System.IOResult Function

Returns the status of the last I/O operation performed.

Pascal

function IOResult: Integer;

C++

int IOResult();

File

System

Description

IOResult returns the result of the last Delphi I/O routine when I/O-checking is off (that is, when using the {$I-} compiler option). If IOResult returns 0, the last I/O operation succeeded. Otherwise, IOResult returns an error code.

If an I/O error occurs and I/O-checking is off, all subsequent I/O operations are ignored until the internal error flag is cleared. Calling IOResult clears the internal error flag.

An alternative way to handle I/O errors is to use exception handling with the {$I+} compiler option.

Delphi Examples:

Copy Code

{
IOResult example
This example illustrates how to use IOResult to check the success of the Reset
method. If the call to Reset is successful, a message dialog displays the size
of the file that the user selects in an Open dialog. If the call to Reset fails,
a message warns the user that there was a file access error. To test the failure
part of this example, just misspell a file name in the open dialog.
}
procedure TForm1.Button1Click(Sender: TObject);
var
  F: File of Byte;
begin
  if OpenDialog1.Execute then
  begin
    AssignFile(F, OpenDialog1.FileName);
    {$I-}
    Reset(F);
    {$I+}
    if IOResult = 0 then
    begin
      MessageDlg('File size in bytes: ' + IntToStr(FileSize(F)),
        mtInformation, [mbOk], 0);
      CloseFile(F);
    end
    else
      MessageDlg('File access error', mtWarning, [mbOk], 0);
  end;
end;

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