Query regarding 'RenameFile()' procedure

[CHeighlund]

I have a slight problem with the RenameFile procedure(function?) in Delphi, and I'm hoping someone can help me figure out what I'm doing wrong here.

I have a program I wrote that creates a .csv file for output; this file will be picked up by another program later. The .csv-generating program is run once a month. Prior to this, I have simply been allowing the 'current' run to overwrite the 'previous' run. However, due to a recent error (on my part; a change to the program that left part of the output incorrect), my boss has requested that I ensure that there is a one-month's record - that is, that the previous months file not be overwritten with the current one. As the .csv filename has to be hardcoded for the receiving program to catch it, I can't just make a quick change to allow for a different name there. I figured the RenameFile() would allow me to do what I wanted; the example in the Delphi Help pages is almost identical to what I need to do. However, every time I run it, I get the "can't do this" error message.

My code - mostly identical to the sample. Directory and file names (not extensions) have been changed, but that is the only difference between this and my own code.

  progPath:='C:\targetDir\filenm.csv';

  if FileExists(progPath) then
  begin
    BackupName := 'C:\targetDir\filenm.cpy';
    if not RenameFile(progPath, BackupName) then
      raise Exception.Create('Unable to create backup file.');
  end;

Can anyone suggest a reason why my program doesn't seem to be able to rename the file from *.csv to *.cpy? I know the program can write to that directory (it writes the .csv there, after all), so I don't see why I can't get it to rename the previous file. Any suggestions?

 

[Glenn9999]

Is the file currently open by your or another process?

----------
Measurement is not management.

 

[CHeighlund]

Not to my knowledge. The closest thing I can think of is that the program does attempt to open the file a few lines later (for rewriting purposes, hence the need to make the backup). Could that be what's causing the Rename to fail?

 

[Glenn9999]

Okay, think I got it...you can't rename to an existing file...are you deleting the old backup?

----------
Measurement is not management.

 

[whosrdaddy]

ok,

I bet 100$ on the fact that Glenn is correct

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

 

[roo0047]

I tested your code and it works perfectly. The answer to Glenn's question must be "true". Suggest looking further.

the program does attempt to open the file a few lines later

If indeed "false" then there's a good chance that Delphi's speed is causing it to be opened before the system has had a chance to shell out to the rename process.


And yes, it is an external call to Windows:
function MoveFile; external kernel32 name 'MoveFileA';

Try putting a sleep between the two or

while FileExists(progPath) do;

between the Rename and the Open.

Also check that BackupName does not already exist:

begin
  progPath:= 'C:\targetDir\filenm.csv';
  BackupName := 'C:\targetDir\filenm.cpy';
  if not FileExists(BackupName) then
    if FileExists(progPath) then
    begin
      if not RenameFile(progPath, BackupName) then
        raise Exception.Create('Unable to create backup file.');
    end
  else
    raise Exception.Create('BackupName already exists!')
end;

Roo
Delphi Rules!

 

[CHeighlund]

@Glenn9999
Not yet, although I will be, so thanks for the heads-up on that issue. The problem was that I wasn't getting it to work even when there was no backup.

I'm going to try Roo's suggestion and see if that helps clear things up any.