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Open  
Method  
Opens the specified file for the specified read or write access
File Class
System.IO NameSpace
CF1.  Function Open ( PathString : String; Mode : FileMode; Access : FileAccess; Share : FileShare ) : FileStream; Static;
CF : Methods with this mark are Compact Framework Compatible
Description
Returns a FileStream object configured to suit the file Mode, Access and Share atributes required for the file specified in PathString.
 
These have the following values :
 
FileAccess :
 
Read Read only access
Write Write only access
ReadWrite Read and write access

 
FileMode :
 
Append Append to the end of the file
Create Create as new, or overwrite if it exists
CreateNew Create as new - throws exception if it exists
Open Opens an existing file
OpenOrCreate Cerate as new or open if the file exists
Truncate Open an existing file and reduce to zero bytes

 
FileShare :
 
None Current access is exclusive
Read Others may concurrently read the file
Write Others may concurrently write to the file
ReadWrite Others may concurrently read and write to the file
Inheritable Allows teh file handle to be inherited by child processes
References
FileStream
Microsoft MSDN Links
System.IO
System.IO.File
 Author links

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A simple example
program Project1;
{$APPTYPE CONSOLE}

uses
  System.IO;

var
  Path   : String;
  Stream : System.IO.FileStream;
  MyByte : Integer;

begin
  // Open the file for writing
  Path := 'C:\DelphiBasics.txt';
  Stream := System.IO.File.OpenWrite(path);

  // Write to the file
  Stream.WriteByte(65);  // Chr(65) = 'A'
  Stream.WriteByte(66);  // Chr(66) = 'B'
  Stream.WriteByte(67);  // Chr(67) = 'C'

  // Close the file
  Stream.Close;

  // Re-open for reading
  Stream := System.IO.File.Open(Path,
                                System.IO.FileMode.Open,
                                System.IO.FileAccess.Read,
                                System.IO.FileShare.None);

  // Display the contents
  MyByte := Stream.ReadByte;
  while MyByte >= 0 do
  begin
    Console.Write(Char(MyByte));
    MyByte := Stream.ReadByte;
  end;

  // Close the stream
  Stream.Close;

  Console.Readline;
end.
   ABC
 
 
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