Delphi Basics : Reset command

DelphiBasics

Reset
Procedure

Open a text file for reading, or binary file for read/write

System unit

1	procedure Reset(var FileHandle TextFile);
2	procedure Reset (var FileHandle File {RecordSize ;

Description

The Reset procedure opens a file given by FileHandle for read, write or read and write access.

You must use AssignFile to assign a file to the FileHandle before using Reset.

Use Write or WriteLn to write to the file after this Reset is executed.

Version 1

Is used for text files. They can only be read after opening with Reset.

Version 2

Is for binary files. Before using Reset, you must set FileMode to one of the following:

fmOpenRead	: Read only
fmOpenWrite	: Write only
fmOpenReadWrite	: Read and write

The optional RecordSize value is used to override the default 128 byte record size for binary (untyped) files. For such files, only BlockRead and BlockWrite can be used.

Related commands

Append		Open a text file to allow appending of text to the end
AssignFile		Assigns a file handle to a binary or text file
CloseFile		Closes an open file
File		Defines a typed or untyped file
ReWrite		Open a text or binary file for write access
TextFile		Declares a file type for storing lines of text

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Example code : Writing and reading lines of text to/from a text file

var
  myFile : TextFile;
  text   : string;

begin
  // Try to open the Test.txt file for writing to
  AssignFile(myFile, 'Test.txt');
  ReWrite(myFile);

  // Write a couple of well known words to this file
  WriteLn(myFile, 'Hello');
  WriteLn(myFile, 'World');

  // Close the file
  CloseFile(myFile);

  // Reopen the file in read only mode
  FileMode := fmOpenRead;
  Reset(myFile);

  // Display the file contents
  while not Eof(myFile) do
  begin
    ReadLn(myFile, text);
    ShowMessage(text);
  end;

  // Close the file for the last time
  CloseFile(myFile);
end;

Show full unit code

Hello
World