Delphi7 - How can i copy a file that is being written to
- by Simon
I have an application that logs information to a daily text file every second on a master PC. A Slave PC on the network using the same application would like to copy this text file to its local drive. I can see there is going to be file access issues.
These files should be no larger than 30-40MB each. the network will be 100MB ethernet. I can see there is potential for the copying process to take longer than 1 second meaning the logging PC will need to open the file for writing while it is being read.
What is the best method for the file writing(logging) and file copying procedures? I know there is the standard Windows CopyFile() procedure, however this has given me file access problems. There is also TFileStream using the fmShareDenyNone flag, but this also very occasionally gives me an access problem too (like 1 per week).
What is this the best way of accomplishing this task?
My current File Logging:
procedure FSWriteline(Filename,Header,s : String);
var LogFile : TFileStream;
line : String;
begin
if not FileExists(filename) then
begin
LogFile := TFileStream.Create(FileName, fmCreate or fmShareDenyNone);
try
LogFile.Seek(0,soFromEnd);
line := Header + #13#10;
LogFile.Write(line[1],Length(line));
line := s + #13#10;
LogFile.Write(line[1],Length(line));
finally
logfile.Free;
end;
end else begin
line := s + #13#10;
Logfile:=tfilestream.Create(Filename,fmOpenWrite or fmShareDenyNone);
try
logfile.Seek(0,soFromEnd);
Logfile.Write(line[1], length(line));
finally
Logfile.free;
end;
end;
end;
My file copy procedure:
procedure DoCopy(infile, Outfile : String);
begin
ForceDirectories(ExtractFilePath(outfile)); //ensure folder exists
if FileAge(inFile) = FileAge(OutFile) then Exit; //they are the same modified time
try
{ Open existing destination }
fo := TFileStream.Create(Outfile, fmOpenReadWrite or fmShareDenyNone);
fo.Position := 0;
except
{ otherwise Create destination }
fo := TFileStream.Create(OutFile, fmCreate or fmShareDenyNone);
end;
try
{ open source }
fi := TFileStream.Create(InFile, fmOpenRead or fmShareDenyNone);
try
cnt:= 0;
fi.Position := cnt;
max := fi.Size;
{start copying }
Repeat
dod := BLOCKSIZE; // Block size
if cnt+dod>max then dod := max-cnt;
if dod>0 then did := fo.CopyFrom(fi, dod);
cnt:=cnt+did;
Percent := Round(Cnt/Max*100);
until (dod=0)
finally
fi.free;
end;
finally
fo.free;
end;
end;
