Problum in reading text file

salirazataqvi 2018.03.02 20:49

Hi all I am trying to read text file using MQL4. the issue I am facing is FileReadString method always returns empty string. following is my code:

void OnTick()
{
      Read();

}


void Read()
{
   ResetLastError(); 
   
   int file_handle = FileOpen("investing_technical_technical-summary.txt", FILE_READ|FILE_BIN|FILE_ANSI); 
   
   if(file_handle!=INVALID_HANDLE) 
   { 
      PrintFormat("%s file is available for reading", "investing_technical_technical-summary.txt");      
      
      int    str_size; 
      string str; 
      
      while(!FileIsEnding(file_handle)) 
      { 
         str_size=FileReadInteger(file_handle, INT_VALUE); 
         
         str=FileReadString(file_handle);
         
         Print(str);
      } 
      
      FileClose(file_handle); 
      
      PrintFormat("Data is read, %s file is closed", "investing_technical_technical-summary.txt");
   } 
   else 
      PrintFormat("Failed to open %s file, Error code = %d", "investing_technical_technical-summary.txt", GetLastError()); 
}

William Roeder 2018.03.02 21:11 #1

salirazataqvi: I am trying to read text file using MQL4. the issue I am facing is FileReadString method always returns empty string. following is my code:

 int file_handle = FileOpen("investing_technical_technical-summary.txt", FILE_READ|FILE_BIN|FILE_ANSI);

You aren't reading a text file.

Perhaps you should read the manual.
When reading from a bin-file. the length of a string to read must be specified.
FileReadString - File Functions - MQL4 Reference

salirazataqvi 2018.03.03 08:33 #2

Thanks whroeder1,

I have changed my code as follows but still not able to read file. I am getting 5004 Error code.

void OnTick()
{
      Read();
}

void Read()
{
   ResetLastError(); 
   
   int file_handle = FileOpen("investing_technical_technical-summary.txt", FILE_READ|FILE_TXT); 
   
   if(file_handle!=INVALID_HANDLE) 
   { 
      PrintFormat("%s file is available for reading", "investing_technical_technical-summary.txt");      
      
      int    str_size; 
      string str; 
      
      while(!FileIsEnding(file_handle)) 
      { 
         str_size=FileReadInteger(file_handle, INT_VALUE); 
         
         str=FileReadString(file_handle);
         
         Print(str);
      } 
      
      FileClose(file_handle); 
      
      PrintFormat("Data is read, %s file is closed", "investing_technical_technical-summary.txt");
   } 
   else 
      PrintFormat("Failed to open %s file, Error code = %d", "investing_technical_technical-summary.txt", GetLastError()); 
}

Marco vd Heijden 2018.03.03 09:40 #3

It's still wrong go read that documentation.

Function	Action
FileFindFirst	Starts the search of files in a directory in accordance with the specified filter
FileFindNext	Continues the search started by the FileFindFirst() function
FileFindClose	Closes search handle
FileOpen	Opens a file with a specified name and flag
FileDelete	Deletes a specified file
FileFlush	Writes to a disk all data remaining in the input/output file buffer
FileGetInteger	Gets an integer property of a file
FileIsEnding	Defines the end of a file in the process of reading
FileIsLineEnding	Defines the end of a line in a text file in the process of reading
FileClose	Closes a previously opened file
FileIsExist	Checks the existence of a file
FileCopy	Copies the original file from a local or shared folder to another file
FileMove	Moves or renames a file
FileReadArray	Reads arrays of any type except for string from the file of the BIN type
FileReadBool	Reads from the file of the CSV type a string from the current position till a delimiter (or till the end of a text line) and converts the read string to a value of bool type
FileReadDatetime	Reads from the file of the CSV type a string of one of the formats: "YYYY.MM.DD HH:MM:SS", "YYYY.MM.DD" or "HH:MM:SS" - and converts it into a datetime value
FileReadDouble	Reads a double value from the current position of the file pointer
FileReadFloat	Reads a float value from the current position of the file pointer
FileReadInteger	Reads int, short or char value from the current position of the file pointer
FileReadLong	Reads a long type value from the current position of the file pointer
FileReadNumber	Reads from the file of the CSV type a string from the current position till a delimiter (or til the end of a text line) and converts the read string into double value
FileReadString	Reads a string from the current position of a file pointer from a file
FileReadStruct	Reads the contents from a binary file into a structure passed as a parameter, from the current position of the file pointer
FileSeek	Moves the position of the file pointer by a specified number of bytes relative to the specified position
FileSize	Returns the size of a corresponding open file
FileTell	Returns the current position of the file pointer of a corresponding open file
FileWrite	Writes data to a file of CSV or TXT type
FileWriteArray	Writes arrays of any type except for string into a file of BIN type
FileWriteDouble	Writes value of the double type from the current position of a file pointer into a binary file
FileWriteFloat	Writes value of the float type from the current position of a file pointer into a binary file
FileWriteInteger	Writes value of the int type from the current position of a file pointer into a binary file
FileWriteLong	Writes value of the long type from the current position of a file pointer into a binary file
FileWriteString	Writes the value of a string parameter into a BIN or TXT file starting from the current position of the file pointer
FileWriteStruct	Writes the contents of a structure passed as a parameter into a binary file, starting from the current position of the file pointer
FileLoad	Reads all data of a specified binary file into a passed array of numeric types or simple structures
FileSave	Writes to a binary file all elements of an array passed as a parameter
FolderCreate	Creates a folder in the Files directory
FolderDelete	Removes a selected directory. If the folder is not empty, then it can't be removed
FolderClean	Deletes all files in the specified folder

If the file is opened for writing using FileOpen(), all subfolders specified in the path will be created if there are no such ones.

File Functions how to retain variable How to replace CR

William Roeder 2018.03.03 14:29 #4

salirazataqvi: I have changed my code as follows but still not able to read file. I am getting 5004 Error code.

You changed the open from binary to text. You didn't change the reading code.
FileReadInteger is for reading binary files. You're not. Try number.
You opened a TXT file, you can't split lines while reading. Try CSV with a separator. Only you know what is in your file.
You know what the error is. There is no such file in MQL4\Files or tester\files.

Invalid Handle Any questions from newcomers From a file to

salirazataqvi 2018.03.03 17:06 #5

Thanks All,

I managed to solved the issue and red the file via same code. The issue was file was not at the correct location as you mentioned in 4 point. I put the file at the location and issue resolved.

I was getting 5004 error and its description written in the documentation is:

5004

ERR_FILE_CANNOT_OPEN

Cannot open file

I must say documentation provided for MQL is extremely pathetic and most of the time misleading.

FileOpen works in script Error Code 5004 Indicator - Error code

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