Need to open TextFile -ReadOnly with other app running

[StuM]

I am trying to get read only access to a .CSV file that is currently open with another application that is filling it.

AssignFile(FF, CSVFile);
FileMode:= fmopenread;
Reset(FF);

Error 103 is returned.

If the other application is closed and MY app is started the file opens OK. If I then start the other App, everything works OK until MY app trys to reopen the file.

I have tried different values for "FileMode" for Sharing with no success. The "Other Application" and Excel have the same effect on my program (Error 103).

 

[Glenn9999]

I'm not sure you're doing the file access properly (at least not for the Delphi I'm running - the constant works but I'm not finding it). What I've been doing is

filemode := 0; {read only}
assign(infile, 'mydata.csv');
reset(infile);

and it works like you're looking for it to work.

But anyway, if the other app expects to have the file in read/write mode, it will generally lock the file to anything but readonly access, and vice versa. For example, if I set filemode to 1, then the file can only be pulled up in read-only mode.

If it helps, you should be able to typecast "infile" with TFileRec, and access "handle" and then double-check what mode you have the file in (fmClosed, fmInput, fmOutput, or fmInOut)

 

[StuM]

I'm using Version 7 of Delphi

Looking at my Delphi help -"Note:To avoid scope conflicts, AssignFile replaces the Assign procedure that was available in early versions of the Delphi product. However, for backward compatibility Assign is still available.

I tried moving the filemode statement before the assign and that didn't help.

FmOpenRead is found in the help under "File open mode constants".

 

[Griffyn]

You can't always open a file in read-only mode that is open for writing by another program. There's more to it than ReadOnly and ReadWrite access. There's also sharing.

Generally, a program that opens a file in ReadWrite mode also opens it in Exclusive mode - this is the bane of backup programs everywhere.

You need to modify the other app to open the file with sharing enabled, ie. fmReadWrite+fmShareDenyNone or fmReadWrite+fmShareDenyWrite

 

[StuM]

The other program (not written in house) works with Excel opening it for "read-only".... So wouldn't that mean that it "should be" ok for my delphi program to open it ?

 

[whosrdaddy]

Stum, try adding fmShareDenyNone as Griffyn suggested:
...
FileMode:= fmopenread + fmShareDenyNone;
...


-----------------------------------------------------
What You See Is What You Get
Never underestimate tha powah of tha google!

 

[StuM]

I already tried that. Since Excel can open the CSV, after I click on the "Read-Only" message that comes up, doesn't that mean that the "other app" is set-up properly for file sharing, AND I just need to get the correct setting in Delphi,(my program), to open it ?

 

[roo0047]

Have you thought about doing something like this:

  AssignFile(FF, 'mydata.csv');
  {$I-}
  Reset(FF);
  {$I+}
  if IOResult <> 0 then begin
    CopyFile('mydata.csv', 'mydata[1].csv', false);
    AssignFile(FF, 'mydata[1].csv');
    Reset(FF);
  end;

Untested, and there's more you could do to make it idiot proof, but just enough to hopefully give you an idea to work with...

Roo
Delphi Rules!

 

[StuM]

I found the solution. The Filemode DOESN'T WORK with TEXTFILE

VAR
XX,Data1 : String;
TF : TextFile;
begin

XX:='C:\FEEventsM20070919.csv';
AssignFile(TF,XX);
OpenReadText(TF,False);
reset(TF);
Readln(TF,Data1);
Showmessage(Data1);

CloseFile(TF);

Change to:

Var
S: TFileStream;
FNM,Data1 : String;

begin
FNM:='c:\FEEventsM20070919.csv';
S:= TfileStream.Create(FNM,fmOpenRead + fmShareDenyNone );

try
Memo1.Lines.LoadFromStream(S);
Finally
S.Free;
end;
end;

Now I just have to figure out how to load data into Strings, one line at a time.

Thanks for the help.

 

[Griffyn]

You should be able to copy the TFileStream to a TStringStream

 

[roo0047]

You already have, if you have it in a Memo.

  for i:= 0 to Memo1.Lines.Count -1 do
    showMessage('Line[' + intToStr(i) + '] = ' + Memo1.Lines[i];

Roo
Delphi Rules!