic linking upon (re-use) decides how many times the external process has been asked to get invoked.

Nota Bene

There are much smarter ways to integrate MT4 Terminal with external processes or remote processes ( Clouds & Grids ) than just a DLL-based spawn of just another blind & deaf unmanageable <localhost> process.

Typically one needs both process-control and bidirectional communication between / among processes.

Do not hesitate to ask more.

MT4 ( with some additional tools ) can do.

来源：https://stackoverflow.com/questions/29779734/does-shellexecutew-work-only-once-in-metatrader-4-or-not

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