Overwrite files in a Folder / SubFolder (Very Urgent)

The question you need to address is "how do you know when the drive is full", presumably the files are of varying size, so you cannot predict when another file will be able to fit on the drive or not.

I would suggest you change you strategy slightly and have a configuration setting, such as
"Keep files for X days"

You can then just do a file search, decode the date, compare it to the current date, and if it is over the setting then delete the file

Hello Sir,

  Thanks for your reply, but it would like to have some sample code to do the same.

with regards,
padmaja.

Somehting like this

procedure TForm1.DeleteFiles(Directory: string; DaysOld: integer);
var
  sr: TSearchRec;
  FileAttrs: Integer;
  ltDate: TDate;
  lDay: word;
  lMonth: word;
  lYear: word;
  procedure CheckAndDelete;
  begin
    lDay:=StrToInt(Copy(sr.Name,1,2));
    lMonth:=StrToInt(Copy(sr.Name,3,2));
    lYear:=StrToInt(Copy(sr.Name,5,4));
    ltDate:=EncodeDate(lYear,lMonth,lDay);
    if ltDate<Date()-DaysOld then
      DeleteFile(Directory+'\'+sr.Name);
  end;
begin
  if FindFirst(Directory+'\*.avi', faAnyFile, sr) = 0 then
  begin
    CheckAndDelete;
    while FindNext(sr) = 0 do
      CheckAndDelete;
    FindClose(sr);
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  DeleteFiles('c:\test1\camera1',7);
end;

This code woul delete any avi file from c:\test1\camera1' over 7 days old

could do with some error checking, but you should get the idea

regards

you said "any help is appreciated", i dont like puretype code hunters :/
however, in contrast to pcsentinels solution this one will determine the oldest file and ask you to delete it:


procedure ScanDir(sPath: string; var sOldest: string; var tOldest: filetime);
var
  h1: thandle;
  wfd: win32_find_data;
begin
  h1:= findfirstfile(PChar(sPath+ '*.*'), wfd);
  if h1= invalid_handle_value then exit;

  repeat
    if wfd.dwFileAttributes and file_attribute_directory<> 0 then begin
      if (strpas(wfd.cFileName)<> '.') and (strpas(wfd.cFileName)<> '..') then ScanDir(sPath+ wfd.cFileName+ '\', sOldest, tOldest);
    end else begin
      if CompareFileTime(wfd.ftCreationTime, tOldest)< 0 then begin
        tOldest:= wfd.ftCreationTime;
        sOldest:= sPath+ wfd.cFileName;
      end;
    end;
  until not findnextfile(h1, wfd);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  t1: filetime;
  s1: string;
begin
  GetSystemTimeAsFileTime(t1);
  s1:= '';
  ScanDir('D:\', s1, t1);
  if s1<> '' then begin
    if MessageBox(0, pchar('Oldest file is:'#13+ s1+ #13#13+ 'Delete it?'), 'info', mb_iconquestion or mb_yesno or mb_defbutton2)= idyes then deletefile(s1);
  end else MessageBox(0, 'no file found', nil, mb_iconstop);
end;

Hello Sir,

   Thanks for your replies. I was a bit busy and could not reply. I would like to know if I could check for diskfull or may be once say about 10% of the disk is empty start overwriting on the existing files. I have to look into the performance as well. Or is there a way wherein my application is notified when the disk is 10% empty. Even if there is any VCL which could do this without affecting the performance I shall be greatful.

with regards,
padmaja.

no.

any application itself has to make the request. it can look on how much bytes are filled on the disk - and so calculate if less than 10% are free. this request has to be made again and again, like with a timer.

whatever you need, it will need performance as well. the check for the 10% wont affect too much (consider it making all 2mins, its nothing to the systems resources). but once the decision is made to delete files the work comes: how should the files be deleted? if the oldest should be, then the whole disk has to be listed in order to find the oldest files. then all files can be sorted (i hope theyre a small sum, like 200 orso). making a file list has the advantage that the whole file listing through the disk has to be made only once instead of always again until more than 10% are free again. the disadvantages are the result list itself, which will consume memory and the more cpu time which is needed to sort this list (so we can delete file after file until more than 10% are free again).

Hello Sir,

  Thanks for your reply. How about overwriting instead of deleting. Just a suggesstion. What is the effect of performance in either cases (deletion and overwriting).

with regards,
padmaja.

"Each day it creates a new folder like 07092006 under respective cameras and records the avi files" - how should "overwriting" work here? im not sure if we understand the same by the word "overwriting" - for me it means that a file is not being deleted, but its inner bytes are being altered, not changing the filesize itself. no matter which video format you are recording, it would surely not work because most videos have headers and indexes - so each of those files must be complete on their own.

i sum up:
- you are (quite randomly) saving large files
- you dont know how big they will be, so
- you cannot forecast if the remaining disk space will suffice your needs

if you want a FIFO-system, then you should have an application which always maintains a list of every created file (of course this means you are not allowed to manually delete/create files on that harddrive). whenever you want to create a file, you simply do the following:
- is the remaining diskspace large enough? (what IS large enough for you?) if not then
- get the first mentioned file of the list (should be the oldest),
- delete it
- repeat this process (go back to the first of these points)
- finally create the new file and add the filename at the bottom of the list

this solution would be very good for perfomance reasons, because we dont have to list the files of the drive again and again (since we maintain the filelist weve created) and it is also not timer-dependent. it is only triggered once you want to create another file. the first run of this application of course has to do a one-time dir listing in order to realize the current scenario on the disk.

Hello Sir,

   Thanks for the reply. Do you think that I need to write it as a separate thread or an entire application which runs along with the main which will do the above tasks. Which would be better, because I need to continuously record the 4 cameras between the given time and a new file to be created for each of the 4 for every half an hour.

with regards,
padmaja.