MQL5 ReferenceFile FunctionsFileWriteArray

FileWriteArray

The function writes arrays of any type except for string to a BIN file (can be an array of structures not containing strings or dynamic arrays).

uint  FileWriteArray(
   int          file_handle,         // File handle
   const void&  array[],             // Array
   int          start=0,             // Start index in the array
   int          count=WHOLE_ARRAY    // Number of elements
   );

Parameters

file_handle

[in] File descriptor returned by FileOpen().

array[]

[out] Array for recording.

start=0

[in] Initial index in the array (number of the first recorded element).

count=WHOLE_ARRAY

[in] Number of items to write (WHOLE_ARRAY means that all items starting with the number start until the end of the array will be written).

Return Value

Number of recorded items.

Note

String array can be recorded in a TXT file. In this case, strings are automatically ended by the line end characters "\r\n". Depending on the file type ANSI or UNICODE, strings are either converted to ansi-encoding or not.

Example:

//+------------------------------------------------------------------+
//|                                          Demo_FileWriteArray.mq5 |
//|                        Copyright 2013, MetaQuotes Software Corp. |
//|                                              https://www.mql5.com |
//+------------------------------------------------------------------+
#property copyright "Copyright 2013, MetaQuotes Software Corp."
#property link      "https://www.mql5.com"
#property version   "1.00"
//--- input parameters
input string InpFileName="data.bin";
input string InpDirectoryName="SomeFolder";
//+------------------------------------------------------------------+
//| Structure for storing price data                                 |
//+------------------------------------------------------------------+
struct prices
  {
   datetime          date; // date
   double            bid;  // bid price
   double            ask;  // ask price
  };
//--- global variables
int    count=0;
int    size=20;
string path=InpDirectoryName+"//"+InpFileName;
prices arr[];
//+------------------------------------------------------------------+
//| Expert initialization function                                   |
//+------------------------------------------------------------------+
int OnInit()
  {
//--- allocate memory for the array
   ArrayResize(arr,size);
//---
   return(INIT_SUCCEEDED);
  }
//+------------------------------------------------------------------+
//| Expert deinitialization function                                 |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
  {
//--- write the remaining count strings if count<n
   WriteData(count);
  }
//+------------------------------------------------------------------+
//| Expert tick function                                             |
//+------------------------------------------------------------------+
void OnTick()
  {
//--- save data to array
   arr[count].date=TimeCurrent();
   arr[count].bid=SymbolInfoDouble(Symbol(),SYMBOL_BID);
   arr[count].ask=SymbolInfoDouble(Symbol(),SYMBOL_ASK);
//--- show current data
   Print("Date = ",arr[count].date," Bid = ",arr[count].bid," Ask = ",arr[count].ask);
//--- increase the counter
   count++;
//--- if the array is filled, write data to the file and zero it out
   if(count==size)
     {
      WriteData(size);
      count=0;
     }
  }
//+------------------------------------------------------------------+
//| Write n elements of the array to file                            |
//+------------------------------------------------------------------+
void WriteData(const int n)
  {
//--- open the file
   ResetLastError();
   int handle=FileOpen(path,FILE_READ|FILE_WRITE|FILE_BIN);
   if(handle!=INVALID_HANDLE)
     {
      //--- write array data to the end of the file
      FileSeek(handle,0,SEEK_END);
      FileWriteArray(handle,arr,0,n);
      //--- close the file
      FileClose(handle);
     }
   else
      Print("Failed to open the file, error ",GetLastError());
  }